#1956: implement multivariate truncated power series arithmetic
---------------------------------------------------------------------------------------------------+
   Reporter:  was                                                               
                   |       Owner:  pernici                  
       Type:  enhancement                                                       
                   |      Status:  needs_review             
   Priority:  major                                                             
                   |   Milestone:  sage-4.6.2               
  Component:  commutative algebra                                               
                   |    Keywords:  multivariate power series
     Author:  Niles Johnson                                                     
                   |    Upstream:  N/A                      
   Reviewer:  Martin Albrecht, Simon King                                       
                   |      Merged:                           
Work_issues:  multivariate series on 1 generator should remain different from a 
univariate series  |  
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Comment(by pernici):

 The method sqrt of MPowerSeries does not work because sqrt does not
 currently work for series on polynomial rings.

 In ticket #10720 nth_root is added;
 applying trac_10720_power_series_nth_root_2.patch

 the definition of nth_root for MPowerSeries is
 {{{
 sage: def nth_root(self, n):
 ....:     return self.parent(self._bg_value.nth_root(n))
 ....:
 }}}

 Examples:
 {{{
 sage: R.<x,y> = QQ[[]]
 sage: p = 1 + 2*x + 3*y + R.O(20)
 sage: nth_root(p^10,2) - p^5
 0 + O(x, y)^20
 sage: nth_root(p^10,5) - p^2
 0 + O(x, y)^20
 sage: nth_root(p^-10,2) - p^-5
 0 + O(x, y)^20
 sage: nth_root(p^-10,5) - p^-2
 0 + O(x, y)^20
 }}}

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/1956#comment:84>
Sage <http://www.sagemath.org>
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