Lazy Series¶
Coefficients of lazy series are computed on demand. They have infinite precision, although equality can only be decided in special cases.
AUTHORS:
Kwankyu Lee (2019-02-24): initial version
Tejasvi Chebrolu, Martin Rubey, Travis Scrimshaw (2021-08): refactored and expanded functionality
EXAMPLES:
Laurent series over the integer ring are particularly useful as generating functions for sequences arising in combinatorics.
sage: L.<z> = LazyLaurentSeriesRing(ZZ)
>>> from sage.all import *
>>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1)
L.<z> = LazyLaurentSeriesRing(ZZ)
The generating function of the Fibonacci sequence is:
sage: f = 1 / (1 - z - z^2)
sage: f
1 + z + 2*z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7)
>>> from sage.all import *
>>> f = Integer(1) / (Integer(1) - z - z**Integer(2))
>>> f
1 + z + 2*z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7)
f = 1 / (1 - z - z^2) f
In principle, we can now compute any coefficient of \(f\):
sage: f.coefficient(100)
573147844013817084101
>>> from sage.all import *
>>> f.coefficient(Integer(100))
573147844013817084101
f.coefficient(100)
Which coefficients are actually computed depends on the type of implementation. For the sparse implementation, only the coefficients which are needed are computed.
sage: s = L(lambda n: n, valuation=0); s
z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7)
sage: s.coefficient(10)
10
sage: s._coeff_stream._cache
{1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 6: 6, 10: 10}
>>> from sage.all import *
>>> s = L(lambda n: n, valuation=Integer(0)); s
z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7)
>>> s.coefficient(Integer(10))
10
>>> s._coeff_stream._cache
{1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 6: 6, 10: 10}
s = L(lambda n: n, valuation=0); s s.coefficient(10) s._coeff_stream._cache
Using the dense implementation, all coefficients up to the required coefficient are computed.
sage: L.<x> = LazyLaurentSeriesRing(ZZ, sparse=False)
sage: s = L(lambda n: n, valuation=0); s
x + 2*x^2 + 3*x^3 + 4*x^4 + 5*x^5 + 6*x^6 + O(x^7)
sage: s.coefficient(10)
10
sage: s._coeff_stream._cache
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> from sage.all import *
>>> L = LazyLaurentSeriesRing(ZZ, sparse=False, names=('x',)); (x,) = L._first_ngens(1)
>>> s = L(lambda n: n, valuation=Integer(0)); s
x + 2*x^2 + 3*x^3 + 4*x^4 + 5*x^5 + 6*x^6 + O(x^7)
>>> s.coefficient(Integer(10))
10
>>> s._coeff_stream._cache
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
L.<x> = LazyLaurentSeriesRing(ZZ, sparse=False) s = L(lambda n: n, valuation=0); s s.coefficient(10) s._coeff_stream._cache
We can do arithmetic with lazy power series:
sage: f
1 + z + 2*z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7)
sage: f^-1
1 - z - z^2 + O(z^7)
sage: f + f^-1
2 + z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7)
sage: g = (f + f^-1)*(f - f^-1); g
4*z + 6*z^2 + 8*z^3 + 19*z^4 + 38*z^5 + 71*z^6 + O(z^7)
>>> from sage.all import *
>>> f
1 + z + 2*z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7)
>>> f**-Integer(1)
1 - z - z^2 + O(z^7)
>>> f + f**-Integer(1)
2 + z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7)
>>> g = (f + f**-Integer(1))*(f - f**-Integer(1)); g
4*z + 6*z^2 + 8*z^3 + 19*z^4 + 38*z^5 + 71*z^6 + O(z^7)
f f^-1 f + f^-1 g = (f + f^-1)*(f - f^-1); g
We call lazy power series whose coefficients are known to be eventually constant ‘exact’. In some cases, computations with such series are much faster. Moreover, these are the series where equality can be decided. For example:
sage: L.<z> = LazyPowerSeriesRing(ZZ)
sage: f = 1 + 2*z^2 / (1 - z)
sage: f - 2 / (1 - z) + 1 + 2*z
0
>>> from sage.all import *
>>> L = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1)
>>> f = Integer(1) + Integer(2)*z**Integer(2) / (Integer(1) - z)
>>> f - Integer(2) / (Integer(1) - z) + Integer(1) + Integer(2)*z
0
L.<z> = LazyPowerSeriesRing(ZZ) f = 1 + 2*z^2 / (1 - z) f - 2 / (1 - z) + 1 + 2*z
However, multivariate Taylor series are actually represented as streams of multivariate polynomials. Therefore, the only exact series in this case are polynomials:
sage: L.<x,y> = LazyPowerSeriesRing(ZZ)
sage: 1 / (1-x)
1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + O(x,y)^7
>>> from sage.all import *
>>> L = LazyPowerSeriesRing(ZZ, names=('x', 'y',)); (x, y,) = L._first_ngens(2)
>>> Integer(1) / (Integer(1)-x)
1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + O(x,y)^7
L.<x,y> = LazyPowerSeriesRing(ZZ) 1 / (1-x)
A similar statement is true for lazy symmetric functions:
sage: h = SymmetricFunctions(QQ).h() # needs sage.combinat
sage: L = LazySymmetricFunctions(h) # needs sage.combinat
sage: 1 / (1-L(h[1])) # needs sage.combinat
h[] + h[1] + (h[1,1]) + (h[1,1,1]) + (h[1,1,1,1]) + (h[1,1,1,1,1]) + (h[1,1,1,1,1,1]) + O^7
>>> from sage.all import *
>>> h = SymmetricFunctions(QQ).h() # needs sage.combinat
>>> L = LazySymmetricFunctions(h) # needs sage.combinat
>>> Integer(1) / (Integer(1)-L(h[Integer(1)])) # needs sage.combinat
h[] + h[1] + (h[1,1]) + (h[1,1,1]) + (h[1,1,1,1]) + (h[1,1,1,1,1]) + (h[1,1,1,1,1,1]) + O^7
h = SymmetricFunctions(QQ).h() # needs sage.combinat L = LazySymmetricFunctions(h) # needs sage.combinat 1 / (1-L(h[1])) # needs sage.combinat
We can change the base ring:
sage: h = g.change_ring(QQ)
sage: h.parent() # needs sage.combinat
Lazy Laurent Series Ring in z over Rational Field
sage: h # needs sage.combinat
4*z + 6*z^2 + 8*z^3 + 19*z^4 + 38*z^5 + 71*z^6 + 130*z^7 + O(z^8)
sage: hinv = h^-1; hinv # needs sage.combinat
1/4*z^-1 - 3/8 + 1/16*z - 17/32*z^2 + 5/64*z^3 - 29/128*z^4 + 165/256*z^5 + O(z^6)
sage: hinv.valuation() # needs sage.combinat
-1
>>> from sage.all import *
>>> h = g.change_ring(QQ)
>>> h.parent() # needs sage.combinat
Lazy Laurent Series Ring in z over Rational Field
>>> h # needs sage.combinat
4*z + 6*z^2 + 8*z^3 + 19*z^4 + 38*z^5 + 71*z^6 + 130*z^7 + O(z^8)
>>> hinv = h**-Integer(1); hinv # needs sage.combinat
1/4*z^-1 - 3/8 + 1/16*z - 17/32*z^2 + 5/64*z^3 - 29/128*z^4 + 165/256*z^5 + O(z^6)
>>> hinv.valuation() # needs sage.combinat
-1
h = g.change_ring(QQ) h.parent() # needs sage.combinat h # needs sage.combinat hinv = h^-1; hinv # needs sage.combinat hinv.valuation() # needs sage.combinat
- class sage.rings.lazy_series.LazyCauchyProductSeries(parent, coeff_stream)[source]¶
Bases:
LazyModuleElementA class for series where multiplication is the Cauchy product.
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: f = 1 / (1 - z) sage: f 1 + z + z^2 + O(z^3) sage: f * (1 - z) 1 sage: L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) sage: f = 1 / (1 - z) sage: f 1 + z + z^2 + O(z^3)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> f = Integer(1) / (Integer(1) - z) >>> f 1 + z + z^2 + O(z^3) >>> f * (Integer(1) - z) 1 >>> L = LazyLaurentSeriesRing(ZZ, sparse=True, names=('z',)); (z,) = L._first_ngens(1) >>> f = Integer(1) / (Integer(1) - z) >>> f 1 + z + z^2 + O(z^3)
L.<z> = LazyLaurentSeriesRing(ZZ) f = 1 / (1 - z) f f * (1 - z) L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) f = 1 / (1 - z) f
- exp()[source]¶
Return the exponential series of
self.We use the identity
\[\exp(s) = 1 + \int s' \exp(s).\]EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: exp(z) 1 + z + 1/2*z^2 + 1/6*z^3 + 1/24*z^4 + 1/120*z^5 + 1/720*z^6 + O(z^7) sage: exp(z + z^2) 1 + z + 3/2*z^2 + 7/6*z^3 + 25/24*z^4 + 27/40*z^5 + 331/720*z^6 + O(z^7) sage: exp(0) # needs sage.symbolic 1 sage: exp(1 + z) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: exp(x+y)[4].factor() (1/24) * (x + y)^4 sage: exp(x/(1-y)).polynomial(3) 1/6*x^3 + x^2*y + x*y^2 + 1/2*x^2 + x*y + x + 1
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> exp(z) 1 + z + 1/2*z^2 + 1/6*z^3 + 1/24*z^4 + 1/120*z^5 + 1/720*z^6 + O(z^7) >>> exp(z + z**Integer(2)) 1 + z + 3/2*z^2 + 7/6*z^3 + 25/24*z^4 + 27/40*z^5 + 331/720*z^6 + O(z^7) >>> exp(Integer(0)) # needs sage.symbolic 1 >>> exp(Integer(1) + z) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> exp(x+y)[Integer(4)].factor() (1/24) * (x + y)^4 >>> exp(x/(Integer(1)-y)).polynomial(Integer(3)) 1/6*x^3 + x^2*y + x*y^2 + 1/2*x^2 + x*y + x + 1
L.<z> = LazyLaurentSeriesRing(QQ) exp(z) exp(z + z^2) exp(0) # needs sage.symbolic exp(1 + z) L.<x,y> = LazyPowerSeriesRing(QQ) exp(x+y)[4].factor() exp(x/(1-y)).polynomial(3)
- log()[source]¶
Return the series for the natural logarithm of
self.We use the identity
\[\log(s) = \int s' / s.\]EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: log(1/(1-z)) z + 1/2*z^2 + 1/3*z^3 + 1/4*z^4 + 1/5*z^5 + 1/6*z^6 + 1/7*z^7 + O(z^8) sage: L.<x, y> = LazyPowerSeriesRing(QQ) sage: log((1 + x/(1-y))).polynomial(3) 1/3*x^3 - x^2*y + x*y^2 - 1/2*x^2 + x*y + x
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> log(Integer(1)/(Integer(1)-z)) z + 1/2*z^2 + 1/3*z^3 + 1/4*z^4 + 1/5*z^5 + 1/6*z^6 + 1/7*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> log((Integer(1) + x/(Integer(1)-y))).polynomial(Integer(3)) 1/3*x^3 - x^2*y + x*y^2 - 1/2*x^2 + x*y + x
L.<z> = LazyLaurentSeriesRing(QQ) log(1/(1-z)) L.<x, y> = LazyPowerSeriesRing(QQ) log((1 + x/(1-y))).polynomial(3)
- valuation()[source]¶
Return the valuation of
self.This method determines the valuation of the series by looking for a nonzero coefficient. Hence if the series happens to be zero, then it may run forever.
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: s = 1/(1 - z) - 1/(1 - 2*z) sage: s.valuation() 1 sage: t = z - z sage: t.valuation() +Infinity sage: M = L(lambda n: n^2, 0) sage: M.valuation() 1 sage: (M - M).valuation() +Infinity
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> s = Integer(1)/(Integer(1) - z) - Integer(1)/(Integer(1) - Integer(2)*z) >>> s.valuation() 1 >>> t = z - z >>> t.valuation() +Infinity >>> M = L(lambda n: n**Integer(2), Integer(0)) >>> M.valuation() 1 >>> (M - M).valuation() +Infinity
L.<z> = LazyLaurentSeriesRing(ZZ) s = 1/(1 - z) - 1/(1 - 2*z) s.valuation() t = z - z t.valuation() M = L(lambda n: n^2, 0) M.valuation() (M - M).valuation()
- class sage.rings.lazy_series.LazyCompletionGradedAlgebraElement(parent, coeff_stream)[source]¶
Bases:
LazyCauchyProductSeriesAn element of a completion of a graded algebra that is computed lazily.
- class sage.rings.lazy_series.LazyDirichletSeries(parent, coeff_stream)[source]¶
Bases:
LazyModuleElementA Dirichlet series where the coefficients are computed lazily.
EXAMPLES:
sage: L = LazyDirichletSeriesRing(ZZ, "z") sage: f = L(constant=1)^2 sage: f # needs sage.symbolic 1 + 2/2^z + 2/3^z + 3/4^z + 2/5^z + 4/6^z + 2/7^z + O(1/(8^z)) sage: f.coefficient(100) == number_of_divisors(100) # needs sage.libs.pari True
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(ZZ, "z") >>> f = L(constant=Integer(1))**Integer(2) >>> f # needs sage.symbolic 1 + 2/2^z + 2/3^z + 3/4^z + 2/5^z + 4/6^z + 2/7^z + O(1/(8^z)) >>> f.coefficient(Integer(100)) == number_of_divisors(Integer(100)) # needs sage.libs.pari True
L = LazyDirichletSeriesRing(ZZ, "z") f = L(constant=1)^2 f # needs sage.symbolic f.coefficient(100) == number_of_divisors(100) # needs sage.libs.pari
Lazy Dirichlet series is picklable:
sage: g = loads(dumps(f)) sage: g # needs sage.symbolic 1 + 2/2^z + 2/3^z + 3/4^z + 2/5^z + 4/6^z + 2/7^z + O(1/(8^z)) sage: g == f True
>>> from sage.all import * >>> g = loads(dumps(f)) >>> g # needs sage.symbolic 1 + 2/2^z + 2/3^z + 3/4^z + 2/5^z + 4/6^z + 2/7^z + O(1/(8^z)) >>> g == f True
g = loads(dumps(f)) g # needs sage.symbolic g == f
- is_unit()[source]¶
Return whether this element is a unit in the ring.
EXAMPLES:
sage: D = LazyDirichletSeriesRing(ZZ, "s") sage: D([0, 2]).is_unit() False sage: D([-1, 2]).is_unit() True sage: D([3, 2]).is_unit() False sage: D = LazyDirichletSeriesRing(QQ, "s") sage: D([3, 2]).is_unit() True
>>> from sage.all import * >>> D = LazyDirichletSeriesRing(ZZ, "s") >>> D([Integer(0), Integer(2)]).is_unit() False >>> D([-Integer(1), Integer(2)]).is_unit() True >>> D([Integer(3), Integer(2)]).is_unit() False >>> D = LazyDirichletSeriesRing(QQ, "s") >>> D([Integer(3), Integer(2)]).is_unit() True
D = LazyDirichletSeriesRing(ZZ, "s") D([0, 2]).is_unit() D([-1, 2]).is_unit() D([3, 2]).is_unit() D = LazyDirichletSeriesRing(QQ, "s") D([3, 2]).is_unit()
- valuation()[source]¶
Return the valuation of
self.This method determines the valuation of the series by looking for a nonzero coefficient. Hence if the series happens to be zero, then it may run forever.
EXAMPLES:
sage: L = LazyDirichletSeriesRing(ZZ, "z") sage: mu = L(moebius); mu.valuation() # needs sage.libs.pari 0 sage: (mu - mu).valuation() # needs sage.libs.pari +Infinity sage: g = L(constant=1, valuation=2) sage: g.valuation() # needs sage.symbolic log(2) sage: (g*g).valuation() # needs sage.symbolic 2*log(2)
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(ZZ, "z") >>> mu = L(moebius); mu.valuation() # needs sage.libs.pari 0 >>> (mu - mu).valuation() # needs sage.libs.pari +Infinity >>> g = L(constant=Integer(1), valuation=Integer(2)) >>> g.valuation() # needs sage.symbolic log(2) >>> (g*g).valuation() # needs sage.symbolic 2*log(2)
L = LazyDirichletSeriesRing(ZZ, "z") mu = L(moebius); mu.valuation() # needs sage.libs.pari (mu - mu).valuation() # needs sage.libs.pari g = L(constant=1, valuation=2) g.valuation() # needs sage.symbolic (g*g).valuation() # needs sage.symbolic
- class sage.rings.lazy_series.LazyLaurentSeries(parent, coeff_stream)[source]¶
Bases:
LazyCauchyProductSeriesA Laurent series where the coefficients are computed lazily.
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1)
L.<z> = LazyLaurentSeriesRing(ZZ)
We can build a series from a function and specify if the series eventually takes a constant value:
sage: f = L(lambda i: i, valuation=-3, constant=-1, degree=3) sage: f -3*z^-3 - 2*z^-2 - z^-1 + z + 2*z^2 - z^3 - z^4 - z^5 + O(z^6) sage: f[-2] -2 sage: f[10] -1 sage: f[-5] 0 sage: f = L(lambda i: i, valuation=-3) sage: f -3*z^-3 - 2*z^-2 - z^-1 + z + 2*z^2 + 3*z^3 + O(z^4) sage: f[20] 20
>>> from sage.all import * >>> f = L(lambda i: i, valuation=-Integer(3), constant=-Integer(1), degree=Integer(3)) >>> f -3*z^-3 - 2*z^-2 - z^-1 + z + 2*z^2 - z^3 - z^4 - z^5 + O(z^6) >>> f[-Integer(2)] -2 >>> f[Integer(10)] -1 >>> f[-Integer(5)] 0 >>> f = L(lambda i: i, valuation=-Integer(3)) >>> f -3*z^-3 - 2*z^-2 - z^-1 + z + 2*z^2 + 3*z^3 + O(z^4) >>> f[Integer(20)] 20
f = L(lambda i: i, valuation=-3, constant=-1, degree=3) f f[-2] f[10] f[-5] f = L(lambda i: i, valuation=-3) f f[20]
Anything that converts into a polynomial can be input, where we can also specify the valuation or if the series eventually takes a constant value:
sage: L([-5,2,0,5]) -5 + 2*z + 5*z^3 sage: L([-5,2,0,5], constant=6) -5 + 2*z + 5*z^3 + 6*z^4 + 6*z^5 + 6*z^6 + O(z^7) sage: L([-5,2,0,5], degree=6, constant=6) -5 + 2*z + 5*z^3 + 6*z^6 + 6*z^7 + 6*z^8 + O(z^9) sage: L([-5,2,0,5], valuation=-2, degree=3, constant=6) -5*z^-2 + 2*z^-1 + 5*z + 6*z^3 + 6*z^4 + 6*z^5 + O(z^6) sage: L([-5,2,0,5], valuation=5) -5*z^5 + 2*z^6 + 5*z^8 sage: L({-2:9, 3:4}, constant=2, degree=5) 9*z^-2 + 4*z^3 + 2*z^5 + 2*z^6 + 2*z^7 + O(z^8)
>>> from sage.all import * >>> L([-Integer(5),Integer(2),Integer(0),Integer(5)]) -5 + 2*z + 5*z^3 >>> L([-Integer(5),Integer(2),Integer(0),Integer(5)], constant=Integer(6)) -5 + 2*z + 5*z^3 + 6*z^4 + 6*z^5 + 6*z^6 + O(z^7) >>> L([-Integer(5),Integer(2),Integer(0),Integer(5)], degree=Integer(6), constant=Integer(6)) -5 + 2*z + 5*z^3 + 6*z^6 + 6*z^7 + 6*z^8 + O(z^9) >>> L([-Integer(5),Integer(2),Integer(0),Integer(5)], valuation=-Integer(2), degree=Integer(3), constant=Integer(6)) -5*z^-2 + 2*z^-1 + 5*z + 6*z^3 + 6*z^4 + 6*z^5 + O(z^6) >>> L([-Integer(5),Integer(2),Integer(0),Integer(5)], valuation=Integer(5)) -5*z^5 + 2*z^6 + 5*z^8 >>> L({-Integer(2):Integer(9), Integer(3):Integer(4)}, constant=Integer(2), degree=Integer(5)) 9*z^-2 + 4*z^3 + 2*z^5 + 2*z^6 + 2*z^7 + O(z^8)
L([-5,2,0,5]) L([-5,2,0,5], constant=6) L([-5,2,0,5], degree=6, constant=6) L([-5,2,0,5], valuation=-2, degree=3, constant=6) L([-5,2,0,5], valuation=5) L({-2:9, 3:4}, constant=2, degree=5)We can also perform arithmetic:
sage: f = 1 / (1 - z - z^2) sage: f 1 + z + 2*z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7) sage: f.coefficient(100) 573147844013817084101 sage: f = (z^-2 - 1 + 2*z) / (z^-1 - z + 3*z^2) sage: f z^-1 - z^2 - z^4 + 3*z^5 + O(z^6)
>>> from sage.all import * >>> f = Integer(1) / (Integer(1) - z - z**Integer(2)) >>> f 1 + z + 2*z^2 + 3*z^3 + 5*z^4 + 8*z^5 + 13*z^6 + O(z^7) >>> f.coefficient(Integer(100)) 573147844013817084101 >>> f = (z**-Integer(2) - Integer(1) + Integer(2)*z) / (z**-Integer(1) - z + Integer(3)*z**Integer(2)) >>> f z^-1 - z^2 - z^4 + 3*z^5 + O(z^6)
f = 1 / (1 - z - z^2) f f.coefficient(100) f = (z^-2 - 1 + 2*z) / (z^-1 - z + 3*z^2) f
However, we may not always be able to know when a result is exactly a polynomial:
sage: f * (z^-1 - z + 3*z^2) z^-2 - 1 + 2*z + O(z^5)
>>> from sage.all import * >>> f * (z**-Integer(1) - z + Integer(3)*z**Integer(2)) z^-2 - 1 + 2*z + O(z^5)
f * (z^-1 - z + 3*z^2)
- O(prec, name=None)[source]¶
Return the Laurent series with absolute precision
precapproximated from this series.INPUT:
prec– integername– name of the variable; if it isNone, the name of the variable of the series is used
OUTPUT: a Laurent series with absolute precision
precEXAMPLES:
sage: L = LazyLaurentSeriesRing(ZZ, 'z') sage: z = L.gen() sage: f = (z - 2*z^3)^5/(1 - 2*z) sage: f z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + 32*z^10 - 16*z^11 + O(z^12) sage: g = f.approximate_series(10) sage: g z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + O(z^10) sage: g.parent() Power Series Ring in z over Integer Ring sage: h = (f^-1).approximate_series(3) sage: h z^-5 - 2*z^-4 + 10*z^-3 - 20*z^-2 + 60*z^-1 - 120 + 280*z - 560*z^2 + O(z^3) sage: h.parent() Laurent Series Ring in z over Integer Ring
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, 'z') >>> z = L.gen() >>> f = (z - Integer(2)*z**Integer(3))**Integer(5)/(Integer(1) - Integer(2)*z) >>> f z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + 32*z^10 - 16*z^11 + O(z^12) >>> g = f.approximate_series(Integer(10)) >>> g z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + O(z^10) >>> g.parent() Power Series Ring in z over Integer Ring >>> h = (f**-Integer(1)).approximate_series(Integer(3)) >>> h z^-5 - 2*z^-4 + 10*z^-3 - 20*z^-2 + 60*z^-1 - 120 + 280*z - 560*z^2 + O(z^3) >>> h.parent() Laurent Series Ring in z over Integer Ring
L = LazyLaurentSeriesRing(ZZ, 'z') z = L.gen() f = (z - 2*z^3)^5/(1 - 2*z) f g = f.approximate_series(10) g g.parent() h = (f^-1).approximate_series(3) h h.parent()
- add_bigoh(prec, name=None)[source]¶
Return the Laurent series with absolute precision
precapproximated from this series.INPUT:
prec– integername– name of the variable; if it isNone, the name of the variable of the series is used
OUTPUT: a Laurent series with absolute precision
precEXAMPLES:
sage: L = LazyLaurentSeriesRing(ZZ, 'z') sage: z = L.gen() sage: f = (z - 2*z^3)^5/(1 - 2*z) sage: f z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + 32*z^10 - 16*z^11 + O(z^12) sage: g = f.approximate_series(10) sage: g z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + O(z^10) sage: g.parent() Power Series Ring in z over Integer Ring sage: h = (f^-1).approximate_series(3) sage: h z^-5 - 2*z^-4 + 10*z^-3 - 20*z^-2 + 60*z^-1 - 120 + 280*z - 560*z^2 + O(z^3) sage: h.parent() Laurent Series Ring in z over Integer Ring
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, 'z') >>> z = L.gen() >>> f = (z - Integer(2)*z**Integer(3))**Integer(5)/(Integer(1) - Integer(2)*z) >>> f z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + 32*z^10 - 16*z^11 + O(z^12) >>> g = f.approximate_series(Integer(10)) >>> g z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + O(z^10) >>> g.parent() Power Series Ring in z over Integer Ring >>> h = (f**-Integer(1)).approximate_series(Integer(3)) >>> h z^-5 - 2*z^-4 + 10*z^-3 - 20*z^-2 + 60*z^-1 - 120 + 280*z - 560*z^2 + O(z^3) >>> h.parent() Laurent Series Ring in z over Integer Ring
L = LazyLaurentSeriesRing(ZZ, 'z') z = L.gen() f = (z - 2*z^3)^5/(1 - 2*z) f g = f.approximate_series(10) g g.parent() h = (f^-1).approximate_series(3) h h.parent()
- approximate_series(prec, name=None)[source]¶
Return the Laurent series with absolute precision
precapproximated from this series.INPUT:
prec– integername– name of the variable; if it isNone, the name of the variable of the series is used
OUTPUT: a Laurent series with absolute precision
precEXAMPLES:
sage: L = LazyLaurentSeriesRing(ZZ, 'z') sage: z = L.gen() sage: f = (z - 2*z^3)^5/(1 - 2*z) sage: f z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + 32*z^10 - 16*z^11 + O(z^12) sage: g = f.approximate_series(10) sage: g z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + O(z^10) sage: g.parent() Power Series Ring in z over Integer Ring sage: h = (f^-1).approximate_series(3) sage: h z^-5 - 2*z^-4 + 10*z^-3 - 20*z^-2 + 60*z^-1 - 120 + 280*z - 560*z^2 + O(z^3) sage: h.parent() Laurent Series Ring in z over Integer Ring
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, 'z') >>> z = L.gen() >>> f = (z - Integer(2)*z**Integer(3))**Integer(5)/(Integer(1) - Integer(2)*z) >>> f z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + 32*z^10 - 16*z^11 + O(z^12) >>> g = f.approximate_series(Integer(10)) >>> g z^5 + 2*z^6 - 6*z^7 - 12*z^8 + 16*z^9 + O(z^10) >>> g.parent() Power Series Ring in z over Integer Ring >>> h = (f**-Integer(1)).approximate_series(Integer(3)) >>> h z^-5 - 2*z^-4 + 10*z^-3 - 20*z^-2 + 60*z^-1 - 120 + 280*z - 560*z^2 + O(z^3) >>> h.parent() Laurent Series Ring in z over Integer Ring
L = LazyLaurentSeriesRing(ZZ, 'z') z = L.gen() f = (z - 2*z^3)^5/(1 - 2*z) f g = f.approximate_series(10) g g.parent() h = (f^-1).approximate_series(3) h h.parent()
- compose(g)[source]¶
Return the composition of
selfwithg.Given two Laurent series \(f\) and \(g\) over the same base ring, the composition \((f \circ g)(z) = f(g(z))\) is defined if and only if:
\(g = 0\) and \(\mathrm{val}(f) \geq 0\),
\(g\) is nonzero and \(f\) has only finitely many nonzero coefficients,
\(g\) is nonzero and \(\mathrm{val}(g) > 0\).
