#7644: generic power series reversion
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Reporter: was | Owner: AlexGhitza
Type: enhancement | Status: new
Priority: major | Milestone: sage-4.3.1
Component: algebra | Keywords:
Work_issues: | Author:
Upstream: N/A | Reviewer:
Merged: |
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Comment(by was):
{{{
The code doesn't quite run, since it references some other function
(ps_coefficient); here's an updated version which uses only built-in
functions:
def ps_inverse_Lagrange(f):
if f.valuation() != 1:
raise ValueError, "series must have valuation one for
reversion"
if f.prec() is infinity:
raise ValueError, "series must have finite precision for
reversion"
t = parent(f).gen()
h = t/f
k = 1
g = 0
for i in range(1, f.prec()):
k *= h
g += (1/i)*k.padded_list(i)[i - 1]*t^i
g += O(t^f.prec())
return g
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7644#comment:3>
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