#7644: generic power series reversion
---------------------------+------------------------------------------------
   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:               |  
---------------------------+------------------------------------------------

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>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
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