INPUT:
g– other series
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: f = z^2 + 1 + z sage: f(0) 1 sage: f(L(0)) 1 sage: f(f) 3 + 3*z + 4*z^2 + 2*z^3 + z^4 sage: g = z^-3/(1-2*z); g z^-3 + 2*z^-2 + 4*z^-1 + 8 + 16*z + 32*z^2 + 64*z^3 + O(z^4) sage: f(g) z^-6 + 4*z^-5 + 12*z^-4 + 33*z^-3 + 82*z^-2 + 196*z^-1 + 457 + O(z) sage: g^2 + 1 + g z^-6 + 4*z^-5 + 12*z^-4 + 33*z^-3 + 82*z^-2 + 196*z^-1 + 457 + O(z) sage: f(int(2)) 7 sage: f = z^-2 + z + 4*z^3 sage: f(f) 4*z^-6 + 12*z^-3 + z^-2 + 48*z^-1 + 12 + O(z) sage: f^-2 + f + 4*f^3 4*z^-6 + 12*z^-3 + z^-2 + 48*z^-1 + 12 + O(z) sage: f(g) 4*z^-9 + 24*z^-8 + 96*z^-7 + 320*z^-6 + 960*z^-5 + 2688*z^-4 + 7169*z^-3 + O(z^-2) sage: g^-2 + g + 4*g^3 4*z^-9 + 24*z^-8 + 96*z^-7 + 320*z^-6 + 960*z^-5 + 2688*z^-4 + 7169*z^-3 + O(z^-2) sage: f = z^-3 + z^-2 + 1 / (1 + z^2); f z^-3 + z^-2 + 1 - z^2 + O(z^4) sage: g = z^3 / (1 + z - z^3); g z^3 - z^4 + z^5 - z^7 + 2*z^8 - 2*z^9 + O(z^10) sage: f(g) z^-9 + 3*z^-8 + 3*z^-7 - z^-6 - 4*z^-5 - 2*z^-4 + z^-3 + O(z^-2) sage: g^-3 + g^-2 + 1 / (1 + g^2) z^-9 + 3*z^-8 + 3*z^-7 - z^-6 - 4*z^-5 - 2*z^-4 + z^-3 + O(z^-2) sage: f = z^-3 sage: g = z^-2 + z^-1 sage: g^(-3) z^6 - 3*z^7 + 6*z^8 - 10*z^9 + 15*z^10 - 21*z^11 + 28*z^12 + O(z^13) sage: f(g) z^6 - 3*z^7 + 6*z^8 - 10*z^9 + 15*z^10 - 21*z^11 + 28*z^12 + O(z^13) sage: f = z^2 + z^3 sage: g = z^-3 + z^-2 sage: f^-3 + f^-2 z^-6 - 3*z^-5 + 7*z^-4 - 12*z^-3 + 18*z^-2 - 25*z^-1 + 33 + O(z) sage: g(f) z^-6 - 3*z^-5 + 7*z^-4 - 12*z^-3 + 18*z^-2 - 25*z^-1 + 33 + O(z) sage: g^2 + g^3 z^-9 + 3*z^-8 + 3*z^-7 + 2*z^-6 + 2*z^-5 + z^-4 sage: f(g) z^-9 + 3*z^-8 + 3*z^-7 + 2*z^-6 + 2*z^-5 + z^-4 sage: f = L(lambda n: n, valuation=0); f z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) sage: f(z^2) z^2 + 2*z^4 + 3*z^6 + 4*z^8 + O(z^9) sage: f = L(lambda n: n, valuation=-2); f -2*z^-2 - z^-1 + z + 2*z^2 + 3*z^3 + 4*z^4 + O(z^5) sage: f3 = f(z^3); f3 -2*z^-6 - z^-3 + O(z) sage: [f3[i] for i in range(-6,13)] [-2, 0, 0, -1, 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 0, 3, 0, 0, 4]
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> f = z**Integer(2) + Integer(1) + z >>> f(Integer(0)) 1 >>> f(L(Integer(0))) 1 >>> f(f) 3 + 3*z + 4*z^2 + 2*z^3 + z^4 >>> g = z**-Integer(3)/(Integer(1)-Integer(2)*z); g z^-3 + 2*z^-2 + 4*z^-1 + 8 + 16*z + 32*z^2 + 64*z^3 + O(z^4) >>> f(g) z^-6 + 4*z^-5 + 12*z^-4 + 33*z^-3 + 82*z^-2 + 196*z^-1 + 457 + O(z) >>> g**Integer(2) + Integer(1) + g z^-6 + 4*z^-5 + 12*z^-4 + 33*z^-3 + 82*z^-2 + 196*z^-1 + 457 + O(z) >>> f(int(Integer(2))) 7 >>> f = z**-Integer(2) + z + Integer(4)*z**Integer(3) >>> f(f) 4*z^-6 + 12*z^-3 + z^-2 + 48*z^-1 + 12 + O(z) >>> f**-Integer(2) + f + Integer(4)*f**Integer(3) 4*z^-6 + 12*z^-3 + z^-2 + 48*z^-1 + 12 + O(z) >>> f(g) 4*z^-9 + 24*z^-8 + 96*z^-7 + 320*z^-6 + 960*z^-5 + 2688*z^-4 + 7169*z^-3 + O(z^-2) >>> g**-Integer(2) + g + Integer(4)*g**Integer(3) 4*z^-9 + 24*z^-8 + 96*z^-7 + 320*z^-6 + 960*z^-5 + 2688*z^-4 + 7169*z^-3 + O(z^-2) >>> f = z**-Integer(3) + z**-Integer(2) + Integer(1) / (Integer(1) + z**Integer(2)); f z^-3 + z^-2 + 1 - z^2 + O(z^4) >>> g = z**Integer(3) / (Integer(1) + z - z**Integer(3)); g z^3 - z^4 + z^5 - z^7 + 2*z^8 - 2*z^9 + O(z^10) >>> f(g) z^-9 + 3*z^-8 + 3*z^-7 - z^-6 - 4*z^-5 - 2*z^-4 + z^-3 + O(z^-2) >>> g**-Integer(3) + g**-Integer(2) + Integer(1) / (Integer(1) + g**Integer(2)) z^-9 + 3*z^-8 + 3*z^-7 - z^-6 - 4*z^-5 - 2*z^-4 + z^-3 + O(z^-2) >>> f = z**-Integer(3) >>> g = z**-Integer(2) + z**-Integer(1) >>> g**(-Integer(3)) z^6 - 3*z^7 + 6*z^8 - 10*z^9 + 15*z^10 - 21*z^11 + 28*z^12 + O(z^13) >>> f(g) z^6 - 3*z^7 + 6*z^8 - 10*z^9 + 15*z^10 - 21*z^11 + 28*z^12 + O(z^13) >>> f = z**Integer(2) + z**Integer(3) >>> g = z**-Integer(3) + z**-Integer(2) >>> f**-Integer(3) + f**-Integer(2) z^-6 - 3*z^-5 + 7*z^-4 - 12*z^-3 + 18*z^-2 - 25*z^-1 + 33 + O(z) >>> g(f) z^-6 - 3*z^-5 + 7*z^-4 - 12*z^-3 + 18*z^-2 - 25*z^-1 + 33 + O(z) >>> g**Integer(2) + g**Integer(3) z^-9 + 3*z^-8 + 3*z^-7 + 2*z^-6 + 2*z^-5 + z^-4 >>> f(g) z^-9 + 3*z^-8 + 3*z^-7 + 2*z^-6 + 2*z^-5 + z^-4 >>> f = L(lambda n: n, valuation=Integer(0)); f z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) >>> f(z**Integer(2)) z^2 + 2*z^4 + 3*z^6 + 4*z^8 + O(z^9) >>> f = L(lambda n: n, valuation=-Integer(2)); f -2*z^-2 - z^-1 + z + 2*z^2 + 3*z^3 + 4*z^4 + O(z^5) >>> f3 = f(z**Integer(3)); f3 -2*z^-6 - z^-3 + O(z) >>> [f3[i] for i in range(-Integer(6),Integer(13))] [-2, 0, 0, -1, 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 0, 3, 0, 0, 4]
L.<z> = LazyLaurentSeriesRing(QQ) f = z^2 + 1 + z f(0) f(L(0)) f(f) g = z^-3/(1-2*z); g f(g) g^2 + 1 + g f(int(2)) f = z^-2 + z + 4*z^3 f(f) f^-2 + f + 4*f^3 f(g) g^-2 + g + 4*g^3 f = z^-3 + z^-2 + 1 / (1 + z^2); f g = z^3 / (1 + z - z^3); g f(g) g^-3 + g^-2 + 1 / (1 + g^2) f = z^-3 g = z^-2 + z^-1 g^(-3) f(g) f = z^2 + z^3 g = z^-3 + z^-2 f^-3 + f^-2 g(f) g^2 + g^3 f(g) f = L(lambda n: n, valuation=0); f f(z^2) f = L(lambda n: n, valuation=-2); f f3 = f(z^3); f3 [f3[i] for i in range(-6,13)]
We compose a Laurent polynomial with a generic element:
sage: R.<x> = QQ[] sage: f = z^2 + 1 + z^-1 sage: g = x^2 + x + 3 sage: f(g) (x^6 + 3*x^5 + 12*x^4 + 19*x^3 + 37*x^2 + 28*x + 31)/(x^2 + x + 3) sage: f(g) == g^2 + 1 + g^-1 True
>>> from sage.all import * >>> R = QQ['x']; (x,) = R._first_ngens(1) >>> f = z**Integer(2) + Integer(1) + z**-Integer(1) >>> g = x**Integer(2) + x + Integer(3) >>> f(g) (x^6 + 3*x^5 + 12*x^4 + 19*x^3 + 37*x^2 + 28*x + 31)/(x^2 + x + 3) >>> f(g) == g**Integer(2) + Integer(1) + g**-Integer(1) True
R.<x> = QQ[] f = z^2 + 1 + z^-1 g = x^2 + x + 3 f(g) f(g) == g^2 + 1 + g^-1
We compose with another lazy Laurent series:
sage: LS.<y> = LazyLaurentSeriesRing(QQ) sage: f = z^2 + 1 + z^-1 sage: fy = f(y); fy y^-1 + 1 + y^2 sage: fy.parent() is LS True sage: g = y - y sage: f(g) Traceback (most recent call last): ... ZeroDivisionError: the valuation of the series must be nonnegative sage: g = 1 - y sage: f(g) 3 - y + 2*y^2 + y^3 + y^4 + y^5 + O(y^6) sage: g^2 + 1 + g^-1 3 - y + 2*y^2 + y^3 + y^4 + y^5 + O(y^6) sage: f = L(lambda n: n, valuation=0); f z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) sage: f(0) 0 sage: f(y) y + 2*y^2 + 3*y^3 + 4*y^4 + 5*y^5 + 6*y^6 + 7*y^7 + O(y^8) sage: fp = f(y - y) sage: fp == 0 True sage: fp.parent() is LS True sage: f = z^2 + 3 + z sage: f(y - y) 3
>>> from sage.all import * >>> LS = LazyLaurentSeriesRing(QQ, names=('y',)); (y,) = LS._first_ngens(1) >>> f = z**Integer(2) + Integer(1) + z**-Integer(1) >>> fy = f(y); fy y^-1 + 1 + y^2 >>> fy.parent() is LS True >>> g = y - y >>> f(g) Traceback (most recent call last): ... ZeroDivisionError: the valuation of the series must be nonnegative >>> g = Integer(1) - y >>> f(g) 3 - y + 2*y^2 + y^3 + y^4 + y^5 + O(y^6) >>> g**Integer(2) + Integer(1) + g**-Integer(1) 3 - y + 2*y^2 + y^3 + y^4 + y^5 + O(y^6) >>> f = L(lambda n: n, valuation=Integer(0)); f z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) >>> f(Integer(0)) 0 >>> f(y) y + 2*y^2 + 3*y^3 + 4*y^4 + 5*y^5 + 6*y^6 + 7*y^7 + O(y^8) >>> fp = f(y - y) >>> fp == Integer(0) True >>> fp.parent() is LS True >>> f = z**Integer(2) + Integer(3) + z >>> f(y - y) 3
LS.<y> = LazyLaurentSeriesRing(QQ) f = z^2 + 1 + z^-1 fy = f(y); fy fy.parent() is LS g = y - y f(g) g = 1 - y f(g) g^2 + 1 + g^-1 f = L(lambda n: n, valuation=0); f f(0) f(y) fp = f(y - y) fp == 0 fp.parent() is LS f = z^2 + 3 + z f(y - y)
With both of them sparse:
sage: L.<z> = LazyLaurentSeriesRing(QQ, sparse=True) sage: LS.<y> = LazyLaurentSeriesRing(QQ, sparse=True) sage: f = L(lambda n: 1, valuation=0); f 1 + z + z^2 + z^3 + z^4 + z^5 + z^6 + O(z^7) sage: f(y^2) 1 + y^2 + y^4 + y^6 + O(y^7) sage: fp = f - 1 + z^-2; fp z^-2 + z + z^2 + z^3 + z^4 + O(z^5) sage: fpy = fp(y^2); fpy y^-4 + y^2 + O(y^3) sage: fpy.parent() is LS True sage: [fpy[i] for i in range(-4,11)] [1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1] sage: g = LS(valuation=2, constant=1); g y^2 + y^3 + y^4 + O(y^5) sage: fg = f(g); fg 1 + y^2 + y^3 + 2*y^4 + 3*y^5 + 5*y^6 + O(y^7) sage: 1 + g + g^2 + g^3 + g^4 + g^5 + g^6 1 + y^2 + y^3 + 2*y^4 + 3*y^5 + 5*y^6 + O(y^7) sage: h = LS(lambda n: 1 if n % 2 else 0, valuation=2); h y^3 + y^5 + y^7 + O(y^9) sage: fgh = fg(h); fgh 1 + y^6 + O(y^7) sage: [fgh[i] for i in range(0, 15)] [1, 0, 0, 0, 0, 0, 1, 0, 2, 1, 3, 3, 6, 6, 13] sage: t = 1 + h^2 + h^3 + 2*h^4 + 3*h^5 + 5*h^6 sage: [t[i] for i in range(0, 15)] [1, 0, 0, 0, 0, 0, 1, 0, 2, 1, 3, 3, 6, 6, 13]
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, sparse=True, names=('z',)); (z,) = L._first_ngens(1) >>> LS = LazyLaurentSeriesRing(QQ, sparse=True, names=('y',)); (y,) = LS._first_ngens(1) >>> f = L(lambda n: Integer(1), valuation=Integer(0)); f 1 + z + z^2 + z^3 + z^4 + z^5 + z^6 + O(z^7) >>> f(y**Integer(2)) 1 + y^2 + y^4 + y^6 + O(y^7) >>> fp = f - Integer(1) + z**-Integer(2); fp z^-2 + z + z^2 + z^3 + z^4 + O(z^5) >>> fpy = fp(y**Integer(2)); fpy y^-4 + y^2 + O(y^3) >>> fpy.parent() is LS True >>> [fpy[i] for i in range(-Integer(4),Integer(11))] [1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1] >>> g = LS(valuation=Integer(2), constant=Integer(1)); g y^2 + y^3 + y^4 + O(y^5) >>> fg = f(g); fg 1 + y^2 + y^3 + 2*y^4 + 3*y^5 + 5*y^6 + O(y^7) >>> Integer(1) + g + g**Integer(2) + g**Integer(3) + g**Integer(4) + g**Integer(5) + g**Integer(6) 1 + y^2 + y^3 + 2*y^4 + 3*y^5 + 5*y^6 + O(y^7) >>> h = LS(lambda n: Integer(1) if n % Integer(2) else Integer(0), valuation=Integer(2)); h y^3 + y^5 + y^7 + O(y^9) >>> fgh = fg(h); fgh 1 + y^6 + O(y^7) >>> [fgh[i] for i in range(Integer(0), Integer(15))] [1, 0, 0, 0, 0, 0, 1, 0, 2, 1, 3, 3, 6, 6, 13] >>> t = Integer(1) + h**Integer(2) + h**Integer(3) + Integer(2)*h**Integer(4) + Integer(3)*h**Integer(5) + Integer(5)*h**Integer(6) >>> [t[i] for i in range(Integer(0), Integer(15))] [1, 0, 0, 0, 0, 0, 1, 0, 2, 1, 3, 3, 6, 6, 13]
L.<z> = LazyLaurentSeriesRing(QQ, sparse=True) LS.<y> = LazyLaurentSeriesRing(QQ, sparse=True) f = L(lambda n: 1, valuation=0); f f(y^2) fp = f - 1 + z^-2; fp fpy = fp(y^2); fpy fpy.parent() is LS [fpy[i] for i in range(-4,11)] g = LS(valuation=2, constant=1); g fg = f(g); fg 1 + g + g^2 + g^3 + g^4 + g^5 + g^6 h = LS(lambda n: 1 if n % 2 else 0, valuation=2); h fgh = fg(h); fgh [fgh[i] for i in range(0, 15)] t = 1 + h^2 + h^3 + 2*h^4 + 3*h^5 + 5*h^6 [t[i] for i in range(0, 15)]
We look at mixing the sparse and the dense:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: f = L(lambda n: 1, valuation=0); f 1 + z + z^2 + z^3 + z^4 + z^5 + z^6 + O(z^7) sage: g = LS(lambda n: 1, valuation=1); g y + y^2 + y^3 + y^4 + y^5 + y^6 + y^7 + O(y^8) sage: f(g) 1 + y + 2*y^2 + 4*y^3 + 8*y^4 + 16*y^5 + 32*y^6 + O(y^7) sage: f = z^-2 + 1 + z sage: g = 1/(y*(1-y)); g y^-1 + 1 + y + O(y^2) sage: f(g) y^-1 + 2 + y + 2*y^2 - y^3 + 2*y^4 + y^5 + y^6 + y^7 + O(y^8) sage: g^-2 + 1 + g == f(g) True sage: f = z^-3 + z^-2 + 1 sage: g = 1/(y^2*(1-y)); g y^-2 + y^-1 + 1 + O(y) sage: f(g) 1 + y^4 - 2*y^5 + 2*y^6 - 3*y^7 + 3*y^8 - y^9 sage: g^-3 + g^-2 + 1 == f(g) True sage: z(y) y
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> f = L(lambda n: Integer(1), valuation=Integer(0)); f 1 + z + z^2 + z^3 + z^4 + z^5 + z^6 + O(z^7) >>> g = LS(lambda n: Integer(1), valuation=Integer(1)); g y + y^2 + y^3 + y^4 + y^5 + y^6 + y^7 + O(y^8) >>> f(g) 1 + y + 2*y^2 + 4*y^3 + 8*y^4 + 16*y^5 + 32*y^6 + O(y^7) >>> f = z**-Integer(2) + Integer(1) + z >>> g = Integer(1)/(y*(Integer(1)-y)); g y^-1 + 1 + y + O(y^2) >>> f(g) y^-1 + 2 + y + 2*y^2 - y^3 + 2*y^4 + y^5 + y^6 + y^7 + O(y^8) >>> g**-Integer(2) + Integer(1) + g == f(g) True >>> f = z**-Integer(3) + z**-Integer(2) + Integer(1) >>> g = Integer(1)/(y**Integer(2)*(Integer(1)-y)); g y^-2 + y^-1 + 1 + O(y) >>> f(g) 1 + y^4 - 2*y^5 + 2*y^6 - 3*y^7 + 3*y^8 - y^9 >>> g**-Integer(3) + g**-Integer(2) + Integer(1) == f(g) True >>> z(y) y
L.<z> = LazyLaurentSeriesRing(QQ) f = L(lambda n: 1, valuation=0); f g = LS(lambda n: 1, valuation=1); g f(g) f = z^-2 + 1 + z g = 1/(y*(1-y)); g f(g) g^-2 + 1 + g == f(g) f = z^-3 + z^-2 + 1 g = 1/(y^2*(1-y)); g f(g) g^-3 + g^-2 + 1 == f(g) z(y)
We look at cases where the composition does not exist. \(g = 0\) and \(\mathrm{val}(f) < 0\):
sage: g = L(0) sage: f = z^-1 + z^-2 sage: f.valuation() < 0 True sage: f(g) Traceback (most recent call last): ... ZeroDivisionError: the valuation of the series must be nonnegative
>>> from sage.all import * >>> g = L(Integer(0)) >>> f = z**-Integer(1) + z**-Integer(2) >>> f.valuation() < Integer(0) True >>> f(g) Traceback (most recent call last): ... ZeroDivisionError: the valuation of the series must be nonnegative
g = L(0) f = z^-1 + z^-2 f.valuation() < 0 f(g)
\(g \neq 0\) and \(\mathrm{val}(g) \leq 0\) and \(f\) has infinitely many nonzero coefficients:
sage: g = z^-1 + z^-2 sage: g.valuation() <= 0 True sage: f = L(lambda n: n, valuation=0) sage: f(g) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series sage: f = L(lambda n: n, valuation=1) sage: f(1 + z) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series
>>> from sage.all import * >>> g = z**-Integer(1) + z**-Integer(2) >>> g.valuation() <= Integer(0) True >>> f = L(lambda n: n, valuation=Integer(0)) >>> f(g) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series >>> f = L(lambda n: n, valuation=Integer(1)) >>> f(Integer(1) + z) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series
g = z^-1 + z^-2 g.valuation() <= 0 f = L(lambda n: n, valuation=0) f(g) f = L(lambda n: n, valuation=1) f(1 + z)
We compose the exponential with a Dirichlet series:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: e = L(lambda n: 1/factorial(n), 0) sage: D = LazyDirichletSeriesRing(QQ, "s") sage: g = D(constant=1)-1 sage: g # needs sage.symbolic 1/(2^s) + 1/(3^s) + 1/(4^s) + O(1/(5^s)) sage: e(g)[0:10] [0, 1, 1, 1, 3/2, 1, 2, 1, 13/6, 3/2] sage: sum(g^k/factorial(k) for k in range(10))[0:10] [0, 1, 1, 1, 3/2, 1, 2, 1, 13/6, 3/2] sage: g = D([0,1,0,1,1,2]) sage: g # needs sage.symbolic 1/(2^s) + 1/(4^s) + 1/(5^s) + 2/6^s sage: e(g)[0:10] [0, 1, 1, 0, 3/2, 1, 2, 0, 7/6, 0] sage: sum(g^k/factorial(k) for k in range(10))[0:10] [0, 1, 1, 0, 3/2, 1, 2, 0, 7/6, 0] sage: e(D([1,0,1])) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series sage: e5 = L(e, degree=5) sage: e5 1 + z + 1/2*z^2 + 1/6*z^3 + 1/24*z^4 sage: e5(g) # needs sage.symbolic 1 + 1/(2^s) + 3/2/4^s + 1/(5^s) + 2/6^s + O(1/(8^s)) sage: sum(e5[k] * g^k for k in range(5)) # needs sage.symbolic 1 + 1/(2^s) + 3/2/4^s + 1/(5^s) + 2/6^s + O(1/(8^s))
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> e = L(lambda n: Integer(1)/factorial(n), Integer(0)) >>> D = LazyDirichletSeriesRing(QQ, "s") >>> g = D(constant=Integer(1))-Integer(1) >>> g # needs sage.symbolic 1/(2^s) + 1/(3^s) + 1/(4^s) + O(1/(5^s)) >>> e(g)[Integer(0):Integer(10)] [0, 1, 1, 1, 3/2, 1, 2, 1, 13/6, 3/2] >>> sum(g**k/factorial(k) for k in range(Integer(10)))[Integer(0):Integer(10)] [0, 1, 1, 1, 3/2, 1, 2, 1, 13/6, 3/2] >>> g = D([Integer(0),Integer(1),Integer(0),Integer(1),Integer(1),Integer(2)]) >>> g # needs sage.symbolic 1/(2^s) + 1/(4^s) + 1/(5^s) + 2/6^s >>> e(g)[Integer(0):Integer(10)] [0, 1, 1, 0, 3/2, 1, 2, 0, 7/6, 0] >>> sum(g**k/factorial(k) for k in range(Integer(10)))[Integer(0):Integer(10)] [0, 1, 1, 0, 3/2, 1, 2, 0, 7/6, 0] >>> e(D([Integer(1),Integer(0),Integer(1)])) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series >>> e5 = L(e, degree=Integer(5)) >>> e5 1 + z + 1/2*z^2 + 1/6*z^3 + 1/24*z^4 >>> e5(g) # needs sage.symbolic 1 + 1/(2^s) + 3/2/4^s + 1/(5^s) + 2/6^s + O(1/(8^s)) >>> sum(e5[k] * g**k for k in range(Integer(5))) # needs sage.symbolic 1 + 1/(2^s) + 3/2/4^s + 1/(5^s) + 2/6^s + O(1/(8^s))
L.<z> = LazyLaurentSeriesRing(QQ) e = L(lambda n: 1/factorial(n), 0) D = LazyDirichletSeriesRing(QQ, "s") g = D(constant=1)-1 g # needs sage.symbolic e(g)[0:10] sum(g^k/factorial(k) for k in range(10))[0:10] g = D([0,1,0,1,1,2]) g # needs sage.symbolic e(g)[0:10] sum(g^k/factorial(k) for k in range(10))[0:10] e(D([1,0,1])) e5 = L(e, degree=5) e5 e5(g) # needs sage.symbolic sum(e5[k] * g^k for k in range(5)) # needs sage.symbolic
The output parent is always the common parent between the base ring of \(f\) and the parent of \(g\) or extended to the corresponding lazy series:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: R.<x> = ZZ[] sage: parent(z(x)) Univariate Polynomial Ring in x over Rational Field sage: parent(z(R.zero())) Univariate Polynomial Ring in x over Rational Field sage: parent(z(0)) Rational Field sage: f = 1 / (1 - z) sage: f(x) 1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + O(x^7) sage: three = L(3)(x^2); three 3 sage: parent(three) Univariate Polynomial Ring in x over Rational Field
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> R = ZZ['x']; (x,) = R._first_ngens(1) >>> parent(z(x)) Univariate Polynomial Ring in x over Rational Field >>> parent(z(R.zero())) Univariate Polynomial Ring in x over Rational Field >>> parent(z(Integer(0))) Rational Field >>> f = Integer(1) / (Integer(1) - z) >>> f(x) 1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + O(x^7) >>> three = L(Integer(3))(x**Integer(2)); three 3 >>> parent(three) Univariate Polynomial Ring in x over Rational Field
L.<z> = LazyLaurentSeriesRing(QQ) R.<x> = ZZ[] parent(z(x)) parent(z(R.zero())) parent(z(0)) f = 1 / (1 - z) f(x) three = L(3)(x^2); three parent(three)
Consistency check when \(g\) is an uninitialized series between a polynomial \(f\) as both a polynomial and a lazy series:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: f = 1 + z sage: g = L.undefined(valuation=0) sage: f(g) == f.polynomial()(g) True
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> f = Integer(1) + z >>> g = L.undefined(valuation=Integer(0)) >>> f(g) == f.polynomial()(g) True
L.<z> = LazyLaurentSeriesRing(QQ) f = 1 + z g = L.undefined(valuation=0) f(g) == f.polynomial()(g)
- compositional_inverse()[source]¶
Return the compositional inverse of
self.Given a Laurent series \(f\), the compositional inverse is a Laurent series \(g\) over the same base ring, such that \((f \circ g)(z) = f(g(z)) = z\).
The compositional inverse exists if and only if:
\(\mathrm{val}(f) = 1\), or
\(f = a + b z\) with \(a, b \neq 0\), or
\(f = a/z\) with \(a \neq 0\).
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: (2*z).revert() 1/2*z sage: (2/z).revert() 2*z^-1 sage: (z-z^2).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) sage: s = L(degree=1, constant=-1) sage: s.revert() -z - z^2 - z^3 + O(z^4) sage: s = L(degree=1, constant=1) sage: s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> (Integer(2)*z).revert() 1/2*z >>> (Integer(2)/z).revert() 2*z^-1 >>> (z-z**Integer(2)).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) >>> s = L(degree=Integer(1), constant=-Integer(1)) >>> s.revert() -z - z^2 - z^3 + O(z^4) >>> s = L(degree=Integer(1), constant=Integer(1)) >>> s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
L.<z> = LazyLaurentSeriesRing(QQ) (2*z).revert() (2/z).revert() (z-z^2).revert() s = L(degree=1, constant=-1) s.revert() s = L(degree=1, constant=1) s.revert()
Warning
For series not known to be eventually constant (e.g., being defined by a function) with approximate valuation \(\leq 1\) (but not necessarily its true valuation), this assumes that this is the actual valuation:
sage: f = L(lambda n: n if n > 2 else 0, valuation=1) sage: f.revert() <repr(... failed: ValueError: inverse does not exist>
>>> from sage.all import * >>> f = L(lambda n: n if n > Integer(2) else Integer(0), valuation=Integer(1)) >>> f.revert() <repr(... failed: ValueError: inverse does not exist>
f = L(lambda n: n if n > 2 else 0, valuation=1) f.revert()
- derivative(*args)[source]¶
Return the derivative of the Laurent series.
Multiple variables and iteration counts may be supplied; see the documentation of
sage.calculus.functional.derivative()function for details.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: z.derivative() 1 sage: (1+z+z^2).derivative(3) 0 sage: (1/z).derivative() -z^-2 sage: (1/(1-z)).derivative(z) 1 + 2*z + 3*z^2 + 4*z^3 + 5*z^4 + 6*z^5 + 7*z^6 + O(z^7)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> z.derivative() 1 >>> (Integer(1)+z+z**Integer(2)).derivative(Integer(3)) 0 >>> (Integer(1)/z).derivative() -z^-2 >>> (Integer(1)/(Integer(1)-z)).derivative(z) 1 + 2*z + 3*z^2 + 4*z^3 + 5*z^4 + 6*z^5 + 7*z^6 + O(z^7)
L.<z> = LazyLaurentSeriesRing(ZZ) z.derivative() (1+z+z^2).derivative(3) (1/z).derivative() (1/(1-z)).derivative(z)
- integral(variable, constants=None)[source]¶
Return the integral of
selfwith respect tovariable.INPUT:
variable– (optional) the variable to integrateconstants– (optional; keyword-only) list of integration constants for the integrals ofself(the last constant corresponds to the first integral)
If the first argument is a list, then this method iterprets it as integration constants. If it is a positive integer, the method interprets it as the number of times to integrate the function. If
variableis not the variable of the Laurent series, then the coefficients are integrated with respect tovariable.If the integration constants are not specified, they are considered to be \(0\).
EXAMPLES:
sage: L.<t> = LazyLaurentSeriesRing(QQ) sage: f = t^-3 + 2 + 3*t + t^5 sage: f.integral() -1/2*t^-2 + 2*t + 3/2*t^2 + 1/6*t^6 sage: f.integral([-2, -2]) 1/2*t^-1 - 2 - 2*t + t^2 + 1/2*t^3 + 1/42*t^7 sage: f.integral(t) -1/2*t^-2 + 2*t + 3/2*t^2 + 1/6*t^6 sage: f.integral(2) 1/2*t^-1 + t^2 + 1/2*t^3 + 1/42*t^7 sage: L.zero().integral() 0 sage: L.zero().integral([0, 1, 2, 3]) t + t^2 + 1/2*t^3
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('t',)); (t,) = L._first_ngens(1) >>> f = t**-Integer(3) + Integer(2) + Integer(3)*t + t**Integer(5) >>> f.integral() -1/2*t^-2 + 2*t + 3/2*t^2 + 1/6*t^6 >>> f.integral([-Integer(2), -Integer(2)]) 1/2*t^-1 - 2 - 2*t + t^2 + 1/2*t^3 + 1/42*t^7 >>> f.integral(t) -1/2*t^-2 + 2*t + 3/2*t^2 + 1/6*t^6 >>> f.integral(Integer(2)) 1/2*t^-1 + t^2 + 1/2*t^3 + 1/42*t^7 >>> L.zero().integral() 0 >>> L.zero().integral([Integer(0), Integer(1), Integer(2), Integer(3)]) t + t^2 + 1/2*t^3
L.<t> = LazyLaurentSeriesRing(QQ) f = t^-3 + 2 + 3*t + t^5 f.integral() f.integral([-2, -2]) f.integral(t) f.integral(2) L.zero().integral() L.zero().integral([0, 1, 2, 3])
We solve the ODE \(f' = a f\) by integrating both sides and the recursive definition:
sage: R.<a, C> = QQ[] sage: L.<x> = LazyLaurentSeriesRing(R) sage: f = L.undefined(0) sage: f.define((a*f).integral(constants=[C])) sage: f C + a*C*x + 1/2*a^2*C*x^2 + 1/6*a^3*C*x^3 + 1/24*a^4*C*x^4 + 1/120*a^5*C*x^5 + 1/720*a^6*C*x^6 + O(x^7) sage: C * exp(a*x) C + a*C*x + 1/2*a^2*C*x^2 + 1/6*a^3*C*x^3 + 1/24*a^4*C*x^4 + 1/120*a^5*C*x^5 + 1/720*a^6*C*x^6 + O(x^7)
>>> from sage.all import * >>> R = QQ['a, C']; (a, C,) = R._first_ngens(2) >>> L = LazyLaurentSeriesRing(R, names=('x',)); (x,) = L._first_ngens(1) >>> f = L.undefined(Integer(0)) >>> f.define((a*f).integral(constants=[C])) >>> f C + a*C*x + 1/2*a^2*C*x^2 + 1/6*a^3*C*x^3 + 1/24*a^4*C*x^4 + 1/120*a^5*C*x^5 + 1/720*a^6*C*x^6 + O(x^7) >>> C * exp(a*x) C + a*C*x + 1/2*a^2*C*x^2 + 1/6*a^3*C*x^3 + 1/24*a^4*C*x^4 + 1/120*a^5*C*x^5 + 1/720*a^6*C*x^6 + O(x^7)
R.<a, C> = QQ[] L.<x> = LazyLaurentSeriesRing(R) f = L.undefined(0) f.define((a*f).integral(constants=[C])) f C * exp(a*x)
We can integrate both the series and coefficients:
sage: R.<x,y,z> = QQ[] sage: L.<t> = LazyLaurentSeriesRing(R) sage: f = (x*t^2 + y*t^-2 + z)^2; f y^2*t^-4 + 2*y*z*t^-2 + (2*x*y + z^2) + 2*x*z*t^2 + x^2*t^4 sage: f.integral(x) x*y^2*t^-4 + 2*x*y*z*t^-2 + (x^2*y + x*z^2) + x^2*z*t^2 + 1/3*x^3*t^4 sage: f.integral(t) -1/3*y^2*t^-3 - 2*y*z*t^-1 + (2*x*y + z^2)*t + 2/3*x*z*t^3 + 1/5*x^2*t^5 sage: f.integral(y, constants=[x*y*z]) -1/9*y^3*t^-3 - y^2*z*t^-1 + x*y*z + (x*y^2 + y*z^2)*t + 2/3*x*y*z*t^3 + 1/5*x^2*y*t^5
>>> from sage.all import * >>> R = QQ['x, y, z']; (x, y, z,) = R._first_ngens(3) >>> L = LazyLaurentSeriesRing(R, names=('t',)); (t,) = L._first_ngens(1) >>> f = (x*t**Integer(2) + y*t**-Integer(2) + z)**Integer(2); f y^2*t^-4 + 2*y*z*t^-2 + (2*x*y + z^2) + 2*x*z*t^2 + x^2*t^4 >>> f.integral(x) x*y^2*t^-4 + 2*x*y*z*t^-2 + (x^2*y + x*z^2) + x^2*z*t^2 + 1/3*x^3*t^4 >>> f.integral(t) -1/3*y^2*t^-3 - 2*y*z*t^-1 + (2*x*y + z^2)*t + 2/3*x*z*t^3 + 1/5*x^2*t^5 >>> f.integral(y, constants=[x*y*z]) -1/9*y^3*t^-3 - y^2*z*t^-1 + x*y*z + (x*y^2 + y*z^2)*t + 2/3*x*y*z*t^3 + 1/5*x^2*y*t^5
R.<x,y,z> = QQ[] L.<t> = LazyLaurentSeriesRing(R) f = (x*t^2 + y*t^-2 + z)^2; f f.integral(x) f.integral(t) f.integral(y, constants=[x*y*z])
- is_unit()[source]¶
Return whether this element is a unit in the ring.
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: (2*z).is_unit() False sage: (1 + 2*z).is_unit() True sage: (1 + 2*z^-1).is_unit() False sage: (z^3 + 4 - z^-2).is_unit() True
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> (Integer(2)*z).is_unit() False >>> (Integer(1) + Integer(2)*z).is_unit() True >>> (Integer(1) + Integer(2)*z**-Integer(1)).is_unit() False >>> (z**Integer(3) + Integer(4) - z**-Integer(2)).is_unit() True
L.<z> = LazyLaurentSeriesRing(ZZ) (2*z).is_unit() (1 + 2*z).is_unit() (1 + 2*z^-1).is_unit() (z^3 + 4 - z^-2).is_unit()
- polynomial(degree=None, name=None)[source]¶
Return
selfas a Laurent polynomial ifselfis actually so.INPUT:
degree–Noneor an integername– name of the variable; if it isNone, the name of the variable of the series is used
OUTPUT:
A Laurent polynomial if the valuation of the series is negative or a polynomial otherwise.
If
degreeis notNone, the terms of the series of degree greater thandegreeare first truncated. IfdegreeisNoneand the series is not a polynomial or a Laurent polynomial, aValueErroris raised.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: f = L([1,0,0,2,0,0,0,3], valuation=5); f z^5 + 2*z^8 + 3*z^12 sage: f.polynomial() 3*z^12 + 2*z^8 + z^5
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> f = L([Integer(1),Integer(0),Integer(0),Integer(2),Integer(0),Integer(0),Integer(0),Integer(3)], valuation=Integer(5)); f z^5 + 2*z^8 + 3*z^12 >>> f.polynomial() 3*z^12 + 2*z^8 + z^5
L.<z> = LazyLaurentSeriesRing(ZZ) f = L([1,0,0,2,0,0,0,3], valuation=5); f f.polynomial()
- revert()[source]¶
Return the compositional inverse of
self.Given a Laurent series \(f\), the compositional inverse is a Laurent series \(g\) over the same base ring, such that \((f \circ g)(z) = f(g(z)) = z\).
The compositional inverse exists if and only if:
\(\mathrm{val}(f) = 1\), or
\(f = a + b z\) with \(a, b \neq 0\), or
\(f = a/z\) with \(a \neq 0\).
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: (2*z).revert() 1/2*z sage: (2/z).revert() 2*z^-1 sage: (z-z^2).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) sage: s = L(degree=1, constant=-1) sage: s.revert() -z - z^2 - z^3 + O(z^4) sage: s = L(degree=1, constant=1) sage: s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> (Integer(2)*z).revert() 1/2*z >>> (Integer(2)/z).revert() 2*z^-1 >>> (z-z**Integer(2)).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) >>> s = L(degree=Integer(1), constant=-Integer(1)) >>> s.revert() -z - z^2 - z^3 + O(z^4) >>> s = L(degree=Integer(1), constant=Integer(1)) >>> s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
L.<z> = LazyLaurentSeriesRing(QQ) (2*z).revert() (2/z).revert() (z-z^2).revert() s = L(degree=1, constant=-1) s.revert() s = L(degree=1, constant=1) s.revert()
Warning
For series not known to be eventually constant (e.g., being defined by a function) with approximate valuation \(\leq 1\) (but not necessarily its true valuation), this assumes that this is the actual valuation:
sage: f = L(lambda n: n if n > 2 else 0, valuation=1) sage: f.revert() <repr(... failed: ValueError: inverse does not exist>
>>> from sage.all import * >>> f = L(lambda n: n if n > Integer(2) else Integer(0), valuation=Integer(1)) >>> f.revert() <repr(... failed: ValueError: inverse does not exist>
f = L(lambda n: n if n > 2 else 0, valuation=1) f.revert()
- class sage.rings.lazy_series.LazyModuleElement(parent, coeff_stream)[source]¶
Bases:
ElementA lazy sequence with a module structure given by term-wise addition and scalar multiplication.
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: M = L(lambda n: n, valuation=0) sage: N = L(lambda n: 1, valuation=0) sage: M[0:10] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] sage: N[0:10] [1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> M = L(lambda n: n, valuation=Integer(0)) >>> N = L(lambda n: Integer(1), valuation=Integer(0)) >>> M[Integer(0):Integer(10)] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> N[Integer(0):Integer(10)] [1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
L.<z> = LazyLaurentSeriesRing(ZZ) M = L(lambda n: n, valuation=0) N = L(lambda n: 1, valuation=0) M[0:10] N[0:10]
Two sequences can be added:
sage: O = M + N sage: O[0:10] [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> from sage.all import * >>> O = M + N >>> O[Integer(0):Integer(10)] [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
O = M + N O[0:10]
Two sequences can be subtracted:
sage: P = M - N sage: P[0:10] [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8]
>>> from sage.all import * >>> P = M - N >>> P[Integer(0):Integer(10)] [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8]
P = M - N P[0:10]
A sequence can be multiplied by a scalar:
sage: Q = 2 * M sage: Q[0:10] [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
>>> from sage.all import * >>> Q = Integer(2) * M >>> Q[Integer(0):Integer(10)] [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
Q = 2 * M Q[0:10]
The negation of a sequence can also be found:
sage: R = -M sage: R[0:10] [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
>>> from sage.all import * >>> R = -M >>> R[Integer(0):Integer(10)] [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
R = -M R[0:10]
- arccos()[source]¶
Return the arccosine of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(RR) sage: arccos(z) # needs sage.symbolic 1.57079632679490 - 1.00000000000000*z + 0.000000000000000*z^2 - 0.166666666666667*z^3 + 0.000000000000000*z^4 - 0.0750000000000000*z^5 + O(1.00000000000000*z^7) sage: L.<z> = LazyLaurentSeriesRing(SR) # needs sage.symbolic sage: arccos(z/(1-z)) # needs sage.symbolic 1/2*pi - z - z^2 - 7/6*z^3 - 3/2*z^4 - 83/40*z^5 - 73/24*z^6 + O(z^7) sage: L.<x,y> = LazyPowerSeriesRing(SR) # needs sage.symbolic sage: arccos(x/(1-y)) # needs sage.symbolic 1/2*pi + (-x) + (-x*y) + ((-1/6)*x^3-x*y^2) + ((-1/2)*x^3*y-x*y^3) + ((-3/40)*x^5-x^3*y^2-x*y^4) + ((-3/8)*x^5*y+(-5/3)*x^3*y^3-x*y^5) + O(x,y)^7
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(RR, names=('z',)); (z,) = L._first_ngens(1) >>> arccos(z) # needs sage.symbolic 1.57079632679490 - 1.00000000000000*z + 0.000000000000000*z^2 - 0.166666666666667*z^3 + 0.000000000000000*z^4 - 0.0750000000000000*z^5 + O(1.00000000000000*z^7) >>> L = LazyLaurentSeriesRing(SR, names=('z',)); (z,) = L._first_ngens(1)# needs sage.symbolic >>> arccos(z/(Integer(1)-z)) # needs sage.symbolic 1/2*pi - z - z^2 - 7/6*z^3 - 3/2*z^4 - 83/40*z^5 - 73/24*z^6 + O(z^7) >>> L = LazyPowerSeriesRing(SR, names=('x', 'y',)); (x, y,) = L._first_ngens(2)# needs sage.symbolic >>> arccos(x/(Integer(1)-y)) # needs sage.symbolic 1/2*pi + (-x) + (-x*y) + ((-1/6)*x^3-x*y^2) + ((-1/2)*x^3*y-x*y^3) + ((-3/40)*x^5-x^3*y^2-x*y^4) + ((-3/8)*x^5*y+(-5/3)*x^3*y^3-x*y^5) + O(x,y)^7
L.<z> = LazyLaurentSeriesRing(RR) arccos(z) # needs sage.symbolic L.<z> = LazyLaurentSeriesRing(SR) # needs sage.symbolic arccos(z/(1-z)) # needs sage.symbolic L.<x,y> = LazyPowerSeriesRing(SR) # needs sage.symbolic arccos(x/(1-y)) # needs sage.symbolic
- arccot()[source]¶
Return the arctangent of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(RR) sage: arccot(z) # needs sage.symbolic 1.57079632679490 - 1.00000000000000*z + 0.000000000000000*z^2 + 0.333333333333333*z^3 + 0.000000000000000*z^4 - 0.200000000000000*z^5 + O(1.00000000000000*z^7) sage: L.<z> = LazyLaurentSeriesRing(SR) # needs sage.symbolic sage: arccot(z/(1-z)) # needs sage.symbolic 1/2*pi - z - z^2 - 2/3*z^3 + 4/5*z^5 + 4/3*z^6 + O(z^7) sage: L.<x,y> = LazyPowerSeriesRing(SR) # needs sage.symbolic sage: acot(x/(1-y)) # needs sage.symbolic 1/2*pi + (-x) + (-x*y) + (1/3*x^3-x*y^2) + (x^3*y-x*y^3) + ((-1/5)*x^5+2*x^3*y^2-x*y^4) + (-x^5*y+10/3*x^3*y^3-x*y^5) + O(x,y)^7
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(RR, names=('z',)); (z,) = L._first_ngens(1) >>> arccot(z) # needs sage.symbolic 1.57079632679490 - 1.00000000000000*z + 0.000000000000000*z^2 + 0.333333333333333*z^3 + 0.000000000000000*z^4 - 0.200000000000000*z^5 + O(1.00000000000000*z^7) >>> L = LazyLaurentSeriesRing(SR, names=('z',)); (z,) = L._first_ngens(1)# needs sage.symbolic >>> arccot(z/(Integer(1)-z)) # needs sage.symbolic 1/2*pi - z - z^2 - 2/3*z^3 + 4/5*z^5 + 4/3*z^6 + O(z^7) >>> L = LazyPowerSeriesRing(SR, names=('x', 'y',)); (x, y,) = L._first_ngens(2)# needs sage.symbolic >>> acot(x/(Integer(1)-y)) # needs sage.symbolic 1/2*pi + (-x) + (-x*y) + (1/3*x^3-x*y^2) + (x^3*y-x*y^3) + ((-1/5)*x^5+2*x^3*y^2-x*y^4) + (-x^5*y+10/3*x^3*y^3-x*y^5) + O(x,y)^7
L.<z> = LazyLaurentSeriesRing(RR) arccot(z) # needs sage.symbolic L.<z> = LazyLaurentSeriesRing(SR) # needs sage.symbolic arccot(z/(1-z)) # needs sage.symbolic L.<x,y> = LazyPowerSeriesRing(SR) # needs sage.symbolic acot(x/(1-y)) # needs sage.symbolic
- arcsin()[source]¶
Return the arcsine of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: arcsin(z) z + 1/6*z^3 + 3/40*z^5 + 5/112*z^7 + O(z^8) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: asin(x/(1-y)) x + x*y + (1/6*x^3+x*y^2) + (1/2*x^3*y+x*y^3) + (3/40*x^5+x^3*y^2+x*y^4) + (3/8*x^5*y+5/3*x^3*y^3+x*y^5) + (5/112*x^7+9/8*x^5*y^2+5/2*x^3*y^4+x*y^6) + O(x,y)^8
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> arcsin(z) z + 1/6*z^3 + 3/40*z^5 + 5/112*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> asin(x/(Integer(1)-y)) x + x*y + (1/6*x^3+x*y^2) + (1/2*x^3*y+x*y^3) + (3/40*x^5+x^3*y^2+x*y^4) + (3/8*x^5*y+5/3*x^3*y^3+x*y^5) + (5/112*x^7+9/8*x^5*y^2+5/2*x^3*y^4+x*y^6) + O(x,y)^8
L.<z> = LazyLaurentSeriesRing(QQ) arcsin(z) L.<x,y> = LazyPowerSeriesRing(QQ) asin(x/(1-y))
- arcsinh()[source]¶
Return the inverse of the hyperbolic sine of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: asinh(z) z - 1/6*z^3 + 3/40*z^5 - 5/112*z^7 + O(z^8)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> asinh(z) z - 1/6*z^3 + 3/40*z^5 - 5/112*z^7 + O(z^8)
L.<z> = LazyLaurentSeriesRing(QQ) asinh(z)
arcsinhis an alias:sage: arcsinh(z) z - 1/6*z^3 + 3/40*z^5 - 5/112*z^7 + O(z^8) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: asinh(x/(1-y)) x + x*y + (-1/6*x^3+x*y^2) + (-1/2*x^3*y+x*y^3) + (3/40*x^5-x^3*y^2+x*y^4) + (3/8*x^5*y-5/3*x^3*y^3+x*y^5) + (-5/112*x^7+9/8*x^5*y^2-5/2*x^3*y^4+x*y^6) + O(x,y)^8
>>> from sage.all import * >>> arcsinh(z) z - 1/6*z^3 + 3/40*z^5 - 5/112*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> asinh(x/(Integer(1)-y)) x + x*y + (-1/6*x^3+x*y^2) + (-1/2*x^3*y+x*y^3) + (3/40*x^5-x^3*y^2+x*y^4) + (3/8*x^5*y-5/3*x^3*y^3+x*y^5) + (-5/112*x^7+9/8*x^5*y^2-5/2*x^3*y^4+x*y^6) + O(x,y)^8
arcsinh(z) L.<x,y> = LazyPowerSeriesRing(QQ) asinh(x/(1-y))
- arctan()[source]¶
Return the arctangent of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: arctan(z) z - 1/3*z^3 + 1/5*z^5 - 1/7*z^7 + O(z^8) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: atan(x/(1-y)) x + x*y + (-1/3*x^3+x*y^2) + (-x^3*y+x*y^3) + (1/5*x^5-2*x^3*y^2+x*y^4) + (x^5*y-10/3*x^3*y^3+x*y^5) + (-1/7*x^7+3*x^5*y^2-5*x^3*y^4+x*y^6) + O(x,y)^8
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> arctan(z) z - 1/3*z^3 + 1/5*z^5 - 1/7*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> atan(x/(Integer(1)-y)) x + x*y + (-1/3*x^3+x*y^2) + (-x^3*y+x*y^3) + (1/5*x^5-2*x^3*y^2+x*y^4) + (x^5*y-10/3*x^3*y^3+x*y^5) + (-1/7*x^7+3*x^5*y^2-5*x^3*y^4+x*y^6) + O(x,y)^8
L.<z> = LazyLaurentSeriesRing(QQ) arctan(z) L.<x,y> = LazyPowerSeriesRing(QQ) atan(x/(1-y))
- arctanh()[source]¶
Return the inverse of the hyperbolic tangent of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: atanh(z) z + 1/3*z^3 + 1/5*z^5 + 1/7*z^7 + O(z^8)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> atanh(z) z + 1/3*z^3 + 1/5*z^5 + 1/7*z^7 + O(z^8)
L.<z> = LazyLaurentSeriesRing(QQ) atanh(z)
arctanhis an alias:sage: arctanh(z) z + 1/3*z^3 + 1/5*z^5 + 1/7*z^7 + O(z^8) sage: L.<x, y> = LazyPowerSeriesRing(QQ) sage: atanh(x/(1-y)) x + x*y + (1/3*x^3+x*y^2) + (x^3*y+x*y^3) + (1/5*x^5+2*x^3*y^2+x*y^4) + (x^5*y+10/3*x^3*y^3+x*y^5) + (1/7*x^7+3*x^5*y^2+5*x^3*y^4+x*y^6) + O(x,y)^8
>>> from sage.all import * >>> arctanh(z) z + 1/3*z^3 + 1/5*z^5 + 1/7*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> atanh(x/(Integer(1)-y)) x + x*y + (1/3*x^3+x*y^2) + (x^3*y+x*y^3) + (1/5*x^5+2*x^3*y^2+x*y^4) + (x^5*y+10/3*x^3*y^3+x*y^5) + (1/7*x^7+3*x^5*y^2+5*x^3*y^4+x*y^6) + O(x,y)^8
arctanh(z) L.<x, y> = LazyPowerSeriesRing(QQ) atanh(x/(1-y))
- change_ring(ring)[source]¶
Return
selfwith coefficients converted to elements ofring.INPUT:
ring– a ring
EXAMPLES:
Dense Implementation:
sage: L.<z> = LazyLaurentSeriesRing(ZZ, sparse=False) sage: s = 2 + z sage: t = s.change_ring(QQ) sage: t^-1 1/2 - 1/4*z + 1/8*z^2 - 1/16*z^3 + 1/32*z^4 - 1/64*z^5 + 1/128*z^6 + O(z^7) sage: M = L(lambda n: n, valuation=0); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) sage: N = M.change_ring(QQ) sage: N.parent() Lazy Laurent Series Ring in z over Rational Field sage: M.parent() Lazy Laurent Series Ring in z over Integer Ring
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, sparse=False, names=('z',)); (z,) = L._first_ngens(1) >>> s = Integer(2) + z >>> t = s.change_ring(QQ) >>> t**-Integer(1) 1/2 - 1/4*z + 1/8*z^2 - 1/16*z^3 + 1/32*z^4 - 1/64*z^5 + 1/128*z^6 + O(z^7) >>> M = L(lambda n: n, valuation=Integer(0)); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) >>> N = M.change_ring(QQ) >>> N.parent() Lazy Laurent Series Ring in z over Rational Field >>> M.parent() Lazy Laurent Series Ring in z over Integer Ring
L.<z> = LazyLaurentSeriesRing(ZZ, sparse=False) s = 2 + z t = s.change_ring(QQ) t^-1 M = L(lambda n: n, valuation=0); M N = M.change_ring(QQ) N.parent() M.parent()
Sparse Implementation:
sage: L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) sage: M = L(lambda n: n, valuation=0); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) sage: M.parent() Lazy Laurent Series Ring in z over Integer Ring sage: N = M.change_ring(QQ) sage: N.parent() Lazy Laurent Series Ring in z over Rational Field sage: M^-1 z^-1 - 2 + z + O(z^6)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, sparse=True, names=('z',)); (z,) = L._first_ngens(1) >>> M = L(lambda n: n, valuation=Integer(0)); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) >>> M.parent() Lazy Laurent Series Ring in z over Integer Ring >>> N = M.change_ring(QQ) >>> N.parent() Lazy Laurent Series Ring in z over Rational Field >>> M**-Integer(1) z^-1 - 2 + z + O(z^6)
L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) M = L(lambda n: n, valuation=0); M M.parent() N = M.change_ring(QQ) N.parent() M^-1
A Dirichlet series example:
sage: L = LazyDirichletSeriesRing(ZZ, 'z') sage: s = L(constant=2) sage: t = s.change_ring(QQ) sage: t.parent() Lazy Dirichlet Series Ring in z over Rational Field sage: it = t^-1 sage: it # needs sage.symbolic 1/2 - 1/2/2^z - 1/2/3^z - 1/2/5^z + 1/2/6^z - 1/2/7^z + O(1/(8^z))
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(ZZ, 'z') >>> s = L(constant=Integer(2)) >>> t = s.change_ring(QQ) >>> t.parent() Lazy Dirichlet Series Ring in z over Rational Field >>> it = t**-Integer(1) >>> it # needs sage.symbolic 1/2 - 1/2/2^z - 1/2/3^z - 1/2/5^z + 1/2/6^z - 1/2/7^z + O(1/(8^z))
L = LazyDirichletSeriesRing(ZZ, 'z') s = L(constant=2) t = s.change_ring(QQ) t.parent() it = t^-1 it # needs sage.symbolic
A Taylor series example:
sage: L.<z> = LazyPowerSeriesRing(ZZ) sage: s = 2 + z sage: t = s.change_ring(QQ) sage: t^-1 1/2 - 1/4*z + 1/8*z^2 - 1/16*z^3 + 1/32*z^4 - 1/64*z^5 + 1/128*z^6 + O(z^7) sage: t.parent() Lazy Taylor Series Ring in z over Rational Field
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> s = Integer(2) + z >>> t = s.change_ring(QQ) >>> t**-Integer(1) 1/2 - 1/4*z + 1/8*z^2 - 1/16*z^3 + 1/32*z^4 - 1/64*z^5 + 1/128*z^6 + O(z^7) >>> t.parent() Lazy Taylor Series Ring in z over Rational Field
L.<z> = LazyPowerSeriesRing(ZZ) s = 2 + z t = s.change_ring(QQ) t^-1 t.parent()
- coefficient(n)[source]¶
Return the homogeneous degree
npart of the series.INPUT:
n– integer; the degree
For a series
f, the slicef[start:stop]produces the following:if
startandstopare integers, return the list of terms with given degreesif
startisNone, return the list of terms beginning with the valuationif
stopisNone, return alazy_list_genericinstead.
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: f = z / (1 - 2*z^3) sage: [f[n] for n in range(20)] [0, 1, 0, 0, 2, 0, 0, 4, 0, 0, 8, 0, 0, 16, 0, 0, 32, 0, 0, 64] sage: f[0:20] [0, 1, 0, 0, 2, 0, 0, 4, 0, 0, 8, 0, 0, 16, 0, 0, 32, 0, 0, 64] sage: f[:20] [1, 0, 0, 2, 0, 0, 4, 0, 0, 8, 0, 0, 16, 0, 0, 32, 0, 0, 64] sage: f[::3] lazy list [1, 2, 4, ...] sage: M = L(lambda n: n, valuation=0) sage: [M[n] for n in range(20)] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19] sage: L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) sage: M = L(lambda n: n, valuation=0) sage: [M[n] for n in range(20)] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> f = z / (Integer(1) - Integer(2)*z**Integer(3)) >>> [f[n] for n in range(Integer(20))] [0, 1, 0, 0, 2, 0, 0, 4, 0, 0, 8, 0, 0, 16, 0, 0, 32, 0, 0, 64] >>> f[Integer(0):Integer(20)] [0, 1, 0, 0, 2, 0, 0, 4, 0, 0, 8, 0, 0, 16, 0, 0, 32, 0, 0, 64] >>> f[:Integer(20)] [1, 0, 0, 2, 0, 0, 4, 0, 0, 8, 0, 0, 16, 0, 0, 32, 0, 0, 64] >>> f[::Integer(3)] lazy list [1, 2, 4, ...] >>> M = L(lambda n: n, valuation=Integer(0)) >>> [M[n] for n in range(Integer(20))] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19] >>> L = LazyLaurentSeriesRing(ZZ, sparse=True, names=('z',)); (z,) = L._first_ngens(1) >>> M = L(lambda n: n, valuation=Integer(0)) >>> [M[n] for n in range(Integer(20))] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
L.<z> = LazyLaurentSeriesRing(ZZ) f = z / (1 - 2*z^3) [f[n] for n in range(20)] f[0:20] f[:20] f[::3] M = L(lambda n: n, valuation=0) [M[n] for n in range(20)] L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) M = L(lambda n: n, valuation=0) [M[n] for n in range(20)]
Similarly for multivariate series:
sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: sin(x*y)[:11] [x*y, 0, 0, 0, -1/6*x^3*y^3, 0, 0, 0, 1/120*x^5*y^5] sage: sin(x*y)[2::4] lazy list [x*y, -1/6*x^3*y^3, 1/120*x^5*y^5, ...]
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> sin(x*y)[:Integer(11)] [x*y, 0, 0, 0, -1/6*x^3*y^3, 0, 0, 0, 1/120*x^5*y^5] >>> sin(x*y)[Integer(2)::Integer(4)] lazy list [x*y, -1/6*x^3*y^3, 1/120*x^5*y^5, ...]
L.<x,y> = LazyPowerSeriesRing(QQ) sin(x*y)[:11] sin(x*y)[2::4]
Similarly for Dirichlet series:
sage: L = LazyDirichletSeriesRing(ZZ, "z") sage: L(lambda n: n)[1:11] [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(ZZ, "z") >>> L(lambda n: n)[Integer(1):Integer(11)] [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
L = LazyDirichletSeriesRing(ZZ, "z") L(lambda n: n)[1:11]
- coefficients(n=None)[source]¶
Return the first \(n\) nonzero coefficients of
self.INPUT:
n– (optional) the number of nonzero coefficients to return
If the series has fewer than \(n\) nonzero coefficients, only these are returned.
If
nisNone, alazy_list_genericwith all nonzero coefficients is returned instead.Warning
If there are fewer than \(n\) nonzero coefficients, but this cannot be detected, this method will not return.
EXAMPLES:
sage: L.<x> = LazyPowerSeriesRing(QQ) sage: f = L([1,2,3]) sage: f.coefficients(5) doctest:...: DeprecationWarning: the method coefficients now only returns the nonzero coefficients. Use __getitem__ instead. See https://github.com/sagemath/sage/issues/32367 for details. [1, 2, 3] sage: f = sin(x) sage: f.coefficients(5) [1, -1/6, 1/120, -1/5040, 1/362880] sage: L.<x, y> = LazyPowerSeriesRing(QQ) sage: f = sin(x^2+y^2) sage: f.coefficients(5) [1, 1, -1/6, -1/2, -1/2] sage: f.coefficients() lazy list [1, 1, -1/6, ...] sage: L.<x> = LazyPowerSeriesRing(GF(2)) sage: f = L(lambda n: n) sage: f.coefficients(5) [1, 1, 1, 1, 1]
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x',)); (x,) = L._first_ngens(1) >>> f = L([Integer(1),Integer(2),Integer(3)]) >>> f.coefficients(Integer(5)) doctest:...: DeprecationWarning: the method coefficients now only returns the nonzero coefficients. Use __getitem__ instead. See https://github.com/sagemath/sage/issues/32367 for details. [1, 2, 3] >>> f = sin(x) >>> f.coefficients(Integer(5)) [1, -1/6, 1/120, -1/5040, 1/362880] >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> f = sin(x**Integer(2)+y**Integer(2)) >>> f.coefficients(Integer(5)) [1, 1, -1/6, -1/2, -1/2] >>> f.coefficients() lazy list [1, 1, -1/6, ...] >>> L = LazyPowerSeriesRing(GF(Integer(2)), names=('x',)); (x,) = L._first_ngens(1) >>> f = L(lambda n: n) >>> f.coefficients(Integer(5)) [1, 1, 1, 1, 1]
L.<x> = LazyPowerSeriesRing(QQ) f = L([1,2,3]) f.coefficients(5) f = sin(x) f.coefficients(5) L.<x, y> = LazyPowerSeriesRing(QQ) f = sin(x^2+y^2) f.coefficients(5) f.coefficients() L.<x> = LazyPowerSeriesRing(GF(2)) f = L(lambda n: n) f.coefficients(5)
- cos()[source]¶
Return the cosine of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: cos(z) 1 - 1/2*z^2 + 1/24*z^4 - 1/720*z^6 + O(z^7) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: cos(x/(1-y)).polynomial(4) 1/24*x^4 - 3/2*x^2*y^2 - x^2*y - 1/2*x^2 + 1
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> cos(z) 1 - 1/2*z^2 + 1/24*z^4 - 1/720*z^6 + O(z^7) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> cos(x/(Integer(1)-y)).polynomial(Integer(4)) 1/24*x^4 - 3/2*x^2*y^2 - x^2*y - 1/2*x^2 + 1
L.<z> = LazyLaurentSeriesRing(QQ) cos(z) L.<x,y> = LazyPowerSeriesRing(QQ) cos(x/(1-y)).polynomial(4)
- cosh()[source]¶
Return the hyperbolic cosine of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: cosh(z) 1 + 1/2*z^2 + 1/24*z^4 + 1/720*z^6 + O(z^7) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: cosh(x/(1-y)) 1 + 1/2*x^2 + x^2*y + (1/24*x^4+3/2*x^2*y^2) + (1/6*x^4*y+2*x^2*y^3) + (1/720*x^6+5/12*x^4*y^2+5/2*x^2*y^4) + O(x,y)^7
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> cosh(z) 1 + 1/2*z^2 + 1/24*z^4 + 1/720*z^6 + O(z^7) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> cosh(x/(Integer(1)-y)) 1 + 1/2*x^2 + x^2*y + (1/24*x^4+3/2*x^2*y^2) + (1/6*x^4*y+2*x^2*y^3) + (1/720*x^6+5/12*x^4*y^2+5/2*x^2*y^4) + O(x,y)^7
L.<z> = LazyLaurentSeriesRing(QQ) cosh(z) L.<x,y> = LazyPowerSeriesRing(QQ) cosh(x/(1-y))
- cot()[source]¶
Return the cotangent of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: cot(z) z^-1 - 1/3*z - 1/45*z^3 - 2/945*z^5 + O(z^6) sage: L.<x> = LazyLaurentSeriesRing(QQ) sage: cot(x/(1-x)).polynomial(4) x^-1 - 1 - 1/3*x - 1/3*x^2 - 16/45*x^3 - 2/5*x^4
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> cot(z) z^-1 - 1/3*z - 1/45*z^3 - 2/945*z^5 + O(z^6) >>> L = LazyLaurentSeriesRing(QQ, names=('x',)); (x,) = L._first_ngens(1) >>> cot(x/(Integer(1)-x)).polynomial(Integer(4)) x^-1 - 1 - 1/3*x - 1/3*x^2 - 16/45*x^3 - 2/5*x^4
L.<z> = LazyLaurentSeriesRing(QQ) cot(z) L.<x> = LazyLaurentSeriesRing(QQ) cot(x/(1-x)).polynomial(4)
- coth()[source]¶
Return the hyperbolic cotangent of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: coth(z) # needs sage.libs.flint z^-1 + 1/3*z - 1/45*z^3 + 2/945*z^5 + O(z^6) sage: coth(z + z^2) # needs sage.libs.flint z^-1 - 1 + 4/3*z - 2/3*z^2 + 44/45*z^3 - 16/15*z^4 + 884/945*z^5 + O(z^6)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> coth(z) # needs sage.libs.flint z^-1 + 1/3*z - 1/45*z^3 + 2/945*z^5 + O(z^6) >>> coth(z + z**Integer(2)) # needs sage.libs.flint z^-1 - 1 + 4/3*z - 2/3*z^2 + 44/45*z^3 - 16/15*z^4 + 884/945*z^5 + O(z^6)
L.<z> = LazyLaurentSeriesRing(QQ) coth(z) # needs sage.libs.flint coth(z + z^2) # needs sage.libs.flint
- csc()[source]¶
Return the cosecant of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: csc(z) z^-1 + 1/6*z + 7/360*z^3 + 31/15120*z^5 + O(z^6) sage: L.<x> = LazyLaurentSeriesRing(QQ) sage: csc(x/(1-x)).polynomial(4) x^-1 - 1 + 1/6*x + 1/6*x^2 + 67/360*x^3 + 9/40*x^4
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> csc(z) z^-1 + 1/6*z + 7/360*z^3 + 31/15120*z^5 + O(z^6) >>> L = LazyLaurentSeriesRing(QQ, names=('x',)); (x,) = L._first_ngens(1) >>> csc(x/(Integer(1)-x)).polynomial(Integer(4)) x^-1 - 1 + 1/6*x + 1/6*x^2 + 67/360*x^3 + 9/40*x^4
L.<z> = LazyLaurentSeriesRing(QQ) csc(z) L.<x> = LazyLaurentSeriesRing(QQ) csc(x/(1-x)).polynomial(4)
- csch()[source]¶
Return the hyperbolic cosecant of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: csch(z) # needs sage.libs.flint z^-1 - 1/6*z + 7/360*z^3 - 31/15120*z^5 + O(z^6) sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: csch(z/(1-z)) # needs sage.libs.flint z^-1 - 1 - 1/6*z - 1/6*z^2 - 53/360*z^3 - 13/120*z^4 - 787/15120*z^5 + O(z^6)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> csch(z) # needs sage.libs.flint z^-1 - 1/6*z + 7/360*z^3 - 31/15120*z^5 + O(z^6) >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> csch(z/(Integer(1)-z)) # needs sage.libs.flint z^-1 - 1 - 1/6*z - 1/6*z^2 - 53/360*z^3 - 13/120*z^4 - 787/15120*z^5 + O(z^6)
L.<z> = LazyLaurentSeriesRing(QQ) csch(z) # needs sage.libs.flint L.<z> = LazyLaurentSeriesRing(QQ) csch(z/(1-z)) # needs sage.libs.flint
- define(s)[source]¶
Define an equation by
self = s.INPUT:
s– a lazy series
EXAMPLES:
We begin by constructing the Catalan numbers:
sage: L.<z> = LazyPowerSeriesRing(ZZ) sage: C = L.undefined() sage: C.define(1 + z*C^2) sage: C 1 + z + 2*z^2 + 5*z^3 + 14*z^4 + 42*z^5 + 132*z^6 + O(z^7) sage: binomial(2000, 1000) / C[1000] # needs sage.symbolic 1001
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> C = L.undefined() >>> C.define(Integer(1) + z*C**Integer(2)) >>> C 1 + z + 2*z^2 + 5*z^3 + 14*z^4 + 42*z^5 + 132*z^6 + O(z^7) >>> binomial(Integer(2000), Integer(1000)) / C[Integer(1000)] # needs sage.symbolic 1001
L.<z> = LazyPowerSeriesRing(ZZ) C = L.undefined() C.define(1 + z*C^2) C binomial(2000, 1000) / C[1000] # needs sage.symbolic
The Catalan numbers but with a valuation \(1\):
sage: B = L.undefined(valuation=1) sage: B.define(z + B^2) sage: B z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8)
>>> from sage.all import * >>> B = L.undefined(valuation=Integer(1)) >>> B.define(z + B**Integer(2)) >>> B z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8)
B = L.undefined(valuation=1) B.define(z + B^2) B
We can define multiple series that are linked:
sage: s = L.undefined() sage: t = L.undefined() sage: s.define(1 + z*t^3) sage: t.define(1 + z*s^2) sage: s[0:9] [1, 1, 3, 9, 34, 132, 546, 2327, 10191] sage: t[0:9] [1, 1, 2, 7, 24, 95, 386, 1641, 7150]
>>> from sage.all import * >>> s = L.undefined() >>> t = L.undefined() >>> s.define(Integer(1) + z*t**Integer(3)) >>> t.define(Integer(1) + z*s**Integer(2)) >>> s[Integer(0):Integer(9)] [1, 1, 3, 9, 34, 132, 546, 2327, 10191] >>> t[Integer(0):Integer(9)] [1, 1, 2, 7, 24, 95, 386, 1641, 7150]
s = L.undefined() t = L.undefined() s.define(1 + z*t^3) t.define(1 + z*s^2) s[0:9] t[0:9]
A bigger example:
sage: L.<z> = LazyPowerSeriesRing(ZZ) sage: A = L.undefined(valuation=5) sage: B = L.undefined() sage: C = L.undefined(valuation=2) sage: A.define(z^5 + B^2) sage: B.define(z^5 + C^2) sage: C.define(z^2 + C^2 + A^2) sage: A[0:15] [0, 0, 0, 0, 0, 1, 0, 0, 1, 2, 5, 4, 14, 10, 48] sage: B[0:15] [0, 0, 0, 0, 1, 1, 2, 0, 5, 0, 14, 0, 44, 0, 138] sage: C[0:15] [0, 0, 1, 0, 1, 0, 2, 0, 5, 0, 15, 0, 44, 2, 142]
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> A = L.undefined(valuation=Integer(5)) >>> B = L.undefined() >>> C = L.undefined(valuation=Integer(2)) >>> A.define(z**Integer(5) + B**Integer(2)) >>> B.define(z**Integer(5) + C**Integer(2)) >>> C.define(z**Integer(2) + C**Integer(2) + A**Integer(2)) >>> A[Integer(0):Integer(15)] [0, 0, 0, 0, 0, 1, 0, 0, 1, 2, 5, 4, 14, 10, 48] >>> B[Integer(0):Integer(15)] [0, 0, 0, 0, 1, 1, 2, 0, 5, 0, 14, 0, 44, 0, 138] >>> C[Integer(0):Integer(15)] [0, 0, 1, 0, 1, 0, 2, 0, 5, 0, 15, 0, 44, 2, 142]
L.<z> = LazyPowerSeriesRing(ZZ) A = L.undefined(valuation=5) B = L.undefined() C = L.undefined(valuation=2) A.define(z^5 + B^2) B.define(z^5 + C^2) C.define(z^2 + C^2 + A^2) A[0:15] B[0:15] C[0:15]
Counting binary trees:
sage: L.<z> = LazyPowerSeriesRing(QQ) sage: s = L.undefined(valuation=1) sage: s.define(z + (s^2+s(z^2))/2) sage: s[0:9] [0, 1, 1, 1, 2, 3, 6, 11, 23]
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> s = L.undefined(valuation=Integer(1)) >>> s.define(z + (s**Integer(2)+s(z**Integer(2)))/Integer(2)) >>> s[Integer(0):Integer(9)] [0, 1, 1, 1, 2, 3, 6, 11, 23]
L.<z> = LazyPowerSeriesRing(QQ) s = L.undefined(valuation=1) s.define(z + (s^2+s(z^2))/2) s[0:9]
The \(q\)-Catalan numbers:
sage: R.<q> = ZZ[] sage: L.<z> = LazyLaurentSeriesRing(R) sage: s = L.undefined(valuation=0) sage: s.define(1+z*s*s(q*z)) sage: s 1 + z + (q + 1)*z^2 + (q^3 + q^2 + 2*q + 1)*z^3 + (q^6 + q^5 + 2*q^4 + 3*q^3 + 3*q^2 + 3*q + 1)*z^4 + (q^10 + q^9 + 2*q^8 + 3*q^7 + 5*q^6 + 5*q^5 + 7*q^4 + 7*q^3 + 6*q^2 + 4*q + 1)*z^5 + (q^15 + q^14 + 2*q^13 + 3*q^12 + 5*q^11 + 7*q^10 + 9*q^9 + 11*q^8 + 14*q^7 + 16*q^6 + 16*q^5 + 17*q^4 + 14*q^3 + 10*q^2 + 5*q + 1)*z^6 + O(z^7)
>>> from sage.all import * >>> R = ZZ['q']; (q,) = R._first_ngens(1) >>> L = LazyLaurentSeriesRing(R, names=('z',)); (z,) = L._first_ngens(1) >>> s = L.undefined(valuation=Integer(0)) >>> s.define(Integer(1)+z*s*s(q*z)) >>> s 1 + z + (q + 1)*z^2 + (q^3 + q^2 + 2*q + 1)*z^3 + (q^6 + q^5 + 2*q^4 + 3*q^3 + 3*q^2 + 3*q + 1)*z^4 + (q^10 + q^9 + 2*q^8 + 3*q^7 + 5*q^6 + 5*q^5 + 7*q^4 + 7*q^3 + 6*q^2 + 4*q + 1)*z^5 + (q^15 + q^14 + 2*q^13 + 3*q^12 + 5*q^11 + 7*q^10 + 9*q^9 + 11*q^8 + 14*q^7 + 16*q^6 + 16*q^5 + 17*q^4 + 14*q^3 + 10*q^2 + 5*q + 1)*z^6 + O(z^7)
R.<q> = ZZ[] L.<z> = LazyLaurentSeriesRing(R) s = L.undefined(valuation=0) s.define(1+z*s*s(q*z)) s
We count unlabeled ordered trees by total number of nodes and number of internal nodes:
sage: R.<q> = QQ[] sage: Q.<z> = LazyPowerSeriesRing(R) sage: leaf = z sage: internal_node = q * z sage: L = Q(constant=1, degree=1) sage: T = Q.undefined(valuation=1) sage: T.define(leaf + internal_node * L(T)) sage: T[0:6] [0, 1, q, q^2 + q, q^3 + 3*q^2 + q, q^4 + 6*q^3 + 6*q^2 + q]
>>> from sage.all import * >>> R = QQ['q']; (q,) = R._first_ngens(1) >>> Q = LazyPowerSeriesRing(R, names=('z',)); (z,) = Q._first_ngens(1) >>> leaf = z >>> internal_node = q * z >>> L = Q(constant=Integer(1), degree=Integer(1)) >>> T = Q.undefined(valuation=Integer(1)) >>> T.define(leaf + internal_node * L(T)) >>> T[Integer(0):Integer(6)] [0, 1, q, q^2 + q, q^3 + 3*q^2 + q, q^4 + 6*q^3 + 6*q^2 + q]
R.<q> = QQ[] Q.<z> = LazyPowerSeriesRing(R) leaf = z internal_node = q * z L = Q(constant=1, degree=1) T = Q.undefined(valuation=1) T.define(leaf + internal_node * L(T)) T[0:6]
Similarly for Dirichlet series:
sage: L = LazyDirichletSeriesRing(ZZ, "z") sage: g = L(constant=1, valuation=2) sage: F = L.undefined() sage: F.define(1 + g*F) sage: F[:16] [1, 1, 1, 2, 1, 3, 1, 4, 2, 3, 1, 8, 1, 3, 3] sage: oeis(_) # optional - internet 0: A002033: Number of perfect partitions of n. 1: A074206: Kalmár's [Kalmar's] problem: number of ordered factorizations of n. ... sage: F = L.undefined() sage: F.define(1 + g*F*F) sage: F[:16] [1, 1, 1, 3, 1, 5, 1, 10, 3, 5, 1, 24, 1, 5, 5]
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(ZZ, "z") >>> g = L(constant=Integer(1), valuation=Integer(2)) >>> F = L.undefined() >>> F.define(Integer(1) + g*F) >>> F[:Integer(16)] [1, 1, 1, 2, 1, 3, 1, 4, 2, 3, 1, 8, 1, 3, 3] >>> oeis(_) # optional - internet 0: A002033: Number of perfect partitions of n. 1: A074206: Kalmár's [Kalmar's] problem: number of ordered factorizations of n. ... >>> F = L.undefined() >>> F.define(Integer(1) + g*F*F) >>> F[:Integer(16)] [1, 1, 1, 3, 1, 5, 1, 10, 3, 5, 1, 24, 1, 5, 5]
L = LazyDirichletSeriesRing(ZZ, "z") g = L(constant=1, valuation=2) F = L.undefined() F.define(1 + g*F) F[:16] oeis(_) # optional - internet F = L.undefined() F.define(1 + g*F*F) F[:16]
We can compute the Frobenius character of unlabeled trees:
sage: # needs sage.combinat sage: m = SymmetricFunctions(QQ).m() sage: s = SymmetricFunctions(QQ).s() sage: L = LazySymmetricFunctions(m) sage: E = L(lambda n: s[n], valuation=0) sage: X = L(s[1]) sage: A = L.undefined() sage: A.define(X*E(A)) sage: A[:6] [m[1], 2*m[1, 1] + m[2], 9*m[1, 1, 1] + 5*m[2, 1] + 2*m[3], 64*m[1, 1, 1, 1] + 34*m[2, 1, 1] + 18*m[2, 2] + 13*m[3, 1] + 4*m[4], 625*m[1, 1, 1, 1, 1] + 326*m[2, 1, 1, 1] + 171*m[2, 2, 1] + 119*m[3, 1, 1] + 63*m[3, 2] + 35*m[4, 1] + 9*m[5]]
>>> from sage.all import * >>> # needs sage.combinat >>> m = SymmetricFunctions(QQ).m() >>> s = SymmetricFunctions(QQ).s() >>> L = LazySymmetricFunctions(m) >>> E = L(lambda n: s[n], valuation=Integer(0)) >>> X = L(s[Integer(1)]) >>> A = L.undefined() >>> A.define(X*E(A)) >>> A[:Integer(6)] [m[1], 2*m[1, 1] + m[2], 9*m[1, 1, 1] + 5*m[2, 1] + 2*m[3], 64*m[1, 1, 1, 1] + 34*m[2, 1, 1] + 18*m[2, 2] + 13*m[3, 1] + 4*m[4], 625*m[1, 1, 1, 1, 1] + 326*m[2, 1, 1, 1] + 171*m[2, 2, 1] + 119*m[3, 1, 1] + 63*m[3, 2] + 35*m[4, 1] + 9*m[5]]
# needs sage.combinat m = SymmetricFunctions(QQ).m() s = SymmetricFunctions(QQ).s() L = LazySymmetricFunctions(m) E = L(lambda n: s[n], valuation=0) X = L(s[1]) A = L.undefined() A.define(X*E(A)) A[:6]
- euler()[source]¶
Return the Euler function evaluated at
self.The Euler function is defined as
\[\phi(z) = (z; z)_{\infty} = \sum_{n=0}^{\infty} (-1)^n q^{(3n^2-n)/2}.\]EXAMPLES:
sage: L.<q> = LazyLaurentSeriesRing(ZZ) sage: phi = L.euler() sage: (q + q^2).euler() - phi(q + q^2) O(q^7)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('q',)); (q,) = L._first_ngens(1) >>> phi = L.euler() >>> (q + q**Integer(2)).euler() - phi(q + q**Integer(2)) O(q^7)
L.<q> = LazyLaurentSeriesRing(ZZ) phi = L.euler() (q + q^2).euler() - phi(q + q^2)
- exp()[source]¶
Return the exponential series of
self.EXAMPLES:
sage: L = LazyDirichletSeriesRing(QQ, "s") sage: Z = L(constant=1, valuation=2) sage: exp(Z) # needs sage.symbolic 1 + 1/(2^s) + 1/(3^s) + 3/2/4^s + 1/(5^s) + 2/6^s + 1/(7^s) + O(1/(8^s))
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(QQ, "s") >>> Z = L(constant=Integer(1), valuation=Integer(2)) >>> exp(Z) # needs sage.symbolic 1 + 1/(2^s) + 1/(3^s) + 3/2/4^s + 1/(5^s) + 2/6^s + 1/(7^s) + O(1/(8^s))
L = LazyDirichletSeriesRing(QQ, "s") Z = L(constant=1, valuation=2) exp(Z) # needs sage.symbolic
- hypergeometric(a, b)[source]¶
Return the \({}_{p}F_{q}\)-hypergeometric function \(\,_pF_{q}\) where \((p,q)\) is the parameterization of
self.INPUT:
a– the first parameter of the hypergeometric functionb– the second parameter of the hypergeometric function
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: z.hypergeometric([1, 1], [1]) 1 + z + z^2 + z^3 + z^4 + z^5 + z^6 + O(z^7) sage: z.hypergeometric([], []) - exp(z) O(z^7) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: (x+y).hypergeometric([1, 1], [1]).polynomial(4) x^4 + 4*x^3*y + 6*x^2*y^2 + 4*x*y^3 + y^4 + x^3 + 3*x^2*y + 3*x*y^2 + y^3 + x^2 + 2*x*y + y^2 + x + y + 1
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> z.hypergeometric([Integer(1), Integer(1)], [Integer(1)]) 1 + z + z^2 + z^3 + z^4 + z^5 + z^6 + O(z^7) >>> z.hypergeometric([], []) - exp(z) O(z^7) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> (x+y).hypergeometric([Integer(1), Integer(1)], [Integer(1)]).polynomial(Integer(4)) x^4 + 4*x^3*y + 6*x^2*y^2 + 4*x*y^3 + y^4 + x^3 + 3*x^2*y + 3*x*y^2 + y^3 + x^2 + 2*x*y + y^2 + x + y + 1
L.<z> = LazyLaurentSeriesRing(QQ) z.hypergeometric([1, 1], [1]) z.hypergeometric([], []) - exp(z) L.<x,y> = LazyPowerSeriesRing(QQ) (x+y).hypergeometric([1, 1], [1]).polynomial(4)
- is_nonzero(proof=False)[source]¶
Return
Trueifselfis known to be nonzero.INPUT:
proof– boolean (default:False); ifTrue, this will also return an index such thatselfhas a nonzero coefficient
Warning
If the stream is exactly zero, this will run forever.
EXAMPLES:
A series that it not known to be nonzero with no halting precision:
sage: L.<z> = LazyLaurentSeriesRing(GF(2)) sage: f = L(lambda n: 0, valuation=0) sage: f.is_nonzero() False sage: bool(f) True sage: g = L(lambda n: 0 if n < 50 else 1, valuation=2) sage: g.is_nonzero() False sage: g[60] 1 sage: g.is_nonzero() True
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(GF(Integer(2)), names=('z',)); (z,) = L._first_ngens(1) >>> f = L(lambda n: Integer(0), valuation=Integer(0)) >>> f.is_nonzero() False >>> bool(f) True >>> g = L(lambda n: Integer(0) if n < Integer(50) else Integer(1), valuation=Integer(2)) >>> g.is_nonzero() False >>> g[Integer(60)] 1 >>> g.is_nonzero() True
L.<z> = LazyLaurentSeriesRing(GF(2)) f = L(lambda n: 0, valuation=0) f.is_nonzero() bool(f) g = L(lambda n: 0 if n < 50 else 1, valuation=2) g.is_nonzero() g[60] g.is_nonzero()
With finite halting precision, it can be considered to be indistinguishable from zero until possibly enough coefficients are computed:
sage: L.options.halting_precision = 20 sage: f = L(lambda n: 0, valuation=0) sage: f.is_zero() True sage: g = L(lambda n: 0 if n < 50 else 1, valuation=2) sage: g.is_nonzero() # checks up to degree 22 = 2 + 20 False sage: g.is_nonzero() # checks up to degree 42 = 22 + 20 False sage: g.is_nonzero() # checks up to degree 62 = 42 + 20 True sage: L.options._reset()
>>> from sage.all import * >>> L.options.halting_precision = Integer(20) >>> f = L(lambda n: Integer(0), valuation=Integer(0)) >>> f.is_zero() True >>> g = L(lambda n: Integer(0) if n < Integer(50) else Integer(1), valuation=Integer(2)) >>> g.is_nonzero() # checks up to degree 22 = 2 + 20 False >>> g.is_nonzero() # checks up to degree 42 = 22 + 20 False >>> g.is_nonzero() # checks up to degree 62 = 42 + 20 True >>> L.options._reset()
L.options.halting_precision = 20 f = L(lambda n: 0, valuation=0) f.is_zero() g = L(lambda n: 0 if n < 50 else 1, valuation=2) g.is_nonzero() # checks up to degree 22 = 2 + 20 g.is_nonzero() # checks up to degree 42 = 22 + 20 g.is_nonzero() # checks up to degree 62 = 42 + 20 L.options._reset()
With a proof:
sage: L.<z> = LazyLaurentSeriesRing(GF(5)) sage: g = L(lambda n: 5 if n < 50 else 1, valuation=2) sage: g.is_nonzero(proof=True) (True, 50) sage: L.zero().is_nonzero(proof=True) (False, None)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(GF(Integer(5)), names=('z',)); (z,) = L._first_ngens(1) >>> g = L(lambda n: Integer(5) if n < Integer(50) else Integer(1), valuation=Integer(2)) >>> g.is_nonzero(proof=True) (True, 50) >>> L.zero().is_nonzero(proof=True) (False, None)
L.<z> = LazyLaurentSeriesRing(GF(5)) g = L(lambda n: 5 if n < 50 else 1, valuation=2) g.is_nonzero(proof=True) L.zero().is_nonzero(proof=True)
- is_trivial_zero()[source]¶
Return whether
selfis known to be trivially zero.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: f = L(lambda n: 0, valuation=2) sage: f.is_trivial_zero() False sage: L.zero().is_trivial_zero() True
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> f = L(lambda n: Integer(0), valuation=Integer(2)) >>> f.is_trivial_zero() False >>> L.zero().is_trivial_zero() True
L.<z> = LazyLaurentSeriesRing(ZZ) f = L(lambda n: 0, valuation=2) f.is_trivial_zero() L.zero().is_trivial_zero()
- lift_to_precision(absprec=None)[source]¶
Return another element of the same parent with absolute precision at least
absprec, congruent to this element modulo the precision of this element.Since the precision of a lazy series is infinity, this method returns the series itself, and the argument is ignored.
EXAMPLES:
sage: P.<t> = PowerSeriesRing(QQ, default_prec=2) sage: R.<z> = LazyPowerSeriesRing(P) sage: f = R(lambda n: 1/(1-t)^n) sage: f 1 + ((1+t+O(t^2))*z) + ((1+2*t+O(t^2))*z^2) + ((1+3*t+O(t^2))*z^3) + ((1+4*t+O(t^2))*z^4) + ((1+5*t+O(t^2))*z^5) + ((1+6*t+O(t^2))*z^6) + O(z^7) sage: f.lift_to_precision() 1 + ((1+t+O(t^2))*z) + ((1+2*t+O(t^2))*z^2) + ((1+3*t+O(t^2))*z^3) + ((1+4*t+O(t^2))*z^4) + ((1+5*t+O(t^2))*z^5) + ((1+6*t+O(t^2))*z^6) + O(z^7)
>>> from sage.all import * >>> P = PowerSeriesRing(QQ, default_prec=Integer(2), names=('t',)); (t,) = P._first_ngens(1) >>> R = LazyPowerSeriesRing(P, names=('z',)); (z,) = R._first_ngens(1) >>> f = R(lambda n: Integer(1)/(Integer(1)-t)**n) >>> f 1 + ((1+t+O(t^2))*z) + ((1+2*t+O(t^2))*z^2) + ((1+3*t+O(t^2))*z^3) + ((1+4*t+O(t^2))*z^4) + ((1+5*t+O(t^2))*z^5) + ((1+6*t+O(t^2))*z^6) + O(z^7) >>> f.lift_to_precision() 1 + ((1+t+O(t^2))*z) + ((1+2*t+O(t^2))*z^2) + ((1+3*t+O(t^2))*z^3) + ((1+4*t+O(t^2))*z^4) + ((1+5*t+O(t^2))*z^5) + ((1+6*t+O(t^2))*z^6) + O(z^7)
P.<t> = PowerSeriesRing(QQ, default_prec=2) R.<z> = LazyPowerSeriesRing(P) f = R(lambda n: 1/(1-t)^n) f f.lift_to_precision()
- log()[source]¶
Return the series for the natural logarithm of
self.EXAMPLES:
sage: L = LazyDirichletSeriesRing(QQ, "s") sage: Z = L(constant=1) sage: log(Z) # needs sage.symbolic 1/(2^s) + 1/(3^s) + 1/2/4^s + 1/(5^s) + 1/(7^s) + O(1/(8^s))
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(QQ, "s") >>> Z = L(constant=Integer(1)) >>> log(Z) # needs sage.symbolic 1/(2^s) + 1/(3^s) + 1/2/4^s + 1/(5^s) + 1/(7^s) + O(1/(8^s))
L = LazyDirichletSeriesRing(QQ, "s") Z = L(constant=1) log(Z) # needs sage.symbolic
- map_coefficients(f)[source]¶
Return the series with
fapplied to each nonzero coefficient ofself.INPUT:
func– function that takes in a coefficient and returns a new coefficient
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: m = L(lambda n: n, valuation=0); m z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) sage: m.map_coefficients(lambda c: c + 1) 2*z + 3*z^2 + 4*z^3 + 5*z^4 + 6*z^5 + 7*z^6 + 8*z^7 + O(z^8)
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> m = L(lambda n: n, valuation=Integer(0)); m z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) >>> m.map_coefficients(lambda c: c + Integer(1)) 2*z + 3*z^2 + 4*z^3 + 5*z^4 + 6*z^5 + 7*z^6 + 8*z^7 + O(z^8)
L.<z> = LazyLaurentSeriesRing(ZZ) m = L(lambda n: n, valuation=0); m m.map_coefficients(lambda c: c + 1)
Similarly for Dirichlet series:
sage: L = LazyDirichletSeriesRing(ZZ, "z") sage: s = L(lambda n: n-1) sage: s # needs sage.symbolic 1/(2^z) + 2/3^z + 3/4^z + 4/5^z + 5/6^z + 6/7^z + O(1/(8^z)) sage: ms = s.map_coefficients(lambda c: c + 1) # needs sage.symbolic sage: ms # needs sage.symbolic 2/2^z + 3/3^z + 4/4^z + 5/5^z + 6/6^z + 7/7^z + 8/8^z + O(1/(9^z))
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(ZZ, "z") >>> s = L(lambda n: n-Integer(1)) >>> s # needs sage.symbolic 1/(2^z) + 2/3^z + 3/4^z + 4/5^z + 5/6^z + 6/7^z + O(1/(8^z)) >>> ms = s.map_coefficients(lambda c: c + Integer(1)) # needs sage.symbolic >>> ms # needs sage.symbolic 2/2^z + 3/3^z + 4/4^z + 5/5^z + 6/6^z + 7/7^z + 8/8^z + O(1/(9^z))
L = LazyDirichletSeriesRing(ZZ, "z") s = L(lambda n: n-1) s # needs sage.symbolic ms = s.map_coefficients(lambda c: c + 1) # needs sage.symbolic ms # needs sage.symbolic
Similarly for multivariate power series:
sage: L.<x, y> = LazyPowerSeriesRing(QQ) sage: f = 1/(1-(x+y)); f 1 + (x+y) + (x^2+2*x*y+y^2) + (x^3+3*x^2*y+3*x*y^2+y^3) + (x^4+4*x^3*y+6*x^2*y^2+4*x*y^3+y^4) + (x^5+5*x^4*y+10*x^3*y^2+10*x^2*y^3+5*x*y^4+y^5) + (x^6+6*x^5*y+15*x^4*y^2+20*x^3*y^3+15*x^2*y^4+6*x*y^5+y^6) + O(x,y)^7 sage: f.map_coefficients(lambda c: c^2) 1 + (x+y) + (x^2+4*x*y+y^2) + (x^3+9*x^2*y+9*x*y^2+y^3) + (x^4+16*x^3*y+36*x^2*y^2+16*x*y^3+y^4) + (x^5+25*x^4*y+100*x^3*y^2+100*x^2*y^3+25*x*y^4+y^5) + (x^6+36*x^5*y+225*x^4*y^2+400*x^3*y^3+225*x^2*y^4+36*x*y^5+y^6) + O(x,y)^7
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> f = Integer(1)/(Integer(1)-(x+y)); f 1 + (x+y) + (x^2+2*x*y+y^2) + (x^3+3*x^2*y+3*x*y^2+y^3) + (x^4+4*x^3*y+6*x^2*y^2+4*x*y^3+y^4) + (x^5+5*x^4*y+10*x^3*y^2+10*x^2*y^3+5*x*y^4+y^5) + (x^6+6*x^5*y+15*x^4*y^2+20*x^3*y^3+15*x^2*y^4+6*x*y^5+y^6) + O(x,y)^7 >>> f.map_coefficients(lambda c: c**Integer(2)) 1 + (x+y) + (x^2+4*x*y+y^2) + (x^3+9*x^2*y+9*x*y^2+y^3) + (x^4+16*x^3*y+36*x^2*y^2+16*x*y^3+y^4) + (x^5+25*x^4*y+100*x^3*y^2+100*x^2*y^3+25*x*y^4+y^5) + (x^6+36*x^5*y+225*x^4*y^2+400*x^3*y^3+225*x^2*y^4+36*x*y^5+y^6) + O(x,y)^7
L.<x, y> = LazyPowerSeriesRing(QQ) f = 1/(1-(x+y)); f f.map_coefficients(lambda c: c^2)
Similarly for lazy symmetric functions:
sage: # needs sage.combinat sage: p = SymmetricFunctions(QQ).p() sage: L = LazySymmetricFunctions(p) sage: f = 1/(1-2*L(p[1])); f p[] + 2*p[1] + (4*p[1,1]) + (8*p[1,1,1]) + (16*p[1,1,1,1]) + (32*p[1,1,1,1,1]) + (64*p[1,1,1,1,1,1]) + O^7 sage: f.map_coefficients(lambda c: log(c, 2)) p[1] + (2*p[1,1]) + (3*p[1,1,1]) + (4*p[1,1,1,1]) + (5*p[1,1,1,1,1]) + (6*p[1,1,1,1,1,1]) + O^7
>>> from sage.all import * >>> # needs sage.combinat >>> p = SymmetricFunctions(QQ).p() >>> L = LazySymmetricFunctions(p) >>> f = Integer(1)/(Integer(1)-Integer(2)*L(p[Integer(1)])); f p[] + 2*p[1] + (4*p[1,1]) + (8*p[1,1,1]) + (16*p[1,1,1,1]) + (32*p[1,1,1,1,1]) + (64*p[1,1,1,1,1,1]) + O^7 >>> f.map_coefficients(lambda c: log(c, Integer(2))) p[1] + (2*p[1,1]) + (3*p[1,1,1]) + (4*p[1,1,1,1]) + (5*p[1,1,1,1,1]) + (6*p[1,1,1,1,1,1]) + O^7
# needs sage.combinat p = SymmetricFunctions(QQ).p() L = LazySymmetricFunctions(p) f = 1/(1-2*L(p[1])); f f.map_coefficients(lambda c: log(c, 2))
- prec()[source]¶
Return the precision of the series, which is infinity.
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: f = 1/(1 - z) sage: f.prec() +Infinity
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> f = Integer(1)/(Integer(1) - z) >>> f.prec() +Infinity
L.<z> = LazyLaurentSeriesRing(ZZ) f = 1/(1 - z) f.prec()
- q_pochhammer(q=None)[source]¶
Return the infinite
q-Pochhammer symbol \((a; q)_{\infty}\), where \(a\) isself.This is also one version of the quantum dilogarithm or the \(q\)-Exponential function.
INPUT:
q– (default: \(q \in \QQ(q)\)) the parameter \(q\)
EXAMPLES:
sage: q = ZZ['q'].fraction_field().gen() sage: L.<z> = LazyLaurentSeriesRing(q.parent()) sage: qp = L.q_pochhammer(q) sage: (z + z^2).q_pochhammer(q) - qp(z + z^2) O(z^7)
>>> from sage.all import * >>> q = ZZ['q'].fraction_field().gen() >>> L = LazyLaurentSeriesRing(q.parent(), names=('z',)); (z,) = L._first_ngens(1) >>> qp = L.q_pochhammer(q) >>> (z + z**Integer(2)).q_pochhammer(q) - qp(z + z**Integer(2)) O(z^7)
q = ZZ['q'].fraction_field().gen() L.<z> = LazyLaurentSeriesRing(q.parent()) qp = L.q_pochhammer(q) (z + z^2).q_pochhammer(q) - qp(z + z^2)
- sec()[source]¶
Return the secant of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: sec(z) 1 + 1/2*z^2 + 5/24*z^4 + 61/720*z^6 + O(z^7) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: sec(x/(1-y)).polynomial(4) 5/24*x^4 + 3/2*x^2*y^2 + x^2*y + 1/2*x^2 + 1
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> sec(z) 1 + 1/2*z^2 + 5/24*z^4 + 61/720*z^6 + O(z^7) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> sec(x/(Integer(1)-y)).polynomial(Integer(4)) 5/24*x^4 + 3/2*x^2*y^2 + x^2*y + 1/2*x^2 + 1
L.<z> = LazyLaurentSeriesRing(QQ) sec(z) L.<x,y> = LazyPowerSeriesRing(QQ) sec(x/(1-y)).polynomial(4)
- sech()[source]¶
Return the hyperbolic secant of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: sech(z) # needs sage.libs.flint 1 - 1/2*z^2 + 5/24*z^4 - 61/720*z^6 + O(z^7) sage: L.<x, y> = LazyPowerSeriesRing(QQ) sage: sech(x/(1-y)) # needs sage.libs.flint 1 + (-1/2*x^2) + (-x^2*y) + (5/24*x^4-3/2*x^2*y^2) + (5/6*x^4*y-2*x^2*y^3) + (-61/720*x^6+25/12*x^4*y^2-5/2*x^2*y^4) + O(x,y)^7
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> sech(z) # needs sage.libs.flint 1 - 1/2*z^2 + 5/24*z^4 - 61/720*z^6 + O(z^7) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> sech(x/(Integer(1)-y)) # needs sage.libs.flint 1 + (-1/2*x^2) + (-x^2*y) + (5/24*x^4-3/2*x^2*y^2) + (5/6*x^4*y-2*x^2*y^3) + (-61/720*x^6+25/12*x^4*y^2-5/2*x^2*y^4) + O(x,y)^7
L.<z> = LazyLaurentSeriesRing(QQ) sech(z) # needs sage.libs.flint L.<x, y> = LazyPowerSeriesRing(QQ) sech(x/(1-y)) # needs sage.libs.flint
- set(s)[source]¶
Define an equation by
self = s.INPUT:
s– a lazy series
EXAMPLES:
We begin by constructing the Catalan numbers:
sage: L.<z> = LazyPowerSeriesRing(ZZ) sage: C = L.undefined() sage: C.define(1 + z*C^2) sage: C 1 + z + 2*z^2 + 5*z^3 + 14*z^4 + 42*z^5 + 132*z^6 + O(z^7) sage: binomial(2000, 1000) / C[1000] # needs sage.symbolic 1001
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> C = L.undefined() >>> C.define(Integer(1) + z*C**Integer(2)) >>> C 1 + z + 2*z^2 + 5*z^3 + 14*z^4 + 42*z^5 + 132*z^6 + O(z^7) >>> binomial(Integer(2000), Integer(1000)) / C[Integer(1000)] # needs sage.symbolic 1001
L.<z> = LazyPowerSeriesRing(ZZ) C = L.undefined() C.define(1 + z*C^2) C binomial(2000, 1000) / C[1000] # needs sage.symbolic
The Catalan numbers but with a valuation \(1\):
sage: B = L.undefined(valuation=1) sage: B.define(z + B^2) sage: B z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8)
>>> from sage.all import * >>> B = L.undefined(valuation=Integer(1)) >>> B.define(z + B**Integer(2)) >>> B z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8)
B = L.undefined(valuation=1) B.define(z + B^2) B
We can define multiple series that are linked:
sage: s = L.undefined() sage: t = L.undefined() sage: s.define(1 + z*t^3) sage: t.define(1 + z*s^2) sage: s[0:9] [1, 1, 3, 9, 34, 132, 546, 2327, 10191] sage: t[0:9] [1, 1, 2, 7, 24, 95, 386, 1641, 7150]
>>> from sage.all import * >>> s = L.undefined() >>> t = L.undefined() >>> s.define(Integer(1) + z*t**Integer(3)) >>> t.define(Integer(1) + z*s**Integer(2)) >>> s[Integer(0):Integer(9)] [1, 1, 3, 9, 34, 132, 546, 2327, 10191] >>> t[Integer(0):Integer(9)] [1, 1, 2, 7, 24, 95, 386, 1641, 7150]
s = L.undefined() t = L.undefined() s.define(1 + z*t^3) t.define(1 + z*s^2) s[0:9] t[0:9]
A bigger example:
sage: L.<z> = LazyPowerSeriesRing(ZZ) sage: A = L.undefined(valuation=5) sage: B = L.undefined() sage: C = L.undefined(valuation=2) sage: A.define(z^5 + B^2) sage: B.define(z^5 + C^2) sage: C.define(z^2 + C^2 + A^2) sage: A[0:15] [0, 0, 0, 0, 0, 1, 0, 0, 1, 2, 5, 4, 14, 10, 48] sage: B[0:15] [0, 0, 0, 0, 1, 1, 2, 0, 5, 0, 14, 0, 44, 0, 138] sage: C[0:15] [0, 0, 1, 0, 1, 0, 2, 0, 5, 0, 15, 0, 44, 2, 142]
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> A = L.undefined(valuation=Integer(5)) >>> B = L.undefined() >>> C = L.undefined(valuation=Integer(2)) >>> A.define(z**Integer(5) + B**Integer(2)) >>> B.define(z**Integer(5) + C**Integer(2)) >>> C.define(z**Integer(2) + C**Integer(2) + A**Integer(2)) >>> A[Integer(0):Integer(15)] [0, 0, 0, 0, 0, 1, 0, 0, 1, 2, 5, 4, 14, 10, 48] >>> B[Integer(0):Integer(15)] [0, 0, 0, 0, 1, 1, 2, 0, 5, 0, 14, 0, 44, 0, 138] >>> C[Integer(0):Integer(15)] [0, 0, 1, 0, 1, 0, 2, 0, 5, 0, 15, 0, 44, 2, 142]
L.<z> = LazyPowerSeriesRing(ZZ) A = L.undefined(valuation=5) B = L.undefined() C = L.undefined(valuation=2) A.define(z^5 + B^2) B.define(z^5 + C^2) C.define(z^2 + C^2 + A^2) A[0:15] B[0:15] C[0:15]
Counting binary trees:
sage: L.<z> = LazyPowerSeriesRing(QQ) sage: s = L.undefined(valuation=1) sage: s.define(z + (s^2+s(z^2))/2) sage: s[0:9] [0, 1, 1, 1, 2, 3, 6, 11, 23]
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> s = L.undefined(valuation=Integer(1)) >>> s.define(z + (s**Integer(2)+s(z**Integer(2)))/Integer(2)) >>> s[Integer(0):Integer(9)] [0, 1, 1, 1, 2, 3, 6, 11, 23]
L.<z> = LazyPowerSeriesRing(QQ) s = L.undefined(valuation=1) s.define(z + (s^2+s(z^2))/2) s[0:9]
The \(q\)-Catalan numbers:
sage: R.<q> = ZZ[] sage: L.<z> = LazyLaurentSeriesRing(R) sage: s = L.undefined(valuation=0) sage: s.define(1+z*s*s(q*z)) sage: s 1 + z + (q + 1)*z^2 + (q^3 + q^2 + 2*q + 1)*z^3 + (q^6 + q^5 + 2*q^4 + 3*q^3 + 3*q^2 + 3*q + 1)*z^4 + (q^10 + q^9 + 2*q^8 + 3*q^7 + 5*q^6 + 5*q^5 + 7*q^4 + 7*q^3 + 6*q^2 + 4*q + 1)*z^5 + (q^15 + q^14 + 2*q^13 + 3*q^12 + 5*q^11 + 7*q^10 + 9*q^9 + 11*q^8 + 14*q^7 + 16*q^6 + 16*q^5 + 17*q^4 + 14*q^3 + 10*q^2 + 5*q + 1)*z^6 + O(z^7)
>>> from sage.all import * >>> R = ZZ['q']; (q,) = R._first_ngens(1) >>> L = LazyLaurentSeriesRing(R, names=('z',)); (z,) = L._first_ngens(1) >>> s = L.undefined(valuation=Integer(0)) >>> s.define(Integer(1)+z*s*s(q*z)) >>> s 1 + z + (q + 1)*z^2 + (q^3 + q^2 + 2*q + 1)*z^3 + (q^6 + q^5 + 2*q^4 + 3*q^3 + 3*q^2 + 3*q + 1)*z^4 + (q^10 + q^9 + 2*q^8 + 3*q^7 + 5*q^6 + 5*q^5 + 7*q^4 + 7*q^3 + 6*q^2 + 4*q + 1)*z^5 + (q^15 + q^14 + 2*q^13 + 3*q^12 + 5*q^11 + 7*q^10 + 9*q^9 + 11*q^8 + 14*q^7 + 16*q^6 + 16*q^5 + 17*q^4 + 14*q^3 + 10*q^2 + 5*q + 1)*z^6 + O(z^7)
R.<q> = ZZ[] L.<z> = LazyLaurentSeriesRing(R) s = L.undefined(valuation=0) s.define(1+z*s*s(q*z)) s
We count unlabeled ordered trees by total number of nodes and number of internal nodes:
sage: R.<q> = QQ[] sage: Q.<z> = LazyPowerSeriesRing(R) sage: leaf = z sage: internal_node = q * z sage: L = Q(constant=1, degree=1) sage: T = Q.undefined(valuation=1) sage: T.define(leaf + internal_node * L(T)) sage: T[0:6] [0, 1, q, q^2 + q, q^3 + 3*q^2 + q, q^4 + 6*q^3 + 6*q^2 + q]
>>> from sage.all import * >>> R = QQ['q']; (q,) = R._first_ngens(1) >>> Q = LazyPowerSeriesRing(R, names=('z',)); (z,) = Q._first_ngens(1) >>> leaf = z >>> internal_node = q * z >>> L = Q(constant=Integer(1), degree=Integer(1)) >>> T = Q.undefined(valuation=Integer(1)) >>> T.define(leaf + internal_node * L(T)) >>> T[Integer(0):Integer(6)] [0, 1, q, q^2 + q, q^3 + 3*q^2 + q, q^4 + 6*q^3 + 6*q^2 + q]
R.<q> = QQ[] Q.<z> = LazyPowerSeriesRing(R) leaf = z internal_node = q * z L = Q(constant=1, degree=1) T = Q.undefined(valuation=1) T.define(leaf + internal_node * L(T)) T[0:6]
Similarly for Dirichlet series:
sage: L = LazyDirichletSeriesRing(ZZ, "z") sage: g = L(constant=1, valuation=2) sage: F = L.undefined() sage: F.define(1 + g*F) sage: F[:16] [1, 1, 1, 2, 1, 3, 1, 4, 2, 3, 1, 8, 1, 3, 3] sage: oeis(_) # optional - internet 0: A002033: Number of perfect partitions of n. 1: A074206: Kalmár's [Kalmar's] problem: number of ordered factorizations of n. ... sage: F = L.undefined() sage: F.define(1 + g*F*F) sage: F[:16] [1, 1, 1, 3, 1, 5, 1, 10, 3, 5, 1, 24, 1, 5, 5]
>>> from sage.all import * >>> L = LazyDirichletSeriesRing(ZZ, "z") >>> g = L(constant=Integer(1), valuation=Integer(2)) >>> F = L.undefined() >>> F.define(Integer(1) + g*F) >>> F[:Integer(16)] [1, 1, 1, 2, 1, 3, 1, 4, 2, 3, 1, 8, 1, 3, 3] >>> oeis(_) # optional - internet 0: A002033: Number of perfect partitions of n. 1: A074206: Kalmár's [Kalmar's] problem: number of ordered factorizations of n. ... >>> F = L.undefined() >>> F.define(Integer(1) + g*F*F) >>> F[:Integer(16)] [1, 1, 1, 3, 1, 5, 1, 10, 3, 5, 1, 24, 1, 5, 5]
L = LazyDirichletSeriesRing(ZZ, "z") g = L(constant=1, valuation=2) F = L.undefined() F.define(1 + g*F) F[:16] oeis(_) # optional - internet F = L.undefined() F.define(1 + g*F*F) F[:16]
We can compute the Frobenius character of unlabeled trees:
sage: # needs sage.combinat sage: m = SymmetricFunctions(QQ).m() sage: s = SymmetricFunctions(QQ).s() sage: L = LazySymmetricFunctions(m) sage: E = L(lambda n: s[n], valuation=0) sage: X = L(s[1]) sage: A = L.undefined() sage: A.define(X*E(A)) sage: A[:6] [m[1], 2*m[1, 1] + m[2], 9*m[1, 1, 1] + 5*m[2, 1] + 2*m[3], 64*m[1, 1, 1, 1] + 34*m[2, 1, 1] + 18*m[2, 2] + 13*m[3, 1] + 4*m[4], 625*m[1, 1, 1, 1, 1] + 326*m[2, 1, 1, 1] + 171*m[2, 2, 1] + 119*m[3, 1, 1] + 63*m[3, 2] + 35*m[4, 1] + 9*m[5]]
>>> from sage.all import * >>> # needs sage.combinat >>> m = SymmetricFunctions(QQ).m() >>> s = SymmetricFunctions(QQ).s() >>> L = LazySymmetricFunctions(m) >>> E = L(lambda n: s[n], valuation=Integer(0)) >>> X = L(s[Integer(1)]) >>> A = L.undefined() >>> A.define(X*E(A)) >>> A[:Integer(6)] [m[1], 2*m[1, 1] + m[2], 9*m[1, 1, 1] + 5*m[2, 1] + 2*m[3], 64*m[1, 1, 1, 1] + 34*m[2, 1, 1] + 18*m[2, 2] + 13*m[3, 1] + 4*m[4], 625*m[1, 1, 1, 1, 1] + 326*m[2, 1, 1, 1] + 171*m[2, 2, 1] + 119*m[3, 1, 1] + 63*m[3, 2] + 35*m[4, 1] + 9*m[5]]
# needs sage.combinat m = SymmetricFunctions(QQ).m() s = SymmetricFunctions(QQ).s() L = LazySymmetricFunctions(m) E = L(lambda n: s[n], valuation=0) X = L(s[1]) A = L.undefined() A.define(X*E(A)) A[:6]
- shift(n)[source]¶
Return
selfwith the indices shifted byn.For example, a Laurent series is multiplied by the power \(z^n\), where \(z\) is the variable of
self. For series with a fixed minimal valuation (e.g., power series), this removes any terms that are less than the minimal valuation.INPUT:
n– the amount to shift
EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(ZZ) sage: f = 1 / (1 + 2*z) sage: f 1 - 2*z + 4*z^2 - 8*z^3 + 16*z^4 - 32*z^5 + 64*z^6 + O(z^7) sage: f.shift(3) z^3 - 2*z^4 + 4*z^5 - 8*z^6 + 16*z^7 - 32*z^8 + 64*z^9 + O(z^10) sage: f << -3 # shorthand z^-3 - 2*z^-2 + 4*z^-1 - 8 + 16*z - 32*z^2 + 64*z^3 + O(z^4) sage: g = z^-3 + 3 + z^2 sage: g.shift(5) z^2 + 3*z^5 + z^7 sage: L([2,0,3], valuation=2, degree=7, constant=1) << -2 2 + 3*z^2 + z^5 + z^6 + z^7 + O(z^8) sage: D = LazyDirichletSeriesRing(QQ, 't') sage: f = D([0,1,2]) sage: f # needs sage.symbolic 1/(2^t) + 2/3^t sage: sf = f.shift(3) sage: sf # needs sage.symbolic 1/(5^t) + 2/6^t
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> f = Integer(1) / (Integer(1) + Integer(2)*z) >>> f 1 - 2*z + 4*z^2 - 8*z^3 + 16*z^4 - 32*z^5 + 64*z^6 + O(z^7) >>> f.shift(Integer(3)) z^3 - 2*z^4 + 4*z^5 - 8*z^6 + 16*z^7 - 32*z^8 + 64*z^9 + O(z^10) >>> f << -Integer(3) # shorthand z^-3 - 2*z^-2 + 4*z^-1 - 8 + 16*z - 32*z^2 + 64*z^3 + O(z^4) >>> g = z**-Integer(3) + Integer(3) + z**Integer(2) >>> g.shift(Integer(5)) z^2 + 3*z^5 + z^7 >>> L([Integer(2),Integer(0),Integer(3)], valuation=Integer(2), degree=Integer(7), constant=Integer(1)) << -Integer(2) 2 + 3*z^2 + z^5 + z^6 + z^7 + O(z^8) >>> D = LazyDirichletSeriesRing(QQ, 't') >>> f = D([Integer(0),Integer(1),Integer(2)]) >>> f # needs sage.symbolic 1/(2^t) + 2/3^t >>> sf = f.shift(Integer(3)) >>> sf # needs sage.symbolic 1/(5^t) + 2/6^t
L.<z> = LazyLaurentSeriesRing(ZZ) f = 1 / (1 + 2*z) f f.shift(3) f << -3 # shorthand g = z^-3 + 3 + z^2 g.shift(5) L([2,0,3], valuation=2, degree=7, constant=1) << -2 D = LazyDirichletSeriesRing(QQ, 't') f = D([0,1,2]) f # needs sage.symbolic sf = f.shift(3) sf # needs sage.symbolic
Examples with power series (where the minimal valuation is \(0\)):
sage: L.<x> = LazyPowerSeriesRing(QQ) sage: f = 1 / (1 - x) sage: f.shift(2) x^2 + x^3 + x^4 + O(x^5) sage: g = f.shift(-1); g 1 + x + x^2 + O(x^3) sage: f == g True sage: g[-1] 0 sage: h = L(lambda n: 1) sage: LazyPowerSeriesRing.options.halting_precision(20) # verify up to degree 20 sage: f == h True sage: h == f True sage: h.shift(-1) == h True sage: LazyPowerSeriesRing.options._reset() sage: fp = L([3,3,3], constant=1) sage: fp.shift(2) 3*x^2 + 3*x^3 + 3*x^4 + x^5 + x^6 + x^7 + O(x^8) sage: fp.shift(-2) 3 + x + x^2 + x^3 + O(x^4) sage: fp.shift(-7) 1 + x + x^2 + O(x^3) sage: fp.shift(-5) == g True
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x',)); (x,) = L._first_ngens(1) >>> f = Integer(1) / (Integer(1) - x) >>> f.shift(Integer(2)) x^2 + x^3 + x^4 + O(x^5) >>> g = f.shift(-Integer(1)); g 1 + x + x^2 + O(x^3) >>> f == g True >>> g[-Integer(1)] 0 >>> h = L(lambda n: Integer(1)) >>> LazyPowerSeriesRing.options.halting_precision(Integer(20)) # verify up to degree 20 >>> f == h True >>> h == f True >>> h.shift(-Integer(1)) == h True >>> LazyPowerSeriesRing.options._reset() >>> fp = L([Integer(3),Integer(3),Integer(3)], constant=Integer(1)) >>> fp.shift(Integer(2)) 3*x^2 + 3*x^3 + 3*x^4 + x^5 + x^6 + x^7 + O(x^8) >>> fp.shift(-Integer(2)) 3 + x + x^2 + x^3 + O(x^4) >>> fp.shift(-Integer(7)) 1 + x + x^2 + O(x^3) >>> fp.shift(-Integer(5)) == g True
L.<x> = LazyPowerSeriesRing(QQ) f = 1 / (1 - x) f.shift(2) g = f.shift(-1); g f == g g[-1] h = L(lambda n: 1) LazyPowerSeriesRing.options.halting_precision(20) # verify up to degree 20 f == h h == f h.shift(-1) == h LazyPowerSeriesRing.options._reset() fp = L([3,3,3], constant=1) fp.shift(2) fp.shift(-2) fp.shift(-7) fp.shift(-5) == g
We compare the shifting with converting to the fraction field (see also Issue #35293):
sage: M = L.fraction_field() sage: f = L([1,2,3,4]); f 1 + 2*x + 3*x^2 + 4*x^3 sage: f.shift(-3) 4 sage: M(f).shift(-3) x^-3 + 2*x^-2 + 3*x^-1 + 4
>>> from sage.all import * >>> M = L.fraction_field() >>> f = L([Integer(1),Integer(2),Integer(3),Integer(4)]); f 1 + 2*x + 3*x^2 + 4*x^3 >>> f.shift(-Integer(3)) 4 >>> M(f).shift(-Integer(3)) x^-3 + 2*x^-2 + 3*x^-1 + 4
M = L.fraction_field() f = L([1,2,3,4]); f f.shift(-3) M(f).shift(-3)
An example with a more general function:
sage: fun = lambda n: 1 if ZZ(n).is_power_of(2) else 0 sage: f = L(fun); f x + x^2 + x^4 + O(x^7) sage: fs = f.shift(-4) sage: fs 1 + x^4 + O(x^7) sage: fs.shift(4) x^4 + x^8 + O(x^11) sage: M(f).shift(-4) x^-3 + x^-2 + 1 + O(x^4)
>>> from sage.all import * >>> fun = lambda n: Integer(1) if ZZ(n).is_power_of(Integer(2)) else Integer(0) >>> f = L(fun); f x + x^2 + x^4 + O(x^7) >>> fs = f.shift(-Integer(4)) >>> fs 1 + x^4 + O(x^7) >>> fs.shift(Integer(4)) x^4 + x^8 + O(x^11) >>> M(f).shift(-Integer(4)) x^-3 + x^-2 + 1 + O(x^4)
fun = lambda n: 1 if ZZ(n).is_power_of(2) else 0 f = L(fun); f fs = f.shift(-4) fs fs.shift(4) M(f).shift(-4)
- sin()[source]¶
Return the sine of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: sin(z) z - 1/6*z^3 + 1/120*z^5 - 1/5040*z^7 + O(z^8) sage: sin(1 + z) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: sin(x/(1-y)).polynomial(3) -1/6*x^3 + x*y^2 + x*y + x
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> sin(z) z - 1/6*z^3 + 1/120*z^5 - 1/5040*z^7 + O(z^8) >>> sin(Integer(1) + z) Traceback (most recent call last): ... ValueError: can only compose with a positive valuation series >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> sin(x/(Integer(1)-y)).polynomial(Integer(3)) -1/6*x^3 + x*y^2 + x*y + x
L.<z> = LazyLaurentSeriesRing(QQ) sin(z) sin(1 + z) L.<x,y> = LazyPowerSeriesRing(QQ) sin(x/(1-y)).polynomial(3)
- sinh()[source]¶
Return the hyperbolic sine of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: sinh(z) z + 1/6*z^3 + 1/120*z^5 + 1/5040*z^7 + O(z^8) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: sinh(x/(1-y)) x + x*y + (1/6*x^3+x*y^2) + (1/2*x^3*y+x*y^3) + (1/120*x^5+x^3*y^2+x*y^4) + (1/24*x^5*y+5/3*x^3*y^3+x*y^5) + (1/5040*x^7+1/8*x^5*y^2+5/2*x^3*y^4+x*y^6) + O(x,y)^8
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> sinh(z) z + 1/6*z^3 + 1/120*z^5 + 1/5040*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> sinh(x/(Integer(1)-y)) x + x*y + (1/6*x^3+x*y^2) + (1/2*x^3*y+x*y^3) + (1/120*x^5+x^3*y^2+x*y^4) + (1/24*x^5*y+5/3*x^3*y^3+x*y^5) + (1/5040*x^7+1/8*x^5*y^2+5/2*x^3*y^4+x*y^6) + O(x,y)^8
L.<z> = LazyLaurentSeriesRing(QQ) sinh(z) L.<x,y> = LazyPowerSeriesRing(QQ) sinh(x/(1-y))
- sqrt()[source]¶
Return
self^(1/2).EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: sqrt(1+z) 1 + 1/2*z - 1/8*z^2 + 1/16*z^3 - 5/128*z^4 + 7/256*z^5 - 21/1024*z^6 + O(z^7) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: sqrt(1+x/(1-y)) 1 + 1/2*x + (-1/8*x^2+1/2*x*y) + (1/16*x^3-1/4*x^2*y+1/2*x*y^2) + (-5/128*x^4+3/16*x^3*y-3/8*x^2*y^2+1/2*x*y^3) + (7/256*x^5-5/32*x^4*y+3/8*x^3*y^2-1/2*x^2*y^3+1/2*x*y^4) + (-21/1024*x^6+35/256*x^5*y-25/64*x^4*y^2+5/8*x^3*y^3-5/8*x^2*y^4+1/2*x*y^5) + O(x,y)^7
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> sqrt(Integer(1)+z) 1 + 1/2*z - 1/8*z^2 + 1/16*z^3 - 5/128*z^4 + 7/256*z^5 - 21/1024*z^6 + O(z^7) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> sqrt(Integer(1)+x/(Integer(1)-y)) 1 + 1/2*x + (-1/8*x^2+1/2*x*y) + (1/16*x^3-1/4*x^2*y+1/2*x*y^2) + (-5/128*x^4+3/16*x^3*y-3/8*x^2*y^2+1/2*x*y^3) + (7/256*x^5-5/32*x^4*y+3/8*x^3*y^2-1/2*x^2*y^3+1/2*x*y^4) + (-21/1024*x^6+35/256*x^5*y-25/64*x^4*y^2+5/8*x^3*y^3-5/8*x^2*y^4+1/2*x*y^5) + O(x,y)^7
L.<z> = LazyLaurentSeriesRing(QQ) sqrt(1+z) L.<x,y> = LazyPowerSeriesRing(QQ) sqrt(1+x/(1-y))
This also works for Dirichlet series:
sage: # needs sage.symbolic sage: D = LazyDirichletSeriesRing(SR, "s") sage: Z = D(constant=1) sage: f = sqrt(Z); f 1 + 1/2/2^s + 1/2/3^s + 3/8/4^s + 1/2/5^s + 1/4/6^s + 1/2/7^s + O(1/(8^s)) sage: f*f - Z O(1/(8^s))
>>> from sage.all import * >>> # needs sage.symbolic >>> D = LazyDirichletSeriesRing(SR, "s") >>> Z = D(constant=Integer(1)) >>> f = sqrt(Z); f 1 + 1/2/2^s + 1/2/3^s + 3/8/4^s + 1/2/5^s + 1/4/6^s + 1/2/7^s + O(1/(8^s)) >>> f*f - Z O(1/(8^s))
# needs sage.symbolic D = LazyDirichletSeriesRing(SR, "s") Z = D(constant=1) f = sqrt(Z); f f*f - Z
- tan()[source]¶
Return the tangent of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: tan(z) z + 1/3*z^3 + 2/15*z^5 + 17/315*z^7 + O(z^8) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: tan(x/(1-y)).polynomial(5) 2/15*x^5 + 2*x^3*y^2 + x*y^4 + x^3*y + x*y^3 + 1/3*x^3 + x*y^2 + x*y + x
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> tan(z) z + 1/3*z^3 + 2/15*z^5 + 17/315*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> tan(x/(Integer(1)-y)).polynomial(Integer(5)) 2/15*x^5 + 2*x^3*y^2 + x*y^4 + x^3*y + x*y^3 + 1/3*x^3 + x*y^2 + x*y + x
L.<z> = LazyLaurentSeriesRing(QQ) tan(z) L.<x,y> = LazyPowerSeriesRing(QQ) tan(x/(1-y)).polynomial(5)
- tanh()[source]¶
Return the hyperbolic tangent of
self.EXAMPLES:
sage: L.<z> = LazyLaurentSeriesRing(QQ) sage: tanh(z) # needs sage.libs.flint z - 1/3*z^3 + 2/15*z^5 - 17/315*z^7 + O(z^8) sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: tanh(x/(1-y)) # needs sage.libs.flint x + x*y + (-1/3*x^3+x*y^2) + (-x^3*y+x*y^3) + (2/15*x^5-2*x^3*y^2+x*y^4) + (2/3*x^5*y-10/3*x^3*y^3+x*y^5) + (-17/315*x^7+2*x^5*y^2-5*x^3*y^4+x*y^6) + O(x,y)^8
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> tanh(z) # needs sage.libs.flint z - 1/3*z^3 + 2/15*z^5 - 17/315*z^7 + O(z^8) >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> tanh(x/(Integer(1)-y)) # needs sage.libs.flint x + x*y + (-1/3*x^3+x*y^2) + (-x^3*y+x*y^3) + (2/15*x^5-2*x^3*y^2+x*y^4) + (2/3*x^5*y-10/3*x^3*y^3+x*y^5) + (-17/315*x^7+2*x^5*y^2-5*x^3*y^4+x*y^6) + O(x,y)^8
L.<z> = LazyLaurentSeriesRing(QQ) tanh(z) # needs sage.libs.flint L.<x,y> = LazyPowerSeriesRing(QQ) tanh(x/(1-y)) # needs sage.libs.flint
- truncate(d)[source]¶
Return the series obtained by removing all terms of degree at least
d.INPUT:
d– integer; the degree from which the series is truncated
EXAMPLES:
Dense implementation:
sage: L.<z> = LazyLaurentSeriesRing(ZZ, sparse=False) sage: alpha = 1/(1-z) sage: alpha 1 + z + z^2 + O(z^3) sage: beta = alpha.truncate(5) sage: beta 1 + z + z^2 + z^3 + z^4 sage: alpha - beta z^5 + z^6 + z^7 + O(z^8) sage: M = L(lambda n: n, valuation=0); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) sage: M.truncate(4) z + 2*z^2 + 3*z^3
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, sparse=False, names=('z',)); (z,) = L._first_ngens(1) >>> alpha = Integer(1)/(Integer(1)-z) >>> alpha 1 + z + z^2 + O(z^3) >>> beta = alpha.truncate(Integer(5)) >>> beta 1 + z + z^2 + z^3 + z^4 >>> alpha - beta z^5 + z^6 + z^7 + O(z^8) >>> M = L(lambda n: n, valuation=Integer(0)); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) >>> M.truncate(Integer(4)) z + 2*z^2 + 3*z^3
L.<z> = LazyLaurentSeriesRing(ZZ, sparse=False) alpha = 1/(1-z) alpha beta = alpha.truncate(5) beta alpha - beta M = L(lambda n: n, valuation=0); M M.truncate(4)
Sparse Implementation:
sage: L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) sage: M = L(lambda n: n, valuation=0); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) sage: M.truncate(4) z + 2*z^2 + 3*z^3
>>> from sage.all import * >>> L = LazyLaurentSeriesRing(ZZ, sparse=True, names=('z',)); (z,) = L._first_ngens(1) >>> M = L(lambda n: n, valuation=Integer(0)); M z + 2*z^2 + 3*z^3 + 4*z^4 + 5*z^5 + 6*z^6 + O(z^7) >>> M.truncate(Integer(4)) z + 2*z^2 + 3*z^3
L.<z> = LazyLaurentSeriesRing(ZZ, sparse=True) M = L(lambda n: n, valuation=0); M M.truncate(4)
Series which are known to be exact can also be truncated:
sage: M = z + z^2 + z^3 + z^4 sage: M.truncate(4) z + z^2 + z^3
>>> from sage.all import * >>> M = z + z**Integer(2) + z**Integer(3) + z**Integer(4) >>> M.truncate(Integer(4)) z + z^2 + z^3
M = z + z^2 + z^3 + z^4 M.truncate(4)
- class sage.rings.lazy_series.LazyPowerSeries(parent, coeff_stream)[source]¶
Bases:
LazyCauchyProductSeriesA Taylor series where the coefficients are computed lazily.
EXAMPLES:
sage: L.<x, y> = LazyPowerSeriesRing(ZZ) sage: f = 1 / (1 - x^2 + y^3); f 1 + x^2 + (-y^3) + x^4 + (-2*x^2*y^3) + (x^6+y^6) + O(x,y)^7 sage: P.<x, y> = PowerSeriesRing(ZZ, default_prec=101) sage: g = 1 / (1 - x^2 + y^3); f[100] - g[100] 0
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> f = Integer(1) / (Integer(1) - x**Integer(2) + y**Integer(3)); f 1 + x^2 + (-y^3) + x^4 + (-2*x^2*y^3) + (x^6+y^6) + O(x,y)^7 >>> P = PowerSeriesRing(ZZ, default_prec=Integer(101), names=('x', 'y',)); (x, y,) = P._first_ngens(2) >>> g = Integer(1) / (Integer(1) - x**Integer(2) + y**Integer(3)); f[Integer(100)] - g[Integer(100)] 0
L.<x, y> = LazyPowerSeriesRing(ZZ) f = 1 / (1 - x^2 + y^3); f P.<x, y> = PowerSeriesRing(ZZ, default_prec=101) g = 1 / (1 - x^2 + y^3); f[100] - g[100]
Lazy Taylor series is picklable:
sage: g = loads(dumps(f)) sage: g 1 + x^2 + (-y^3) + x^4 + (-2*x^2*y^3) + (x^6+y^6) + O(x,y)^7 sage: g == f True
>>> from sage.all import * >>> g = loads(dumps(f)) >>> g 1 + x^2 + (-y^3) + x^4 + (-2*x^2*y^3) + (x^6+y^6) + O(x,y)^7 >>> g == f True
g = loads(dumps(f)) g g == f
- O(prec)[source]¶
Return the power series of precision at most
precobtained by adding \(O(q^\text{prec})\) to \(f\), where \(q\) is the (tuple of) variable(s).EXAMPLES:
sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: f = 1 / (1 - x + y) sage: f 1 + (x-y) + (x^2-2*x*y+y^2) + (x^3-3*x^2*y+3*x*y^2-y^3) + (x^4-4*x^3*y+6*x^2*y^2-4*x*y^3+y^4) + (x^5-5*x^4*y+10*x^3*y^2-10*x^2*y^3+5*x*y^4-y^5) + (x^6-6*x^5*y+15*x^4*y^2-20*x^3*y^3+15*x^2*y^4-6*x*y^5+y^6) + O(x,y)^7 sage: f3 = f.add_bigoh(3); f3 1 + x - y + x^2 - 2*x*y + y^2 + O(x, y)^3 sage: f3.parent() Multivariate Power Series Ring in x, y over Rational Field sage: R.<t> = QQ[] sage: L.<x> = LazyPowerSeriesRing(R) sage: f = 1 / (1 - t^3*x) sage: f 1 + t^3*x + t^6*x^2 + t^9*x^3 + t^12*x^4 + t^15*x^5 + t^18*x^6 + O(x^7) sage: f3 = f.add_bigoh(3); f3 1 + t^3*x + t^6*x^2 + O(x^3) sage: f3.parent() Power Series Ring in x over Univariate Polynomial Ring in t over Rational Field
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> f = Integer(1) / (Integer(1) - x + y) >>> f 1 + (x-y) + (x^2-2*x*y+y^2) + (x^3-3*x^2*y+3*x*y^2-y^3) + (x^4-4*x^3*y+6*x^2*y^2-4*x*y^3+y^4) + (x^5-5*x^4*y+10*x^3*y^2-10*x^2*y^3+5*x*y^4-y^5) + (x^6-6*x^5*y+15*x^4*y^2-20*x^3*y^3+15*x^2*y^4-6*x*y^5+y^6) + O(x,y)^7 >>> f3 = f.add_bigoh(Integer(3)); f3 1 + x - y + x^2 - 2*x*y + y^2 + O(x, y)^3 >>> f3.parent() Multivariate Power Series Ring in x, y over Rational Field >>> R = QQ['t']; (t,) = R._first_ngens(1) >>> L = LazyPowerSeriesRing(R, names=('x',)); (x,) = L._first_ngens(1) >>> f = Integer(1) / (Integer(1) - t**Integer(3)*x) >>> f 1 + t^3*x + t^6*x^2 + t^9*x^3 + t^12*x^4 + t^15*x^5 + t^18*x^6 + O(x^7) >>> f3 = f.add_bigoh(Integer(3)); f3 1 + t^3*x + t^6*x^2 + O(x^3) >>> f3.parent() Power Series Ring in x over Univariate Polynomial Ring in t over Rational Field
L.<x,y> = LazyPowerSeriesRing(QQ) f = 1 / (1 - x + y) f f3 = f.add_bigoh(3); f3 f3.parent() R.<t> = QQ[] L.<x> = LazyPowerSeriesRing(R) f = 1 / (1 - t^3*x) f f3 = f.add_bigoh(3); f3 f3.parent()
- adams_operator(p)[source]¶
Return the image of
selfunder the Adams operator of indexp.This raises all variables to the power
p, both the power series variables and the variables inside the coefficient ring.INPUT:
p– positive integer
EXAMPLES:
With no variables in the base ring:
sage: A = LazyPowerSeriesRing(QQ,'t') sage: f = A([1,2,3,4]); f 1 + 2*t + 3*t^2 + 4*t^3 sage: f.adams_operator(2) 1 + 2*t^2 + 3*t^4 + 4*t^6
>>> from sage.all import * >>> A = LazyPowerSeriesRing(QQ,'t') >>> f = A([Integer(1),Integer(2),Integer(3),Integer(4)]); f 1 + 2*t + 3*t^2 + 4*t^3 >>> f.adams_operator(Integer(2)) 1 + 2*t^2 + 3*t^4 + 4*t^6
A = LazyPowerSeriesRing(QQ,'t') f = A([1,2,3,4]); f f.adams_operator(2)
With variables in the base ring:
sage: q = polygen(QQ,'q') sage: A = LazyPowerSeriesRing(q.parent(),'t') sage: f = A([0,1+q,2,3+q**2]); f ((q+1)*t) + 2*t^2 + ((q^2+3)*t^3) sage: f.adams_operator(2) ((q^2+1)*t^2) + 2*t^4 + ((q^4+3)*t^6)
>>> from sage.all import * >>> q = polygen(QQ,'q') >>> A = LazyPowerSeriesRing(q.parent(),'t') >>> f = A([Integer(0),Integer(1)+q,Integer(2),Integer(3)+q**Integer(2)]); f ((q+1)*t) + 2*t^2 + ((q^2+3)*t^3) >>> f.adams_operator(Integer(2)) ((q^2+1)*t^2) + 2*t^4 + ((q^4+3)*t^6)
q = polygen(QQ,'q') A = LazyPowerSeriesRing(q.parent(),'t') f = A([0,1+q,2,3+q**2]); f f.adams_operator(2)
In the multivariate case:
sage: A = LazyPowerSeriesRing(ZZ,'t,u') sage: f = A({(1,2):4,(2,3):6}); f 4*t*u^2 + 6*t^2*u^3 sage: f.adams_operator(3) 4*t^3*u^6 + 6*t^6*u^9
>>> from sage.all import * >>> A = LazyPowerSeriesRing(ZZ,'t,u') >>> f = A({(Integer(1),Integer(2)):Integer(4),(Integer(2),Integer(3)):Integer(6)}); f 4*t*u^2 + 6*t^2*u^3 >>> f.adams_operator(Integer(3)) 4*t^3*u^6 + 6*t^6*u^9
A = LazyPowerSeriesRing(ZZ,'t,u') f = A({(1,2):4,(2,3):6}); f f.adams_operator(3)
- add_bigoh(prec)[source]¶
Return the power series of precision at most
precobtained by adding \(O(q^\text{prec})\) to \(f\), where \(q\) is the (tuple of) variable(s).EXAMPLES:
sage: L.<x,y> = LazyPowerSeriesRing(QQ) sage: f = 1 / (1 - x + y) sage: f 1 + (x-y) + (x^2-2*x*y+y^2) + (x^3-3*x^2*y+3*x*y^2-y^3) + (x^4-4*x^3*y+6*x^2*y^2-4*x*y^3+y^4) + (x^5-5*x^4*y+10*x^3*y^2-10*x^2*y^3+5*x*y^4-y^5) + (x^6-6*x^5*y+15*x^4*y^2-20*x^3*y^3+15*x^2*y^4-6*x*y^5+y^6) + O(x,y)^7 sage: f3 = f.add_bigoh(3); f3 1 + x - y + x^2 - 2*x*y + y^2 + O(x, y)^3 sage: f3.parent() Multivariate Power Series Ring in x, y over Rational Field sage: R.<t> = QQ[] sage: L.<x> = LazyPowerSeriesRing(R) sage: f = 1 / (1 - t^3*x) sage: f 1 + t^3*x + t^6*x^2 + t^9*x^3 + t^12*x^4 + t^15*x^5 + t^18*x^6 + O(x^7) sage: f3 = f.add_bigoh(3); f3 1 + t^3*x + t^6*x^2 + O(x^3) sage: f3.parent() Power Series Ring in x over Univariate Polynomial Ring in t over Rational Field
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> f = Integer(1) / (Integer(1) - x + y) >>> f 1 + (x-y) + (x^2-2*x*y+y^2) + (x^3-3*x^2*y+3*x*y^2-y^3) + (x^4-4*x^3*y+6*x^2*y^2-4*x*y^3+y^4) + (x^5-5*x^4*y+10*x^3*y^2-10*x^2*y^3+5*x*y^4-y^5) + (x^6-6*x^5*y+15*x^4*y^2-20*x^3*y^3+15*x^2*y^4-6*x*y^5+y^6) + O(x,y)^7 >>> f3 = f.add_bigoh(Integer(3)); f3 1 + x - y + x^2 - 2*x*y + y^2 + O(x, y)^3 >>> f3.parent() Multivariate Power Series Ring in x, y over Rational Field >>> R = QQ['t']; (t,) = R._first_ngens(1) >>> L = LazyPowerSeriesRing(R, names=('x',)); (x,) = L._first_ngens(1) >>> f = Integer(1) / (Integer(1) - t**Integer(3)*x) >>> f 1 + t^3*x + t^6*x^2 + t^9*x^3 + t^12*x^4 + t^15*x^5 + t^18*x^6 + O(x^7) >>> f3 = f.add_bigoh(Integer(3)); f3 1 + t^3*x + t^6*x^2 + O(x^3) >>> f3.parent() Power Series Ring in x over Univariate Polynomial Ring in t over Rational Field
L.<x,y> = LazyPowerSeriesRing(QQ) f = 1 / (1 - x + y) f f3 = f.add_bigoh(3); f3 f3.parent() R.<t> = QQ[] L.<x> = LazyPowerSeriesRing(R) f = 1 / (1 - t^3*x) f f3 = f.add_bigoh(3); f3 f3.parent()
- compose(*g)[source]¶
Return the composition of
selfwithg.The arity of
selfmust be equal to the number of arguments provided.Given a Taylor series \(f\) of arity \(n\) and a tuple of Taylor series \(g = (g_1,\dots, g_n)\) over the same base ring, the composition \(f \circ g\) is defined if and only if for each \(1\leq i\leq n\):
\(g_i\) is zero, or
setting all variables except the \(i\)-th in \(f\) to zero yields a polynomial, or
\(\mathrm{val}(g_i) > 0\).
If \(f\) is a univariate ‘exact’ series, we can check whether \(f\) is a actually a polynomial. However, if \(f\) is a multivariate series, we have no way to test whether setting all but one variable of \(f\) to zero yields a polynomial, except if \(f\) itself is ‘exact’ and therefore a polynomial.
INPUT:
g– other series, all can be coerced into the same parent
EXAMPLES:
sage: L.<x, y, z> = LazyPowerSeriesRing(QQ) sage: M.<a, b> = LazyPowerSeriesRing(ZZ) sage: g1 = 1 / (1 - x) sage: g2 = x + y^2 sage: p = a^2 + b + 1 sage: p(g1, g2) - g1^2 - g2 - 1 O(x,y,z)^7
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y', 'z',)); (x, y, z,) = L._first_ngens(3) >>> M = LazyPowerSeriesRing(ZZ, names=('a', 'b',)); (a, b,) = M._first_ngens(2) >>> g1 = Integer(1) / (Integer(1) - x) >>> g2 = x + y**Integer(2) >>> p = a**Integer(2) + b + Integer(1) >>> p(g1, g2) - g1**Integer(2) - g2 - Integer(1) O(x,y,z)^7
L.<x, y, z> = LazyPowerSeriesRing(QQ) M.<a, b> = LazyPowerSeriesRing(ZZ) g1 = 1 / (1 - x) g2 = x + y^2 p = a^2 + b + 1 p(g1, g2) - g1^2 - g2 - 1
The number of mappings from a set with \(m\) elements to a set with \(n\) elements:
sage: M.<a> = LazyPowerSeriesRing(QQ) sage: Ea = M(lambda n: 1/factorial(n)) sage: Ex = L(lambda n: 1/factorial(n)*x^n) sage: Ea(Ex*y)[5] 1/24*x^4*y + 2/3*x^3*y^2 + 3/4*x^2*y^3 + 1/6*x*y^4 + 1/120*y^5
>>> from sage.all import * >>> M = LazyPowerSeriesRing(QQ, names=('a',)); (a,) = M._first_ngens(1) >>> Ea = M(lambda n: Integer(1)/factorial(n)) >>> Ex = L(lambda n: Integer(1)/factorial(n)*x**n) >>> Ea(Ex*y)[Integer(5)] 1/24*x^4*y + 2/3*x^3*y^2 + 3/4*x^2*y^3 + 1/6*x*y^4 + 1/120*y^5
M.<a> = LazyPowerSeriesRing(QQ) Ea = M(lambda n: 1/factorial(n)) Ex = L(lambda n: 1/factorial(n)*x^n) Ea(Ex*y)[5]
So, there are \(3! 2! 2/3 = 8\) mappings from a three element set to a two element set.
We perform the composition with a lazy Laurent series:
sage: N.<w> = LazyLaurentSeriesRing(QQ) sage: f1 = 1 / (1 - w) sage: f2 = cot(w / (1 - w)) sage: p(f1, f2) w^-1 + 1 + 5/3*w + 8/3*w^2 + 164/45*w^3 + 23/5*w^4 + 5227/945*w^5 + O(w^6)
>>> from sage.all import * >>> N = LazyLaurentSeriesRing(QQ, names=('w',)); (w,) = N._first_ngens(1) >>> f1 = Integer(1) / (Integer(1) - w) >>> f2 = cot(w / (Integer(1) - w)) >>> p(f1, f2) w^-1 + 1 + 5/3*w + 8/3*w^2 + 164/45*w^3 + 23/5*w^4 + 5227/945*w^5 + O(w^6)
N.<w> = LazyLaurentSeriesRing(QQ) f1 = 1 / (1 - w) f2 = cot(w / (1 - w)) p(f1, f2)
We perform the composition with a lazy Dirichlet series:
sage: # needs sage.symbolic sage: D = LazyDirichletSeriesRing(QQ, "s") sage: g = D(constant=1)-1 sage: g 1/(2^s) + 1/(3^s) + 1/(4^s) + O(1/(5^s)) sage: f = 1 / (1 - x - y*z); f 1 + x + (x^2+y*z) + (x^3+2*x*y*z) + (x^4+3*x^2*y*z+y^2*z^2) + (x^5+4*x^3*y*z+3*x*y^2*z^2) + (x^6+5*x^4*y*z+6*x^2*y^2*z^2+y^3*z^3) + O(x,y,z)^7 sage: fog = f(g, g, g) sage: fog 1 + 1/(2^s) + 1/(3^s) + 3/4^s + 1/(5^s) + 5/6^s + O(1/(7^s)) sage: fg = 1 / (1 - g - g*g) sage: fg 1 + 1/(2^s) + 1/(3^s) + 3/4^s + 1/(5^s) + 5/6^s + 1/(7^s) + O(1/(8^s)) sage: fog - fg O(1/(8^s)) sage: f = 1 / (1 - 2*a) sage: f(g) # needs sage.symbolic 1 + 2/2^s + 2/3^s + 6/4^s + 2/5^s + 10/6^s + 2/7^s + O(1/(8^s)) sage: 1 / (1 - 2*g) # needs sage.symbolic 1 + 2/2^s + 2/3^s + 6/4^s + 2/5^s + 10/6^s + 2/7^s + O(1/(8^s))
>>> from sage.all import * >>> # needs sage.symbolic >>> D = LazyDirichletSeriesRing(QQ, "s") >>> g = D(constant=Integer(1))-Integer(1) >>> g 1/(2^s) + 1/(3^s) + 1/(4^s) + O(1/(5^s)) >>> f = Integer(1) / (Integer(1) - x - y*z); f 1 + x + (x^2+y*z) + (x^3+2*x*y*z) + (x^4+3*x^2*y*z+y^2*z^2) + (x^5+4*x^3*y*z+3*x*y^2*z^2) + (x^6+5*x^4*y*z+6*x^2*y^2*z^2+y^3*z^3) + O(x,y,z)^7 >>> fog = f(g, g, g) >>> fog 1 + 1/(2^s) + 1/(3^s) + 3/4^s + 1/(5^s) + 5/6^s + O(1/(7^s)) >>> fg = Integer(1) / (Integer(1) - g - g*g) >>> fg 1 + 1/(2^s) + 1/(3^s) + 3/4^s + 1/(5^s) + 5/6^s + 1/(7^s) + O(1/(8^s)) >>> fog - fg O(1/(8^s)) >>> f = Integer(1) / (Integer(1) - Integer(2)*a) >>> f(g) # needs sage.symbolic 1 + 2/2^s + 2/3^s + 6/4^s + 2/5^s + 10/6^s + 2/7^s + O(1/(8^s)) >>> Integer(1) / (Integer(1) - Integer(2)*g) # needs sage.symbolic 1 + 2/2^s + 2/3^s + 6/4^s + 2/5^s + 10/6^s + 2/7^s + O(1/(8^s))
# needs sage.symbolic D = LazyDirichletSeriesRing(QQ, "s") g = D(constant=1)-1 g f = 1 / (1 - x - y*z); f fog = f(g, g, g) fog fg = 1 / (1 - g - g*g) fg fog - fg f = 1 / (1 - 2*a) f(g) # needs sage.symbolic 1 / (1 - 2*g) # needs sage.symbolic
The output parent is always the common parent between the base ring of \(f\) and the parent of \(g\) or extended to the corresponding lazy series:
sage: T.<x,y> = LazyPowerSeriesRing(QQ) sage: R.<a,b,c> = ZZ[] sage: S.<v> = R[] sage: L.<z> = LaurentPolynomialRing(ZZ) sage: parent(x(a, b)) Multivariate Polynomial Ring in a, b, c over Rational Field sage: parent(x(CC(2), a)) Multivariate Polynomial Ring in a, b, c over Complex Field with 53 bits of precision sage: parent(x(0, 0)) Rational Field sage: f = 1 / (1 - x - y); f 1 + (x+y) + (x^2+2*x*y+y^2) + (x^3+3*x^2*y+3*x*y^2+y^3) + (x^4+4*x^3*y+6*x^2*y^2+4*x*y^3+y^4) + (x^5+5*x^4*y+10*x^3*y^2+10*x^2*y^3+5*x*y^4+y^5) + (x^6+6*x^5*y+15*x^4*y^2+20*x^3*y^3+15*x^2*y^4+6*x*y^5+y^6) + O(x,y)^7 sage: f(a^2, b*c) 1 + (a^2+b*c) + (a^4+2*a^2*b*c+b^2*c^2) + (a^6+3*a^4*b*c+3*a^2*b^2*c^2+b^3*c^3) + O(a,b,c)^7 sage: f(v, v^2) 1 + v + 2*v^2 + 3*v^3 + 5*v^4 + 8*v^5 + 13*v^6 + O(v^7) sage: f(z, z^2 + z) 1 + 2*z + 5*z^2 + 12*z^3 + 29*z^4 + 70*z^5 + 169*z^6 + O(z^7) sage: three = T(3)(a^2, b); three 3 sage: parent(three) Multivariate Polynomial Ring in a, b, c over Rational Field
>>> from sage.all import * >>> T = LazyPowerSeriesRing(QQ, names=('x', 'y',)); (x, y,) = T._first_ngens(2) >>> R = ZZ['a, b, c']; (a, b, c,) = R._first_ngens(3) >>> S = R['v']; (v,) = S._first_ngens(1) >>> L = LaurentPolynomialRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> parent(x(a, b)) Multivariate Polynomial Ring in a, b, c over Rational Field >>> parent(x(CC(Integer(2)), a)) Multivariate Polynomial Ring in a, b, c over Complex Field with 53 bits of precision >>> parent(x(Integer(0), Integer(0))) Rational Field >>> f = Integer(1) / (Integer(1) - x - y); f 1 + (x+y) + (x^2+2*x*y+y^2) + (x^3+3*x^2*y+3*x*y^2+y^3) + (x^4+4*x^3*y+6*x^2*y^2+4*x*y^3+y^4) + (x^5+5*x^4*y+10*x^3*y^2+10*x^2*y^3+5*x*y^4+y^5) + (x^6+6*x^5*y+15*x^4*y^2+20*x^3*y^3+15*x^2*y^4+6*x*y^5+y^6) + O(x,y)^7 >>> f(a**Integer(2), b*c) 1 + (a^2+b*c) + (a^4+2*a^2*b*c+b^2*c^2) + (a^6+3*a^4*b*c+3*a^2*b^2*c^2+b^3*c^3) + O(a,b,c)^7 >>> f(v, v**Integer(2)) 1 + v + 2*v^2 + 3*v^3 + 5*v^4 + 8*v^5 + 13*v^6 + O(v^7) >>> f(z, z**Integer(2) + z) 1 + 2*z + 5*z^2 + 12*z^3 + 29*z^4 + 70*z^5 + 169*z^6 + O(z^7) >>> three = T(Integer(3))(a**Integer(2), b); three 3 >>> parent(three) Multivariate Polynomial Ring in a, b, c over Rational Field
T.<x,y> = LazyPowerSeriesRing(QQ) R.<a,b,c> = ZZ[] S.<v> = R[] L.<z> = LaurentPolynomialRing(ZZ) parent(x(a, b)) parent(x(CC(2), a)) parent(x(0, 0)) f = 1 / (1 - x - y); f f(a^2, b*c) f(v, v^2) f(z, z^2 + z) three = T(3)(a^2, b); three parent(three)
- compositional_inverse()[source]¶
Return the compositional inverse of
self.Given a Taylor series \(f\) in one variable, the compositional inverse is a power series \(g\) over the same base ring, such that \((f \circ g)(z) = f(g(z)) = z\).
The compositional inverse exists if and only if:
\(\mathrm{val}(f) = 1\), or
\(f = a + b z\) with \(a, b \neq 0\).
EXAMPLES:
sage: L.<z> = LazyPowerSeriesRing(QQ) sage: (2*z).revert() 1/2*z sage: (z-z^2).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) sage: s = L(degree=1, constant=-1) sage: s.revert() -z - z^2 - z^3 + O(z^4) sage: s = L(degree=1, constant=1) sage: s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> (Integer(2)*z).revert() 1/2*z >>> (z-z**Integer(2)).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) >>> s = L(degree=Integer(1), constant=-Integer(1)) >>> s.revert() -z - z^2 - z^3 + O(z^4) >>> s = L(degree=Integer(1), constant=Integer(1)) >>> s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
L.<z> = LazyPowerSeriesRing(QQ) (2*z).revert() (z-z^2).revert() s = L(degree=1, constant=-1) s.revert() s = L(degree=1, constant=1) s.revert()
Warning
For series not known to be eventually constant (e.g., being defined by a function) with approximate valuation \(\leq 1\) (but not necessarily its true valuation), this assumes that this is the actual valuation:
sage: f = L(lambda n: n if n > 2 else 0) sage: f.revert() <repr(... failed: ValueError: generator already executing>
>>> from sage.all import * >>> f = L(lambda n: n if n > Integer(2) else Integer(0)) >>> f.revert() <repr(... failed: ValueError: generator already executing>
f = L(lambda n: n if n > 2 else 0) f.revert()
- compute_coefficients(i)[source]¶
Compute all the coefficients of
selfup toi.This method is deprecated, it has no effect anymore.
- derivative(*args)[source]¶
Return the derivative of the Taylor series.
Multiple variables and iteration counts may be supplied; see the documentation of
sage.calculus.functional.derivative()function for details.EXAMPLES:
sage: T.<z> = LazyPowerSeriesRing(ZZ) sage: z.derivative() 1 sage: (1 + z + z^2).derivative(3) 0 sage: (z^2 + z^4 + z^10).derivative(3) 24*z + 720*z^7 sage: (1 / (1-z)).derivative() 1 + 2*z + 3*z^2 + 4*z^3 + 5*z^4 + 6*z^5 + 7*z^6 + O(z^7) sage: T([1, 1, 1], constant=4).derivative() 1 + 2*z + 12*z^2 + 16*z^3 + 20*z^4 + 24*z^5 + 28*z^6 + O(z^7) sage: R.<q> = QQ[] sage: L.<x, y> = LazyPowerSeriesRing(R) sage: f = 1 / (1-q*x+y); f 1 + (q*x-y) + (q^2*x^2+(-2*q)*x*y+y^2) + (q^3*x^3+(-3*q^2)*x^2*y+3*q*x*y^2-y^3) + (q^4*x^4+(-4*q^3)*x^3*y+6*q^2*x^2*y^2+(-4*q)*x*y^3+y^4) + (q^5*x^5+(-5*q^4)*x^4*y+10*q^3*x^3*y^2+(-10*q^2)*x^2*y^3+5*q*x*y^4-y^5) + (q^6*x^6+(-6*q^5)*x^5*y+15*q^4*x^4*y^2+(-20*q^3)*x^3*y^3+15*q^2*x^2*y^4+(-6*q)*x*y^5+y^6) + O(x,y)^7 sage: f.derivative(q) x + (2*q*x^2+(-2)*x*y) + (3*q^2*x^3+(-6*q)*x^2*y+3*x*y^2) + (4*q^3*x^4+(-12*q^2)*x^3*y+12*q*x^2*y^2+(-4)*x*y^3) + (5*q^4*x^5+(-20*q^3)*x^4*y+30*q^2*x^3*y^2+(-20*q)*x^2*y^3+5*x*y^4) + (6*q^5*x^6+(-30*q^4)*x^5*y+60*q^3*x^4*y^2+(-60*q^2)*x^3*y^3+30*q*x^2*y^4+(-6)*x*y^5) + O(x,y)^7
>>> from sage.all import * >>> T = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = T._first_ngens(1) >>> z.derivative() 1 >>> (Integer(1) + z + z**Integer(2)).derivative(Integer(3)) 0 >>> (z**Integer(2) + z**Integer(4) + z**Integer(10)).derivative(Integer(3)) 24*z + 720*z^7 >>> (Integer(1) / (Integer(1)-z)).derivative() 1 + 2*z + 3*z^2 + 4*z^3 + 5*z^4 + 6*z^5 + 7*z^6 + O(z^7) >>> T([Integer(1), Integer(1), Integer(1)], constant=Integer(4)).derivative() 1 + 2*z + 12*z^2 + 16*z^3 + 20*z^4 + 24*z^5 + 28*z^6 + O(z^7) >>> R = QQ['q']; (q,) = R._first_ngens(1) >>> L = LazyPowerSeriesRing(R, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> f = Integer(1) / (Integer(1)-q*x+y); f 1 + (q*x-y) + (q^2*x^2+(-2*q)*x*y+y^2) + (q^3*x^3+(-3*q^2)*x^2*y+3*q*x*y^2-y^3) + (q^4*x^4+(-4*q^3)*x^3*y+6*q^2*x^2*y^2+(-4*q)*x*y^3+y^4) + (q^5*x^5+(-5*q^4)*x^4*y+10*q^3*x^3*y^2+(-10*q^2)*x^2*y^3+5*q*x*y^4-y^5) + (q^6*x^6+(-6*q^5)*x^5*y+15*q^4*x^4*y^2+(-20*q^3)*x^3*y^3+15*q^2*x^2*y^4+(-6*q)*x*y^5+y^6) + O(x,y)^7 >>> f.derivative(q) x + (2*q*x^2+(-2)*x*y) + (3*q^2*x^3+(-6*q)*x^2*y+3*x*y^2) + (4*q^3*x^4+(-12*q^2)*x^3*y+12*q*x^2*y^2+(-4)*x*y^3) + (5*q^4*x^5+(-20*q^3)*x^4*y+30*q^2*x^3*y^2+(-20*q)*x^2*y^3+5*x*y^4) + (6*q^5*x^6+(-30*q^4)*x^5*y+60*q^3*x^4*y^2+(-60*q^2)*x^3*y^3+30*q*x^2*y^4+(-6)*x*y^5) + O(x,y)^7
T.<z> = LazyPowerSeriesRing(ZZ) z.derivative() (1 + z + z^2).derivative(3) (z^2 + z^4 + z^10).derivative(3) (1 / (1-z)).derivative() T([1, 1, 1], constant=4).derivative() R.<q> = QQ[] L.<x, y> = LazyPowerSeriesRing(R) f = 1 / (1-q*x+y); f f.derivative(q)
Multivariate:
sage: L.<x,y,z> = LazyPowerSeriesRing(QQ) sage: f = (x + y^2 + z)^3; f (x^3+3*x^2*z+3*x*z^2+z^3) + (3*x^2*y^2+6*x*y^2*z+3*y^2*z^2) + (3*x*y^4+3*y^4*z) + y^6 sage: f.derivative(x) (3*x^2+6*x*z+3*z^2) + (6*x*y^2+6*y^2*z) + 3*y^4 sage: f.derivative(y, 5) 720*y sage: f.derivative(z, 5) 0 sage: f.derivative(x, y, z) 12*y sage: f = (1 + x + y^2 + z)^-1 sage: f.derivative(x) -1 + (2*x+2*z) + (-3*x^2+2*y^2-6*x*z-3*z^2) + ... + O(x,y,z)^6 sage: f.derivative(y, 2) -2 + (4*x+4*z) + (-6*x^2+12*y^2-12*x*z-6*z^2) + ... + O(x,y,z)^5 sage: f.derivative(x, y) 4*y + (-12*x*y-12*y*z) + (24*x^2*y-12*y^3+48*x*y*z+24*y*z^2) + (-40*x^3*y+48*x*y^3-120*x^2*y*z+48*y^3*z-120*x*y*z^2-40*y*z^3) + O(x,y,z)^5 sage: f.derivative(x, y, z) (-12*y) + (48*x*y+48*y*z) + (-120*x^2*y+48*y^3-240*x*y*z-120*y*z^2) + O(x,y,z)^4 sage: R.<t> = QQ[] sage: L.<x,y,z> = LazyPowerSeriesRing(R) sage: f = ((t^2-3)*x + t*y^2 - t*z)^2 sage: f.derivative(t,x,t,y) 24*t*y sage: f.derivative(t, 2) ((12*t^2-12)*x^2+(-12*t)*x*z+2*z^2) + (12*t*x*y^2+(-4)*y^2*z) + 2*y^4 sage: f.derivative(z, t) ((-6*t^2+6)*x+4*t*z) + ((-4*t)*y^2) sage: f.derivative(t, 10) 0 sage: f = (1 + t*(x + y + z))^-1 sage: f.derivative(x, t, y) 4*t + ((-18*t^2)*x+(-18*t^2)*y+(-18*t^2)*z) + (48*t^3*x^2+96*t^3*x*y+48*t^3*y^2+96*t^3*x*z+96*t^3*y*z+48*t^3*z^2) + ... + O(x,y,z)^5 sage: f.derivative(t, 2) (2*x^2+4*x*y+2*y^2+4*x*z+4*y*z+2*z^2) + ... + O(x,y,z)^7 sage: f.derivative(x, y, z, t) (-18*t^2) + (96*t^3*x+96*t^3*y+96*t^3*z) + ... + O(x,y,z)^4
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y', 'z',)); (x, y, z,) = L._first_ngens(3) >>> f = (x + y**Integer(2) + z)**Integer(3); f (x^3+3*x^2*z+3*x*z^2+z^3) + (3*x^2*y^2+6*x*y^2*z+3*y^2*z^2) + (3*x*y^4+3*y^4*z) + y^6 >>> f.derivative(x) (3*x^2+6*x*z+3*z^2) + (6*x*y^2+6*y^2*z) + 3*y^4 >>> f.derivative(y, Integer(5)) 720*y >>> f.derivative(z, Integer(5)) 0 >>> f.derivative(x, y, z) 12*y >>> f = (Integer(1) + x + y**Integer(2) + z)**-Integer(1) >>> f.derivative(x) -1 + (2*x+2*z) + (-3*x^2+2*y^2-6*x*z-3*z^2) + ... + O(x,y,z)^6 >>> f.derivative(y, Integer(2)) -2 + (4*x+4*z) + (-6*x^2+12*y^2-12*x*z-6*z^2) + ... + O(x,y,z)^5 >>> f.derivative(x, y) 4*y + (-12*x*y-12*y*z) + (24*x^2*y-12*y^3+48*x*y*z+24*y*z^2) + (-40*x^3*y+48*x*y^3-120*x^2*y*z+48*y^3*z-120*x*y*z^2-40*y*z^3) + O(x,y,z)^5 >>> f.derivative(x, y, z) (-12*y) + (48*x*y+48*y*z) + (-120*x^2*y+48*y^3-240*x*y*z-120*y*z^2) + O(x,y,z)^4 >>> R = QQ['t']; (t,) = R._first_ngens(1) >>> L = LazyPowerSeriesRing(R, names=('x', 'y', 'z',)); (x, y, z,) = L._first_ngens(3) >>> f = ((t**Integer(2)-Integer(3))*x + t*y**Integer(2) - t*z)**Integer(2) >>> f.derivative(t,x,t,y) 24*t*y >>> f.derivative(t, Integer(2)) ((12*t^2-12)*x^2+(-12*t)*x*z+2*z^2) + (12*t*x*y^2+(-4)*y^2*z) + 2*y^4 >>> f.derivative(z, t) ((-6*t^2+6)*x+4*t*z) + ((-4*t)*y^2) >>> f.derivative(t, Integer(10)) 0 >>> f = (Integer(1) + t*(x + y + z))**-Integer(1) >>> f.derivative(x, t, y) 4*t + ((-18*t^2)*x+(-18*t^2)*y+(-18*t^2)*z) + (48*t^3*x^2+96*t^3*x*y+48*t^3*y^2+96*t^3*x*z+96*t^3*y*z+48*t^3*z^2) + ... + O(x,y,z)^5 >>> f.derivative(t, Integer(2)) (2*x^2+4*x*y+2*y^2+4*x*z+4*y*z+2*z^2) + ... + O(x,y,z)^7 >>> f.derivative(x, y, z, t) (-18*t^2) + (96*t^3*x+96*t^3*y+96*t^3*z) + ... + O(x,y,z)^4
L.<x,y,z> = LazyPowerSeriesRing(QQ) f = (x + y^2 + z)^3; f f.derivative(x) f.derivative(y, 5) f.derivative(z, 5) f.derivative(x, y, z) f = (1 + x + y^2 + z)^-1 f.derivative(x) f.derivative(y, 2) f.derivative(x, y) f.derivative(x, y, z) R.<t> = QQ[] L.<x,y,z> = LazyPowerSeriesRing(R) f = ((t^2-3)*x + t*y^2 - t*z)^2 f.derivative(t,x,t,y) f.derivative(t, 2) f.derivative(z, t) f.derivative(t, 10) f = (1 + t*(x + y + z))^-1 f.derivative(x, t, y) f.derivative(t, 2) f.derivative(x, y, z, t)
- exponential()[source]¶
Return the exponential series of
self.This method is deprecated, use
exp()instead.
- integral(variable, constants=None)[source]¶
Return the integral of
selfwith respect tovariable.INPUT:
variable– (optional) the variable to integrateconstants– (optional; keyword-only) list of integration constants for the integrals ofself(the last constant corresponds to the first integral)
For multivariable series, only
variableshould be specified; the integration constant is taken to be \(0\).Now we assume the series is univariate. If the first argument is a list, then this method iterprets it as integration constants. If it is a positive integer, the method interprets it as the number of times to integrate the function. If
variableis not the variable of the power series, then the coefficients are integrated with respect tovariable. If the integration constants are not specified, they are considered to be \(0\).EXAMPLES:
sage: L.<t> = LazyPowerSeriesRing(QQ) sage: f = 2 + 3*t + t^5 sage: f.integral() 2*t + 3/2*t^2 + 1/6*t^6 sage: f.integral([-2, -2]) -2 - 2*t + t^2 + 1/2*t^3 + 1/42*t^7 sage: f.integral(t) 2*t + 3/2*t^2 + 1/6*t^6 sage: f.integral(2) t^2 + 1/2*t^3 + 1/42*t^7 sage: (t^3 + t^5).integral() 1/4*t^4 + 1/6*t^6 sage: L.zero().integral() 0 sage: L.zero().integral([0, 1, 2, 3]) t + t^2 + 1/2*t^3 sage: L([1, 2 ,3], constant=4).integral() t + t^2 + t^3 + t^4 + 4/5*t^5 + 2/3*t^6 + O(t^7)
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('t',)); (t,) = L._first_ngens(1) >>> f = Integer(2) + Integer(3)*t + t**Integer(5) >>> f.integral() 2*t + 3/2*t^2 + 1/6*t^6 >>> f.integral([-Integer(2), -Integer(2)]) -2 - 2*t + t^2 + 1/2*t^3 + 1/42*t^7 >>> f.integral(t) 2*t + 3/2*t^2 + 1/6*t^6 >>> f.integral(Integer(2)) t^2 + 1/2*t^3 + 1/42*t^7 >>> (t**Integer(3) + t**Integer(5)).integral() 1/4*t^4 + 1/6*t^6 >>> L.zero().integral() 0 >>> L.zero().integral([Integer(0), Integer(1), Integer(2), Integer(3)]) t + t^2 + 1/2*t^3 >>> L([Integer(1), Integer(2) ,Integer(3)], constant=Integer(4)).integral() t + t^2 + t^3 + t^4 + 4/5*t^5 + 2/3*t^6 + O(t^7)
L.<t> = LazyPowerSeriesRing(QQ) f = 2 + 3*t + t^5 f.integral() f.integral([-2, -2]) f.integral(t) f.integral(2) (t^3 + t^5).integral() L.zero().integral() L.zero().integral([0, 1, 2, 3]) L([1, 2 ,3], constant=4).integral()
We solve the ODE \(f'' - f' - 2 f = 0\) by solving for \(f''\), then integrating and applying a recursive definition:
sage: R.<C, D> = QQ[] sage: L.<x> = LazyPowerSeriesRing(R) sage: f = L.undefined() sage: f.define((f.derivative() + 2*f).integral(constants=[C, D])) sage: f C + D*x + ((C+1/2*D)*x^2) + ((1/3*C+1/2*D)*x^3) + ((1/4*C+5/24*D)*x^4) + ((1/12*C+11/120*D)*x^5) + ((11/360*C+7/240*D)*x^6) + O(x^7) sage: f.derivative(2) - f.derivative() - 2*f O(x^7)
>>> from sage.all import * >>> R = QQ['C, D']; (C, D,) = R._first_ngens(2) >>> L = LazyPowerSeriesRing(R, names=('x',)); (x,) = L._first_ngens(1) >>> f = L.undefined() >>> f.define((f.derivative() + Integer(2)*f).integral(constants=[C, D])) >>> f C + D*x + ((C+1/2*D)*x^2) + ((1/3*C+1/2*D)*x^3) + ((1/4*C+5/24*D)*x^4) + ((1/12*C+11/120*D)*x^5) + ((11/360*C+7/240*D)*x^6) + O(x^7) >>> f.derivative(Integer(2)) - f.derivative() - Integer(2)*f O(x^7)
R.<C, D> = QQ[] L.<x> = LazyPowerSeriesRing(R) f = L.undefined() f.define((f.derivative() + 2*f).integral(constants=[C, D])) f f.derivative(2) - f.derivative() - 2*f
We compare this with the answer we get from the characteristic polynomial:
sage: g = C * exp(-x) + D * exp(2*x); g (C+D) + ((-C+2*D)*x) + ((1/2*C+2*D)*x^2) + ((-1/6*C+4/3*D)*x^3) + ((1/24*C+2/3*D)*x^4) + ((-1/120*C+4/15*D)*x^5) + ((1/720*C+4/45*D)*x^6) + O(x^7) sage: g.derivative(2) - g.derivative() - 2*g O(x^7)
>>> from sage.all import * >>> g = C * exp(-x) + D * exp(Integer(2)*x); g (C+D) + ((-C+2*D)*x) + ((1/2*C+2*D)*x^2) + ((-1/6*C+4/3*D)*x^3) + ((1/24*C+2/3*D)*x^4) + ((-1/120*C+4/15*D)*x^5) + ((1/720*C+4/45*D)*x^6) + O(x^7) >>> g.derivative(Integer(2)) - g.derivative() - Integer(2)*g O(x^7)
g = C * exp(-x) + D * exp(2*x); g g.derivative(2) - g.derivative() - 2*g
Note that
CandDare playing different roles, so we need to perform a substitution to the coefficients offto recover the solutiong:sage: fp = f.map_coefficients(lambda c: c(C=C+D, D=2*D-C)); fp (C+D) + ((-C+2*D)*x) + ((1/2*C+2*D)*x^2) + ((-1/6*C+4/3*D)*x^3) + ((1/24*C+2/3*D)*x^4) + ((-1/120*C+4/15*D)*x^5) + ((1/720*C+4/45*D)*x^6) + O(x^7) sage: fp - g O(x^7)
>>> from sage.all import * >>> fp = f.map_coefficients(lambda c: c(C=C+D, D=Integer(2)*D-C)); fp (C+D) + ((-C+2*D)*x) + ((1/2*C+2*D)*x^2) + ((-1/6*C+4/3*D)*x^3) + ((1/24*C+2/3*D)*x^4) + ((-1/120*C+4/15*D)*x^5) + ((1/720*C+4/45*D)*x^6) + O(x^7) >>> fp - g O(x^7)
fp = f.map_coefficients(lambda c: c(C=C+D, D=2*D-C)); fp fp - g
We can integrate both the series and coefficients:
sage: R.<x,y,z> = QQ[] sage: L.<t> = LazyPowerSeriesRing(R) sage: f = (x*t^2 + y*t + z)^2; f z^2 + 2*y*z*t + ((y^2+2*x*z)*t^2) + 2*x*y*t^3 + x^2*t^4 sage: f.integral(x) x*z^2 + 2*x*y*z*t + ((x*y^2+x^2*z)*t^2) + x^2*y*t^3 + 1/3*x^3*t^4 sage: f.integral(t) z^2*t + y*z*t^2 + ((1/3*y^2+2/3*x*z)*t^3) + 1/2*x*y*t^4 + 1/5*x^2*t^5 sage: f.integral(y, constants=[x*y*z]) x*y*z + y*z^2*t + 1/2*y^2*z*t^2 + ((1/9*y^3+2/3*x*y*z)*t^3) + 1/4*x*y^2*t^4 + 1/5*x^2*y*t^5
>>> from sage.all import * >>> R = QQ['x, y, z']; (x, y, z,) = R._first_ngens(3) >>> L = LazyPowerSeriesRing(R, names=('t',)); (t,) = L._first_ngens(1) >>> f = (x*t**Integer(2) + y*t + z)**Integer(2); f z^2 + 2*y*z*t + ((y^2+2*x*z)*t^2) + 2*x*y*t^3 + x^2*t^4 >>> f.integral(x) x*z^2 + 2*x*y*z*t + ((x*y^2+x^2*z)*t^2) + x^2*y*t^3 + 1/3*x^3*t^4 >>> f.integral(t) z^2*t + y*z*t^2 + ((1/3*y^2+2/3*x*z)*t^3) + 1/2*x*y*t^4 + 1/5*x^2*t^5 >>> f.integral(y, constants=[x*y*z]) x*y*z + y*z^2*t + 1/2*y^2*z*t^2 + ((1/9*y^3+2/3*x*y*z)*t^3) + 1/4*x*y^2*t^4 + 1/5*x^2*y*t^5
R.<x,y,z> = QQ[] L.<t> = LazyPowerSeriesRing(R) f = (x*t^2 + y*t + z)^2; f f.integral(x) f.integral(t) f.integral(y, constants=[x*y*z])
We can integrate multivariate power series:
sage: R.<t> = QQ[] sage: L.<x,y,z> = LazyPowerSeriesRing(R) sage: f = ((t^2 + t) - t * y^2 + t^2 * (y + z))^2; f (t^4+2*t^3+t^2) + ((2*t^4+2*t^3)*y+(2*t^4+2*t^3)*z) + ((t^4-2*t^3-2*t^2)*y^2+2*t^4*y*z+t^4*z^2) + ((-2*t^3)*y^3+(-2*t^3)*y^2*z) + t^2*y^4 sage: g = f.integral(x); g ((t^4+2*t^3+t^2)*x) + ((2*t^4+2*t^3)*x*y+(2*t^4+2*t^3)*x*z) + ((t^4-2*t^3-2*t^2)*x*y^2+2*t^4*x*y*z+t^4*x*z^2) + ((-2*t^3)*x*y^3+(-2*t^3)*x*y^2*z) + t^2*x*y^4 sage: g[0] 0 sage: g[1] (t^4 + 2*t^3 + t^2)*x sage: g[2] (2*t^4 + 2*t^3)*x*y + (2*t^4 + 2*t^3)*x*z sage: f.integral(z) ((t^4+2*t^3+t^2)*z) + ((2*t^4+2*t^3)*y*z+(t^4+t^3)*z^2) + ((t^4-2*t^3-2*t^2)*y^2*z+t^4*y*z^2+1/3*t^4*z^3) + ((-2*t^3)*y^3*z+(-t^3)*y^2*z^2) + t^2*y^4*z sage: f.integral(t) (1/5*t^5+1/2*t^4+1/3*t^3) + ((2/5*t^5+1/2*t^4)*y+(2/5*t^5+1/2*t^4)*z) + ((1/5*t^5-1/2*t^4-2/3*t^3)*y^2+2/5*t^5*y*z+1/5*t^5*z^2) + ((-1/2*t^4)*y^3+(-1/2*t^4)*y^2*z) + 1/3*t^3*y^4 sage: L.<x,y,z> = LazyPowerSeriesRing(QQ) sage: (x + y - z^2).integral(z) (x*z+y*z) + (-1/3*z^3)
>>> from sage.all import * >>> R = QQ['t']; (t,) = R._first_ngens(1) >>> L = LazyPowerSeriesRing(R, names=('x', 'y', 'z',)); (x, y, z,) = L._first_ngens(3) >>> f = ((t**Integer(2) + t) - t * y**Integer(2) + t**Integer(2) * (y + z))**Integer(2); f (t^4+2*t^3+t^2) + ((2*t^4+2*t^3)*y+(2*t^4+2*t^3)*z) + ((t^4-2*t^3-2*t^2)*y^2+2*t^4*y*z+t^4*z^2) + ((-2*t^3)*y^3+(-2*t^3)*y^2*z) + t^2*y^4 >>> g = f.integral(x); g ((t^4+2*t^3+t^2)*x) + ((2*t^4+2*t^3)*x*y+(2*t^4+2*t^3)*x*z) + ((t^4-2*t^3-2*t^2)*x*y^2+2*t^4*x*y*z+t^4*x*z^2) + ((-2*t^3)*x*y^3+(-2*t^3)*x*y^2*z) + t^2*x*y^4 >>> g[Integer(0)] 0 >>> g[Integer(1)] (t^4 + 2*t^3 + t^2)*x >>> g[Integer(2)] (2*t^4 + 2*t^3)*x*y + (2*t^4 + 2*t^3)*x*z >>> f.integral(z) ((t^4+2*t^3+t^2)*z) + ((2*t^4+2*t^3)*y*z+(t^4+t^3)*z^2) + ((t^4-2*t^3-2*t^2)*y^2*z+t^4*y*z^2+1/3*t^4*z^3) + ((-2*t^3)*y^3*z+(-t^3)*y^2*z^2) + t^2*y^4*z >>> f.integral(t) (1/5*t^5+1/2*t^4+1/3*t^3) + ((2/5*t^5+1/2*t^4)*y+(2/5*t^5+1/2*t^4)*z) + ((1/5*t^5-1/2*t^4-2/3*t^3)*y^2+2/5*t^5*y*z+1/5*t^5*z^2) + ((-1/2*t^4)*y^3+(-1/2*t^4)*y^2*z) + 1/3*t^3*y^4 >>> L = LazyPowerSeriesRing(QQ, names=('x', 'y', 'z',)); (x, y, z,) = L._first_ngens(3) >>> (x + y - z**Integer(2)).integral(z) (x*z+y*z) + (-1/3*z^3)
R.<t> = QQ[] L.<x,y,z> = LazyPowerSeriesRing(R) f = ((t^2 + t) - t * y^2 + t^2 * (y + z))^2; f g = f.integral(x); g g[0] g[1] g[2] f.integral(z) f.integral(t) L.<x,y,z> = LazyPowerSeriesRing(QQ) (x + y - z^2).integral(z)
- is_unit()[source]¶
Return whether this element is a unit in the ring.
EXAMPLES:
sage: L.<z> = LazyPowerSeriesRing(ZZ) sage: (2*z).is_unit() False sage: (1 + 2*z).is_unit() True sage: (3 + 2*z).is_unit() False sage: L.<x,y> = LazyPowerSeriesRing(ZZ) sage: (-1 + 2*x + 3*x*y).is_unit() True
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('z',)); (z,) = L._first_ngens(1) >>> (Integer(2)*z).is_unit() False >>> (Integer(1) + Integer(2)*z).is_unit() True >>> (Integer(3) + Integer(2)*z).is_unit() False >>> L = LazyPowerSeriesRing(ZZ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> (-Integer(1) + Integer(2)*x + Integer(3)*x*y).is_unit() True
L.<z> = LazyPowerSeriesRing(ZZ) (2*z).is_unit() (1 + 2*z).is_unit() (3 + 2*z).is_unit() L.<x,y> = LazyPowerSeriesRing(ZZ) (-1 + 2*x + 3*x*y).is_unit()
- polynomial(degree=None, names=None)[source]¶
Return
selfas a polynomial ifselfis actually so.INPUT:
degree–Noneor an integernames– names of the variables; if it isNone, the name of the variables of the series is used
OUTPUT:
If
degreeis notNone, the terms of the series of degree greater thandegreeare first truncated. IfdegreeisNoneand the series is not a polynomial polynomial, aValueErroris raised.EXAMPLES:
sage: L.<x,y> = LazyPowerSeriesRing(ZZ) sage: f = x^2 + y*x - x + 2; f 2 + (-x) + (x^2+x*y) sage: f.polynomial() x^2 + x*y - x + 2
>>> from sage.all import * >>> L = LazyPowerSeriesRing(ZZ, names=('x', 'y',)); (x, y,) = L._first_ngens(2) >>> f = x**Integer(2) + y*x - x + Integer(2); f 2 + (-x) + (x^2+x*y) >>> f.polynomial() x^2 + x*y - x + 2
L.<x,y> = LazyPowerSeriesRing(ZZ) f = x^2 + y*x - x + 2; f f.polynomial()
- revert()[source]¶
Return the compositional inverse of
self.Given a Taylor series \(f\) in one variable, the compositional inverse is a power series \(g\) over the same base ring, such that \((f \circ g)(z) = f(g(z)) = z\).
The compositional inverse exists if and only if:
\(\mathrm{val}(f) = 1\), or
\(f = a + b z\) with \(a, b \neq 0\).
EXAMPLES:
sage: L.<z> = LazyPowerSeriesRing(QQ) sage: (2*z).revert() 1/2*z sage: (z-z^2).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) sage: s = L(degree=1, constant=-1) sage: s.revert() -z - z^2 - z^3 + O(z^4) sage: s = L(degree=1, constant=1) sage: s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('z',)); (z,) = L._first_ngens(1) >>> (Integer(2)*z).revert() 1/2*z >>> (z-z**Integer(2)).revert() z + z^2 + 2*z^3 + 5*z^4 + 14*z^5 + 42*z^6 + 132*z^7 + O(z^8) >>> s = L(degree=Integer(1), constant=-Integer(1)) >>> s.revert() -z - z^2 - z^3 + O(z^4) >>> s = L(degree=Integer(1), constant=Integer(1)) >>> s.revert() z - z^2 + z^3 - z^4 + z^5 - z^6 + z^7 + O(z^8)
L.<z> = LazyPowerSeriesRing(QQ) (2*z).revert() (z-z^2).revert() s = L(degree=1, constant=-1) s.revert() s = L(degree=1, constant=1) s.revert()
Warning
For series not known to be eventually constant (e.g., being defined by a function) with approximate valuation \(\leq 1\) (but not necessarily its true valuation), this assumes that this is the actual valuation:
sage: f = L(lambda n: n if n > 2 else 0) sage: f.revert() <repr(... failed: ValueError: generator already executing>
>>> from sage.all import * >>> f = L(lambda n: n if n > Integer(2) else Integer(0)) >>> f.revert() <repr(... failed: ValueError: generator already executing>
f = L(lambda n: n if n > 2 else 0) f.revert()
- class sage.rings.lazy_series.LazyPowerSeries_gcd_mixin[source]¶
Bases:
objectA lazy power series that also implements the GCD algorithm.
- gcd(other)[source]¶
Return the greatest common divisor of
selfandother.EXAMPLES:
sage: L.<x> = LazyPowerSeriesRing(QQ) sage: a = 16*x^5 / (1 - 5*x) sage: b = (22*x^2 + x^8) / (1 - 4*x^2) sage: a.gcd(b) x^2
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x',)); (x,) = L._first_ngens(1) >>> a = Integer(16)*x**Integer(5) / (Integer(1) - Integer(5)*x) >>> b = (Integer(22)*x**Integer(2) + x**Integer(8)) / (Integer(1) - Integer(4)*x**Integer(2)) >>> a.gcd(b) x^2
L.<x> = LazyPowerSeriesRing(QQ) a = 16*x^5 / (1 - 5*x) b = (22*x^2 + x^8) / (1 - 4*x^2) a.gcd(b)
- xgcd(f)[source]¶
Return the extended gcd of
selfandf.OUTPUT:
A triple
(g, s, t)such thatgis the gcd ofselfandf, andsandtare cofactors satisfying the Bezout identity\[g = s \cdot \mathrm{self} + t \cdot f.\]EXAMPLES:
sage: L.<x> = LazyPowerSeriesRing(QQ) sage: a = 16*x^5 / (1 - 2*x) sage: b = (22*x^3 + x^8) / (1 - 3*x^2) sage: g, s, t = a.xgcd(b) sage: g x^3 sage: s 1/22 - 41/242*x^2 - 8/121*x^3 + 120/1331*x^4 + 1205/5324*x^5 + 316/14641*x^6 + O(x^7) sage: t 1/22 - 41/242*x^2 - 8/121*x^3 + 120/1331*x^4 + 1205/5324*x^5 + 316/14641*x^6 + O(x^7) sage: LazyPowerSeriesRing.options.halting_precision(20) # verify up to degree 20 sage: g == s * a + t * b True sage: a = 16*x^5 / (1 - 2*x) sage: b = (-16*x^5 + x^8) / (1 - 3*x^2) sage: g, s, t = a.xgcd(b) sage: g x^5 sage: s 1/16 - 1/16*x - 3/16*x^2 + 1/8*x^3 - 17/256*x^4 + 9/128*x^5 + 1/128*x^6 + O(x^7) sage: t 1/16*x - 1/16*x^2 - 3/16*x^3 + 1/8*x^4 - 17/256*x^5 + 9/128*x^6 + 1/128*x^7 + O(x^8) sage: g == s * a + t * b True sage: # needs sage.rings.finite_rings sage: L.<x> = LazyPowerSeriesRing(GF(2)) sage: a = L(lambda n: n % 2, valuation=3); a x^3 + x^5 + x^7 + x^9 + O(x^10) sage: b = L(lambda n: binomial(n,2) % 2, valuation=3); b x^3 + x^6 + x^7 + O(x^10) sage: g, s, t = a.xgcd(b) sage: g x^3 sage: s 1 + x + x^3 + x^4 + x^5 + O(x^7) sage: t x + x^2 + x^4 + x^5 + x^6 + O(x^8) sage: g == s * a + t * b True sage: LazyPowerSeriesRing.options._reset() # reset the options
>>> from sage.all import * >>> L = LazyPowerSeriesRing(QQ, names=('x',)); (x,) = L._first_ngens(1) >>> a = Integer(16)*x**Integer(5) / (Integer(1) - Integer(2)*x) >>> b = (Integer(22)*x**Integer(3) + x**Integer(8)) / (Integer(1) - Integer(3)*x**Integer(2)) >>> g, s, t = a.xgcd(b) >>> g x^3 >>> s 1/22 - 41/242*x^2 - 8/121*x^3 + 120/1331*x^4 + 1205/5324*x^5 + 316/14641*x^6 + O(x^7) >>> t 1/22 - 41/242*x^2 - 8/121*x^3 + 120/1331*x^4 + 1205/5324*x^5 + 316/14641*x^6 + O(x^7) >>> LazyPowerSeriesRing.options.halting_precision(Integer(20)) # verify up to degree 20 >>> g == s * a + t * b True >>> a = Integer(16)*x**Integer(5) / (Integer(1) - Integer(2)*x) >>> b = (-Integer(16)*x**Integer(5) + x**Integer(8)) / (Integer(1) - Integer(3)*x**Integer(2)) >>> g, s, t = a.xgcd(b) >>> g x^5 >>> s 1/16 - 1/16*x - 3/16*x^2 + 1/8*x^3 - 17/256*x^4 + 9/128*x^5 + 1/128*x^6 + O(x^7) >>> t 1/16*x - 1/16*x^2 - 3/16*x^3 + 1/8*x^4 - 17/256*x^5 + 9/128*x^6 + 1/128*x^7 + O(x^8) >>> g == s * a + t * b True >>> # needs sage.rings.finite_rings >>> L = LazyPowerSeriesRing(GF(Integer(2)), names=('x',)); (x,) = L._first_ngens(1) >>> a = L(lambda n: n % Integer(2), valuation=Integer(3)); a x^3 + x^5 + x^7 + x^9 + O(x^10) >>> b = L(lambda n: binomial(n,Integer(2)) % Integer(2), valuation=Integer(3)); b x^3 + x^6 + x^7 + O(x^10) >>> g, s, t = a.xgcd(b) >>> g x^3 >>> s 1 + x + x^3 + x^4 + x^5 + O(x^7) >>> t x + x^2 + x^4 + x^5 + x^6 + O(x^8) >>> g == s * a + t * b True >>> LazyPowerSeriesRing.options._reset() # reset the options
L.<x> = LazyPowerSeriesRing(QQ) a = 16*x^5 / (1 - 2*x) b = (22*x^3 + x^8) / (1 - 3*x^2) g, s, t = a.xgcd(b) g s t LazyPowerSeriesRing.options.halting_precision(20) # verify up to degree 20 g == s * a + t * b a = 16*x^5 / (1 - 2*x) b = (-16*x^5 + x^8) / (1 - 3*x^2) g, s, t = a.xgcd(b) g s t g == s * a + t * b # needs sage.rings.finite_rings L.<x> = LazyPowerSeriesRing(GF(2)) a = L(lambda n: n % 2, valuation=3); a b = L(lambda n: binomial(n,2) % 2, valuation=3); b g, s, t = a.xgcd(b) g s t g == s * a + t * b LazyPowerSeriesRing.options._reset() # reset the options
- class sage.rings.lazy_series.LazySymmetricFunction(parent, coeff_stream)[source]¶
Bases:
LazyCompletionGradedAlgebraElementA symmetric function where each degree is computed lazily.
EXAMPLES:
sage: s = SymmetricFunctions(ZZ).s() # needs sage.modules sage: L = LazySymmetricFunctions(s) # needs sage.modules
>>> from sage.all import * >>> s = SymmetricFunctions(ZZ).s() # needs sage.modules >>> L = LazySymmetricFunctions(s) # needs sage.modules
s = SymmetricFunctions(ZZ).s() # needs sage.modules L = LazySymmetricFunctions(s) # needs sage.modules
- arithmetic_product(*args)[source]¶
Return the arithmetic product of
selfwithg.The arithmetic product is a binary operation \(\boxdot\) on the ring of symmetric functions which is bilinear in its two arguments and satisfies
\[p_{\lambda} \boxdot p_{\mu} = \prod\limits_{i \geq 1, j \geq 1} p_{\mathrm{lcm}(\lambda_i, \mu_j)}^{\mathrm{gcd}(\lambda_i, \mu_j)}\]for any two partitions \(\lambda = (\lambda_1, \lambda_2, \lambda_3, \dots )\) and \(\mu = (\mu_1, \mu_2, \mu_3, \dots )\) (where \(p_{\nu}\) denotes the power-sum symmetric function indexed by the partition \(\nu\), and \(p_i\) denotes the \(i\)-th power-sum symmetric function). This is enough to define the arithmetic product if the base ring is torsion-free as a \(\ZZ\)-module; for all other cases the arithmetic product is uniquely determined by requiring it to be functorial in the base ring. See http://mathoverflow.net/questions/138148/ for a discussion of this arithmetic product.
Warning
The operation \(f \boxdot g\) was originally defined only for symmetric functions \(f\) and \(g\) without constant term. We extend this definition using the convention that the least common multiple of any integer with \(0\) is \(0\).
If \(f\) and \(g\) are two symmetric functions which are homogeneous of degrees \(a\) and \(b\), respectively, then \(f \boxdot g\) is homogeneous of degree \(ab\).
The arithmetic product is commutative and associative and has unity \(e_1 = p_1 = h_1\).
For species \(M\) and \(N\) such that \(M[\varnothing] = N[\varnothing] = \varnothing\), their arithmetic product is the species \(M \boxdot N\) of “\(M\)-assemblies of cloned \(N\)-structures”. This operation is defined and several examples are given in [MM2008].
INPUT:
g– a cycle index series having the same parent asself
OUTPUT: the arithmetic product of
selfwithgEXAMPLES:
For \(C\) the species of (oriented) cycles and \(L_{+}\) the species of nonempty linear orders, \(C \boxdot L_{+}\) corresponds to the species of “regular octopuses”; a \((C \boxdot L_{+})\)-structure is a cycle of some length, each of whose elements is an ordered list of a length which is consistent for all the lists in the structure.
sage: R.<q> = QQ[] sage: p = SymmetricFunctions(R).p() # needs sage.modules sage: m = SymmetricFunctions(R).m() # needs sage.modules sage: L = LazySymmetricFunctions(m) # needs sage.modules sage: # needs sage.modules sage: C = species.CycleSpecies().cycle_index_series() sage: c = L(lambda n: C[n]) sage: Lplus = L(lambda n: p([1]*n), valuation=1) sage: r = c.arithmetic_product(Lplus); r # needs sage.libs.pari m[1] + (3*m[1,1]+2*m[2]) + (8*m[1,1,1]+4*m[2,1]+2*m[3]) + (42*m[1,1,1,1]+21*m[2,1,1]+12*m[2,2]+7*m[3,1]+3*m[4]) + (144*m[1,1,1,1,1]+72*m[2,1,1,1]+36*m[2,2,1]+24*m[3,1,1]+12*m[3,2]+6*m[4,1]+2*m[5]) + ... + O^7
>>> from sage.all import * >>> R = QQ['q']; (q,) = R._first_ngens(1) >>> p = SymmetricFunctions(R).p() # needs sage.modules >>> m = SymmetricFunctions(R).m() # needs sage.modules >>> L = LazySymmetricFunctions(m) # needs sage.modules >>> # needs sage.modules >>> C = species.CycleSpecies().cycle_index_series() >>> c = L(lambda n: C[n]) >>> Lplus = L(lambda n: p([Integer(1)]*n), valuation=Integer(1)) >>> r = c.arithmetic_product(Lplus); r # needs sage.libs.pari m[1] + (3*m[1,1]+2*m[2]) + (8*m[1,1,1]+4*m[2,1]+2*m[3]) + (42*m[1,1,1,1]+21*m[2,1,1]+12*m[2,2]+7*m[3,1]+3*m[4]) + (144*m[1,1,1,1,1]+72*m[2,1,1,1]+36*m[2,2,1]+24*m[3,1,1]+12*m[3,2]+6*m[4,1]+2*m[5]) + ... + O^7
R.<q> = QQ[] p = SymmetricFunctions(R).p() # needs sage.modules m = SymmetricFunctions(R).m() # needs sage.modules L = LazySymmetricFunctions(m) # needs sage.modules # needs sage.modules C = species.CycleSpecies().cycle_index_series() c = L(lambda n: C[n]) Lplus = L(lambda n: p([1]*n), valuation=1) r = c.arithmetic_product(Lplus); r # needs sage.libs.pari
In particular, the number of regular octopuses is:
sage: [r[n].coefficient([1]*n) for n in range(8)] # needs sage.libs.pari sage.modules [0, 1, 3, 8, 42, 144, 1440, 5760]
>>> from sage.all import * >>> [r[n].coefficient([Integer(1)]*n) for n in range(Integer(8))] # needs sage.libs.pari sage.modules [0, 1, 3, 8, 42, 144, 1440, 5760]
[r[n].coefficient([1]*n) for n in range(8)] # needs sage.libs.pari sage.modules
It is shown in [MM2008] that the exponential generating function for regular octopuses satisfies \((C \boxdot L_{+}) (x) = \sum_{n \geq 1} \sigma (n) (n - 1)! \frac{x^{n}}{n!}\) (where \(\sigma (n)\) is the sum of the divisors of \(n\)).
sage: [sum(divisors(i))*factorial(i-1) for i in range(1,8)] # needs sage.modules [1, 3, 8, 42, 144, 1440, 5760]
>>> from sage.all import * >>> [sum(divisors(i))*factorial(i-Integer(1)) for i in range(Integer(1),Integer(8))] # needs sage.modules [1, 3, 8, 42, 144, 1440, 5760]
[sum(divisors(i))*factorial(i-1) for i in range(1,8)] # needs sage.modules
AUTHORS:
Andrew Gainer-Dewar (2013)
REFERENCES:
- compositional_inverse()[source]¶
Return the compositional inverse of
self.Given a symmetric function \(f\), the compositional inverse is a symmetric function \(g\) over the same base ring, such that \(f \circ g = p_1\). Thus, it is the inverse with respect to plethystic substitution.
The compositional inverse exists if and only if:
\(\mathrm{val}(f) = 1\), or
\(f = a + b p_1\) with \(a, b \neq 0\).
See also
EXAMPLES:
sage: # needs sage.modules sage: h = SymmetricFunctions(QQ).h() sage: L = LazySymmetricFunctions(h) sage: f = L(lambda n: h[n]) - 1 sage: f(f.revert()) h[1] + O^8
>>> from sage.all import * >>> # needs sage.modules >>> h = SymmetricFunctions(QQ).h() >>> L = LazySymmetricFunctions(h) >>> f = L(lambda n: h[n]) - Integer(1) >>> f(f.revert()) h[1] + O^8
# needs sage.modules h = SymmetricFunctions(QQ).h() L = LazySymmetricFunctions(h) f = L(lambda n: h[n]) - 1 f(f.revert())
ALGORITHM:
Let \(F\) be a symmetric function with valuation \(1\), i.e., whose constant term vanishes and whose degree one term equals \(b p_1\). Then
\[(F - b p_1) \circ G = F \circ G - b p_1 \circ G = p_1 - b G,\]and therefore \(G = (p_1 - (F - b p_1) \circ G) / b\), which allows recursive computation of \(G\).
See also
The compositional inverse \(\Omega\) of the symmetric function \(h_1 + h_2 + \dots\) can be handled much more efficiently using specialized methods. See
LogarithmCycleIndexSeries()AUTHORS:
Andrew Gainer-Dewar
Martin Rubey
- derivative_with_respect_to_p1(n=1)[source]¶
Return the symmetric function obtained by taking the derivative of
selfwith respect to the power-sum symmetric function \(p_1\) when the expansion ofselfin the power-sum basis is considered as a polynomial in \(p_k\)’s (with \(k \geq 1\)).This is the same as skewing
selfby the first power-sum symmetric function \(p_1\).INPUT:
n– (default: 1) nonnegative integer which determines which power of the derivative is taken
EXAMPLES:
The species \(E\) of sets satisfies the relationship \(E' = E\):
sage: # needs sage.modules sage: h = SymmetricFunctions(QQ).h() sage: T = LazySymmetricFunctions(h) sage: E = T(lambda n: h[n]) sage: E - E.derivative_with_respect_to_p1() O^6
>>> from sage.all import * >>> # needs sage.modules >>> h = SymmetricFunctions(QQ).h() >>> T = LazySymmetricFunctions(h) >>> E = T(lambda n: h[n]) >>> E - E.derivative_with_respect_to_p1() O^6
# needs sage.modules h = SymmetricFunctions(QQ).h() T = LazySymmetricFunctions(h) E = T(lambda n: h[n]) E - E.derivative_with_respect_to_p1()
The species \(C\) of cyclic orderings and the species \(L\) of linear orderings satisfy the relationship \(C' = L\):
sage: # needs sage.modules sage: p = SymmetricFunctions(QQ).p() sage: C = T(lambda n: (sum(euler_phi(k)*p([k])**(n//k) ....: for k in divisors(n))/n if n > 0 else 0)) sage: L = T(lambda n: p([1]*n)) sage: L - C.derivative_with_respect_to_p1() # needs sage.libs.pari O^6
>>> from sage.all import * >>> # needs sage.modules >>> p = SymmetricFunctions(QQ).p() >>> C = T(lambda n: (sum(euler_phi(k)*p([k])**(n//k) ... for k in divisors(n))/n if n > Integer(0) else Integer(0))) >>> L = T(lambda n: p([Integer(1)]*n)) >>> L - C.derivative_with_respect_to_p1() # needs sage.libs.pari O^6
# needs sage.modules p = SymmetricFunctions(QQ).p() C = T(lambda n: (sum(euler_phi(k)*p([k])**(n//k) for k in divisors(n))/n if n > 0 else 0)) L = T(lambda n: p([1]*n)) L - C.derivative_with_respect_to_p1() # needs sage.libs.pari
- functorial_composition(*args)[source]¶
Return the functorial composition of
selfandg.Let \(X\) be a finite set of cardinality \(m\). For a group action of the symmetric group \(g: S_n \to S_X\) and a (possibly virtual) representation of the symmetric group on \(X\), \(f: S_X \to GL(V)\), the functorial composition is the (virtual) representation of the symmetric group \(f \Box g: S_n \to GL(V)\) given by \(\sigma \mapsto f(g(\sigma))\).
This is more naturally phrased in the language of combinatorial species. Let \(F\) and \(G\) be species, then their functorial composition is the species \(F \Box G\) with \((F \Box G) [A] = F[ G[A] ]\). In other words, an \((F \Box G)\)-structure on a set \(A\) of labels is an \(F\)-structure whose labels are the set of all \(G\)-structures on \(A\).
The Frobenius character (or cycle index series) of \(F \Box G\) can be computed as follows, see section 2.2 of [BLL1998]):
\[\sum_{n \geq 0} \frac{1}{n!} \sum_{\sigma \in \mathfrak{S}_{n}} \operatorname{fix} F[ (G[\sigma])_{1}, (G[\sigma])_{2}, \ldots ] \, p_{1}^{\sigma_{1}} p_{2}^{\sigma_{2}} \cdots.\]Warning
The operation \(f \Box g\) only makes sense when \(g\) corresponds to a permutation representation, i.e., a group action.
EXAMPLES:
The species \(G\) of simple graphs can be expressed in terms of a functorial composition: \(G = \mathfrak{p} \Box \mathfrak{p}_{2}\), where \(\mathfrak{p}\) is the
SubsetSpecies.:sage: # needs sage.modules sage: R.<q> = QQ[] sage: h = SymmetricFunctions(R).h() sage: m = SymmetricFunctions(R).m() sage: L = LazySymmetricFunctions(m) sage: P = L(lambda n: sum(q^k*h[n-k]*h[k] for k in range(n+1))) sage: P2 = L(lambda n: h[2]*h[n-2], valuation=2) sage: P.functorial_composition(P2)[:4] # needs sage.libs.pari [m[], m[1], (q+1)*m[1, 1] + (q+1)*m[2], (q^3+3*q^2+3*q+1)*m[1, 1, 1] + (q^3+2*q^2+2*q+1)*m[2, 1] + (q^3+q^2+q+1)*m[3]]
>>> from sage.all import * >>> # needs sage.modules >>> R = QQ['q']; (q,) = R._first_ngens(1) >>> h = SymmetricFunctions(R).h() >>> m = SymmetricFunctions(R).m() >>> L = LazySymmetricFunctions(m) >>> P = L(lambda n: sum(q**k*h[n-k]*h[k] for k in range(n+Integer(1)))) >>> P2 = L(lambda n: h[Integer(2)]*h[n-Integer(2)], valuation=Integer(2)) >>> P.functorial_composition(P2)[:Integer(4)] # needs sage.libs.pari [m[], m[1], (q+1)*m[1, 1] + (q+1)*m[2], (q^3+3*q^2+3*q+1)*m[1, 1, 1] + (q^3+2*q^2+2*q+1)*m[2, 1] + (q^3+q^2+q+1)*m[3]]
# needs sage.modules R.<q> = QQ[] h = SymmetricFunctions(R).h() m = SymmetricFunctions(R).m() L = LazySymmetricFunctions(m) P = L(lambda n: sum(q^k*h[n-k]*h[k] for k in range(n+1))) P2 = L(lambda n: h[2]*h[n-2], valuation=2) P.functorial_composition(P2)[:4] # needs sage.libs.pari
For example, there are:
sage: P.functorial_composition(P2)[4].coefficient([4])[3] # needs sage.libs.pari sage.modules 3
>>> from sage.all import * >>> P.functorial_composition(P2)[Integer(4)].coefficient([Integer(4)])[Integer(3)] # needs sage.libs.pari sage.modules 3
P.functorial_composition(P2)[4].coefficient([4])[3] # needs sage.libs.pari sage.modules
unlabelled graphs on 4 vertices and 3 edges, and:
sage: P.functorial_composition(P2)[4].coefficient([2,2])[3] # needs sage.libs.pari sage.modules 8
>>> from sage.all import * >>> P.functorial_composition(P2)[Integer(4)].coefficient([Integer(2),Integer(2)])[Integer(3)] # needs sage.libs.pari sage.modules 8
P.functorial_composition(P2)[4].coefficient([2,2])[3] # needs sage.libs.pari sage.modules
labellings of their vertices with two 1s and two 2s.
The symmetric function \(h_1 \sum_n h_n\) is the neutral element with respect to functorial composition:
sage: # needs sage.modules sage: p = SymmetricFunctions(QQ).p() sage: h = SymmetricFunctions(QQ).h() sage: e = SymmetricFunctions(QQ).e() sage: L = LazySymmetricFunctions(h) sage: H = L(lambda n: h[n]) sage: Ep = p[1]*H.derivative_with_respect_to_p1(); Ep h[1] + (h[1,1]) + (h[2,1]) + (h[3,1]) + (h[4,1]) + (h[5,1]) + O^7 sage: f = L(lambda n: h[n-n//2, n//2]) sage: f - Ep.functorial_composition(f) # needs sage.libs.pari O^7
>>> from sage.all import * >>> # needs sage.modules >>> p = SymmetricFunctions(QQ).p() >>> h = SymmetricFunctions(QQ).h() >>> e = SymmetricFunctions(QQ).e() >>> L = LazySymmetricFunctions(h) >>> H = L(lambda n: h[n]) >>> Ep = p[Integer(1)]*H.derivative_with_respect_to_p1(); Ep h[1] + (h[1,1]) + (h[2,1]) + (h[3,1]) + (h[4,1]) + (h[5,1]) + O^7 >>> f = L(lambda n: h[n-n//Integer(2), n//Integer(2)]) >>> f - Ep.functorial_composition(f) # needs sage.libs.pari O^7
# needs sage.modules p = SymmetricFunctions(QQ).p() h = SymmetricFunctions(QQ).h() e = SymmetricFunctions(QQ).e() L = LazySymmetricFunctions(h) H = L(lambda n: h[n]) Ep = p[1]*H.derivative_with_respect_to_p1(); Ep f = L(lambda n: h[n-n//2, n//2]) f - Ep.functorial_composition(f) # needs sage.libs.pari
The symmetric function \(\sum_n h_n\) is a left absorbing element:
sage: # needs sage.modules sage: H.functorial_composition(f) - H O^7
>>> from sage.all import * >>> # needs sage.modules >>> H.functorial_composition(f) - H O^7
# needs sage.modules H.functorial_composition(f) - H
The functorial composition distributes over the sum:
sage: # needs sage.modules sage: F1 = L(lambda n: h[n]) sage: F2 = L(lambda n: e[n]) sage: f1 = F1.functorial_composition(f) sage: f2 = F2.functorial_composition(f) sage: (F1 + F2).functorial_composition(f) - f1 - f2 # long time O^7
>>> from sage.all import * >>> # needs sage.modules >>> F1 = L(lambda n: h[n]) >>> F2 = L(lambda n: e[n]) >>> f1 = F1.functorial_composition(f) >>> f2 = F2.functorial_composition(f) >>> (F1 + F2).functorial_composition(f) - f1 - f2 # long time O^7
# needs sage.modules F1 = L(lambda n: h[n]) F2 = L(lambda n: e[n]) f1 = F1.functorial_composition(f) f2 = F2.functorial_composition(f) (F1 + F2).functorial_composition(f) - f1 - f2 # long time
- is_unit()[source]¶
Return whether this element is a unit in the ring.
EXAMPLES:
sage: # needs sage.modules sage: m = SymmetricFunctions(ZZ).m() sage: L = LazySymmetricFunctions(m) sage: L(2*m[1]).is_unit() False sage: L(-1 + 2*m[1]).is_unit() True sage: L(2 + m[1]).is_unit() False sage: m = SymmetricFunctions(QQ).m() sage: L = LazySymmetricFunctions(m) sage: L(2 + 3*m[1]).is_unit() True
>>> from sage.all import * >>> # needs sage.modules >>> m = SymmetricFunctions(ZZ).m() >>> L = LazySymmetricFunctions(m) >>> L(Integer(2)*m[Integer(1)]).is_unit() False >>> L(-Integer(1) + Integer(2)*m[Integer(1)]).is_unit() True >>> L(Integer(2) + m[Integer(1)]).is_unit() False >>> m = SymmetricFunctions(QQ).m() >>> L = LazySymmetricFunctions(m) >>> L(Integer(2) + Integer(3)*m[Integer(1)]).is_unit() True
# needs sage.modules m = SymmetricFunctions(ZZ).m() L = LazySymmetricFunctions(m) L(2*m[1]).is_unit() L(-1 + 2*m[1]).is_unit() L(2 + m[1]).is_unit() m = SymmetricFunctions(QQ).m() L = LazySymmetricFunctions(m) L(2 + 3*m[1]).is_unit()
- legendre_transform()[source]¶
Return the Legendre transform of
self.Given a symmetric function \(f\) of valuation 2, the Legendre transform of \(f\) is the unique symmetric function \(g\) of valuation 2 over the same base ring, such that
\[g \circ \partial_{p_1} f + f = p_1 \partial_{p_1} f.\]This implies that the derivatives of \(f\) and \(g\) with respect to \(p_1\) are inverses of each other with respect to plethystic substitution.
The Legendre transform is an involution.
See also
EXAMPLES:
sage: p = SymmetricFunctions(QQ).p() sage: s = SymmetricFunctions(QQ).s() sage: lp = LazySymmetricFunctions(p) sage: A = lp(s([2])) sage: A.legendre_transform() (1/2*p[1,1]-1/2*p[2]) + O^9 sage: def asso(n): ....: return p.sum_of_terms((Partition([d] * (n // d)), ....: euler_phi(d) / n) for d in divisors(n)) sage: A = lp(asso, valuation=2) sage: A.legendre_transform()[:5] [1/2*p[1, 1] - 1/2*p[2], -1/3*p[1, 1, 1] - 2/3*p[3], 1/4*p[1, 1, 1, 1] + 1/4*p[2, 2] - 1/2*p[4]]
>>> from sage.all import * >>> p = SymmetricFunctions(QQ).p() >>> s = SymmetricFunctions(QQ).s() >>> lp = LazySymmetricFunctions(p) >>> A = lp(s([Integer(2)])) >>> A.legendre_transform() (1/2*p[1,1]-1/2*p[2]) + O^9 >>> def asso(n): ... return p.sum_of_terms((Partition([d] * (n // d)), ... euler_phi(d) / n) for d in divisors(n)) >>> A = lp(asso, valuation=Integer(2)) >>> A.legendre_transform()[:Integer(5)] [1/2*p[1, 1] - 1/2*p[2], -1/3*p[1, 1, 1] - 2/3*p[3], 1/4*p[1, 1, 1, 1] + 1/4*p[2, 2] - 1/2*p[4]]
p = SymmetricFunctions(QQ).p() s = SymmetricFunctions(QQ).s() lp = LazySymmetricFunctions(p) A = lp(s([2])) A.legendre_transform() def asso(n): return p.sum_of_terms((Partition([d] * (n // d)), euler_phi(d) / n) for d in divisors(n)) A = lp(asso, valuation=2) A.legendre_transform()[:5]
- plethysm(*args)[source]¶
Return the composition of
selfwithg.The arity of
selfmust be equal to the number of arguments provided.Given a lazy symmetric function \(f\) of arity \(n\) and a tuple of lazy symmetric functions \(g = (g_1,\dots, g_n)\) over the same base ring, the composition (or plethysm) \((f \circ g)\) is defined if and only if for each \(1\leq i\leq n\):
\(g_i = 0\), or
setting all alphabets except the \(i\)-th in \(f\) to zero yields a symmetric function with only finitely many nonzero coefficients, or
\(\mathrm{val}(g) > 0\).
If \(f\) is a univariate ‘exact’ lazy symmetric function, we can check whether \(f\) has only finitely many nonzero coefficients. However, if \(f\) has larger arity, we have no way to test whether setting all but one alphabets of \(f\) to zero yields a polynomial, except if \(f\) itself is ‘exact’ and therefore a symmetric function with only finitely many nonzero coefficients.
INPUT:
g– other (lazy) symmetric functions
Todo
Allow specification of degree one elements.
EXAMPLES:
sage: # needs sage.modules sage: P.<q> = QQ[] sage: s = SymmetricFunctions(P).s() sage: L = LazySymmetricFunctions(s) sage: f = s[2] sage: g = s[3] sage: L(f)(L(g)) - L(f(g)) 0 sage: f = s[2] + s[2,1] sage: g = s[1] + s[2,2] sage: L(f)(L(g)) - L(f(g)) 0 sage: L(f)(g) - L(f(g)) 0 sage: f = s[2] + s[2,1] sage: g = s[1] + s[2,2] sage: L(f)(L(q*g)) - L(f(q*g)) 0
>>> from sage.all import * >>> # needs sage.modules >>> P = QQ['q']; (q,) = P._first_ngens(1) >>> s = SymmetricFunctions(P).s() >>> L = LazySymmetricFunctions(s) >>> f = s[Integer(2)] >>> g = s[Integer(3)] >>> L(f)(L(g)) - L(f(g)) 0 >>> f = s[Integer(2)] + s[Integer(2),Integer(1)] >>> g = s[Integer(1)] + s[Integer(2),Integer(2)] >>> L(f)(L(g)) - L(f(g)) 0 >>> L(f)(g) - L(f(g)) 0 >>> f = s[Integer(2)] + s[Integer(2),Integer(1)] >>> g = s[Integer(1)] + s[Integer(2),Integer(2)] >>> L(f)(L(q*g)) - L(f(q*g)) 0
# needs sage.modules P.<q> = QQ[] s = SymmetricFunctions(P).s() L = LazySymmetricFunctions(s) f = s[2] g = s[3] L(f)(L(g)) - L(f(g)) f = s[2] + s[2,1] g = s[1] + s[2,2] L(f)(L(g)) - L(f(g)) L(f)(g) - L(f(g)) f = s[2] + s[2,1] g = s[1] + s[2,2] L(f)(L(q*g)) - L(f(q*g))
The Frobenius character of the permutation action on set partitions is a plethysm:
sage: # needs sage.modules sage: s = SymmetricFunctions(QQ).s() sage: S = LazySymmetricFunctions(s) sage: E1 = S(lambda n: s[n], valuation=1) sage: E = 1 + E1 sage: P = E(E1) sage: P[:5] [s[], s[1], 2*s[2], s[2, 1] + 3*s[3], 2*s[2, 2] + 2*s[3, 1] + 5*s[4]]
>>> from sage.all import * >>> # needs sage.modules >>> s = SymmetricFunctions(QQ).s() >>> S = LazySymmetricFunctions(s) >>> E1 = S(lambda n: s[n], valuation=Integer(1)) >>> E = Integer(1) + E1 >>> P = E(E1) >>> P[:Integer(5)] [s[], s[1], 2*s[2], s[2, 1] + 3*s[3], 2*s[2, 2] + 2*s[3, 1] + 5*s[4]]
# needs sage.modules s = SymmetricFunctions(QQ).s() S = LazySymmetricFunctions(s) E1 = S(lambda n: s[n], valuation=1) E = 1 + E1 P = E(E1) P[:5]
The plethysm with a tensor product is also implemented:
sage: # needs sage.modules sage: s = SymmetricFunctions(QQ).s() sage: X = tensor([s[1],s[[]]]) sage: Y = tensor([s[[]],s[1]]) sage: S = LazySymmetricFunctions(s) sage: S2 = LazySymmetricFunctions(tensor([s, s])) sage: A = S(s[1,1,1]) sage: B = S2(X+Y) sage: A(B) # needs lrcalc_python (s[]#s[1,1,1]+s[1]#s[1,1]+s[1,1]#s[1]+s[1,1,1]#s[]) sage: H = S(lambda n: s[n]) # needs sage.modules sage: H(S2(X*Y)) # needs lrcalc_python sage.modules (s[]#s[]) + (s[1]#s[1]) + (s[1,1]#s[1,1]+s[2]#s[2]) + (s[1,1,1]#s[1,1,1]+s[2,1]#s[2,1]+s[3]#s[3]) + O^7 sage: H(S2(X+Y)) # needs sage.modules (s[]#s[]) + (s[]#s[1]+s[1]#s[]) + (s[]#s[2]+s[1]#s[1]+s[2]#s[]) + (s[]#s[3]+s[1]#s[2]+s[2]#s[1]+s[3]#s[]) + (s[]#s[4]+s[1]#s[3]+s[2]#s[2]+s[3]#s[1]+s[4]#s[]) + (s[]#s[5]+s[1]#s[4]+s[2]#s[3]+s[3]#s[2]+s[4]#s[1]+s[5]#s[]) + (s[]#s[6]+s[1]#s[5]+s[2]#s[4]+s[3]#s[3]+s[4]#s[2]+s[5]#s[1]+s[6]#s[]) + O^7
>>> from sage.all import * >>> # needs sage.modules >>> s = SymmetricFunctions(QQ).s() >>> X = tensor([s[Integer(1)],s[[]]]) >>> Y = tensor([s[[]],s[Integer(1)]]) >>> S = LazySymmetricFunctions(s) >>> S2 = LazySymmetricFunctions(tensor([s, s])) >>> A = S(s[Integer(1),Integer(1),Integer(1)]) >>> B = S2(X+Y) >>> A(B) # needs lrcalc_python (s[]#s[1,1,1]+s[1]#s[1,1]+s[1,1]#s[1]+s[1,1,1]#s[]) >>> H = S(lambda n: s[n]) # needs sage.modules >>> H(S2(X*Y)) # needs lrcalc_python sage.modules (s[]#s[]) + (s[1]#s[1]) + (s[1,1]#s[1,1]+s[2]#s[2]) + (s[1,1,1]#s[1,1,1]+s[2,1]#s[2,1]+s[3]#s[3]) + O^7 >>> H(S2(X+Y)) # needs sage.modules (s[]#s[]) + (s[]#s[1]+s[1]#s[]) + (s[]#s[2]+s[1]#s[1]+s[2]#s[]) + (s[]#s[3]+s[1]#s[2]+s[2]#s[1]+s[3]#s[]) + (s[]#s[4]+s[1]#s[3]+s[2]#s[2]+s[3]#s[1]+s[4]#s[]) + (s[]#s[5]+s[1]#s[4]+s[2]#s[3]+s[3]#s[2]+s[4]#s[1]+s[5]#s[]) + (s[]#s[6]+s[1]#s[5]+s[2]#s[4]+s[3]#s[3]+s[4]#s[2]+s[5]#s[1]+s[6]#s[]) + O^7
# needs sage.modules s = SymmetricFunctions(QQ).s() X = tensor([s[1],s[[]]]) Y = tensor([s[[]],s[1]]) S = LazySymmetricFunctions(s) S2 = LazySymmetricFunctions(tensor([s, s])) A = S(s[1,1,1]) B = S2(X+Y) A(B) # needs lrcalc_python H = S(lambda n: s[n]) # needs sage.modules H(S2(X*Y)) # needs lrcalc_python sage.modules H(S2(X+Y)) # needs sage.modules
- plethystic_inverse()[source]¶
Return the compositional inverse of
self.Given a symmetric function \(f\), the compositional inverse is a symmetric function \(g\) over the same base ring, such that \(f \circ g = p_1\). Thus, it is the inverse with respect to plethystic substitution.
The compositional inverse exists if and only if:
\(\mathrm{val}(f) = 1\), or
\(f = a + b p_1\) with \(a, b \neq 0\).
See also
EXAMPLES:
sage: # needs sage.modules sage: h = SymmetricFunctions(QQ).h() sage: L = LazySymmetricFunctions(h) sage: f = L(lambda n: h[n]) - 1 sage: f(f.revert()) h[1] + O^8
>>> from sage.all import * >>> # needs sage.modules >>> h = SymmetricFunctions(QQ).h() >>> L = LazySymmetricFunctions(h) >>> f = L(lambda n: h[n]) - Integer(1) >>> f(f.revert()) h[1] + O^8
# needs sage.modules h = SymmetricFunctions(QQ).h() L = LazySymmetricFunctions(h) f = L(lambda n: h[n]) - 1 f(f.revert())
ALGORITHM:
Let \(F\) be a symmetric function with valuation \(1\), i.e., whose constant term vanishes and whose degree one term equals \(b p_1\). Then
\[(F - b p_1) \circ G = F \circ G - b p_1 \circ G = p_1 - b G,\]and therefore \(G = (p_1 - (F - b p_1) \circ G) / b\), which allows recursive computation of \(G\).
See also
The compositional inverse \(\Omega\) of the symmetric function \(h_1 + h_2 + \dots\) can be handled much more efficiently using specialized methods. See
LogarithmCycleIndexSeries()AUTHORS:
Andrew Gainer-Dewar
Martin Rubey
- revert()[source]¶
Return the compositional inverse of
self.Given a symmetric function \(f\), the compositional inverse is a symmetric function \(g\) over the same base ring, such that \(f \circ g = p_1\). Thus, it is the inverse with respect to plethystic substitution.
The compositional inverse exists if and only if:
\(\mathrm{val}(f) = 1\), or
\(f = a + b p_1\) with \(a, b \neq 0\).
See also
EXAMPLES:
sage: # needs sage.modules sage: h = SymmetricFunctions(QQ).h() sage: L = LazySymmetricFunctions(h) sage: f = L(lambda n: h[n]) - 1 sage: f(f.revert()) h[1] + O^8
>>> from sage.all import * >>> # needs sage.modules >>> h = SymmetricFunctions(QQ).h() >>> L = LazySymmetricFunctions(h) >>> f = L(lambda n: h[n]) - Integer(1) >>> f(f.revert()) h[1] + O^8
# needs sage.modules h = SymmetricFunctions(QQ).h() L = LazySymmetricFunctions(h) f = L(lambda n: h[n]) - 1 f(f.revert())
ALGORITHM:
Let \(F\) be a symmetric function with valuation \(1\), i.e., whose constant term vanishes and whose degree one term equals \(b p_1\). Then
\[(F - b p_1) \circ G = F \circ G - b p_1 \circ G = p_1 - b G,\]and therefore \(G = (p_1 - (F - b p_1) \circ G) / b\), which allows recursive computation of \(G\).
See also
The compositional inverse \(\Omega\) of the symmetric function \(h_1 + h_2 + \dots\) can be handled much more efficiently using specialized methods. See
LogarithmCycleIndexSeries()AUTHORS:
Andrew Gainer-Dewar
Martin Rubey
- suspension()[source]¶
Return the suspension of
self.This is an involution, that maps the homogeneous component \(f_n\) of degree \(n\) to \((-1)^{n - 1} \omega(f_n)\), where \(omega\) is the usual involution of symmetric functions.
EXAMPLES:
sage: s = SymmetricFunctions(QQ).s() sage: ls = LazySymmetricFunctions(s) sage: f = ls(lambda n: s([n]), valuation=1) sage: g = f.revert().suspension(); g s[1] + (s[1,1]) + (s[2,1]) + (s[2,1,1]+s[3,1]) + ... sage: g.revert().suspension() s[1] + s[2] + s[3] + s[4] + s[5] + ...
>>> from sage.all import * >>> s = SymmetricFunctions(QQ).s() >>> ls = LazySymmetricFunctions(s) >>> f = ls(lambda n: s([n]), valuation=Integer(1)) >>> g = f.revert().suspension(); g s[1] + (s[1,1]) + (s[2,1]) + (s[2,1,1]+s[3,1]) + ... >>> g.revert().suspension() s[1] + s[2] + s[3] + s[4] + s[5] + ...
s = SymmetricFunctions(QQ).s() ls = LazySymmetricFunctions(s) f = ls(lambda n: s([n]), valuation=1) g = f.revert().suspension(); g g.revert().suspension()
- symmetric_function(degree=None)[source]¶
Return
selfas a symmetric function ifselfis actually so.INPUT:
degree–Noneor an integer
OUTPUT:
If
degreeis notNone, the terms of the series of degree greater thandegreeare first truncated. IfdegreeisNoneand the series is not a polynomial polynomial, aValueErroris raised.EXAMPLES:
sage: # needs sage.modules sage: s = SymmetricFunctions(QQ).s() sage: S = LazySymmetricFunctions(s) sage: elt = S(s[2]) sage: elt.symmetric_function() s[2]
>>> from sage.all import * >>> # needs sage.modules >>> s = SymmetricFunctions(QQ).s() >>> S = LazySymmetricFunctions(s) >>> elt = S(s[Integer(2)]) >>> elt.symmetric_function() s[2]
# needs sage.modules s = SymmetricFunctions(QQ).s() S = LazySymmetricFunctions(s) elt = S(s[2]) elt.symmetric_function()