#12489: Fix equality of combinatorial free module on non totally ordered basis
------------------------------+---------------------------------------------
   Reporter:  hivert          |          Owner:  sage-combinat                  
  
       Type:  defect          |         Status:  new                            
  
   Priority:  critical        |      Milestone:  sage-5.0                       
  
  Component:  combinatorics   |       Keywords:  CombinatorialFreeModule, 
equality
Work_issues:                  |       Upstream:  N/A                            
  
   Reviewer:  Florent Hivert  |         Author:  Nicolas Thiery                 
  
     Merged:                  |   Dependencies:                                 
  
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 The following is obviously wrong:
 {{{
 sage: F = CombinatorialFreeModule(QQ, Subsets([1,2,3]))
 sage: x = F.an_element()
 sage: x+0 == x
 False
 sage: x+F.zero() == x
 False
 }}}
 The reason is
 {{{
 sage: (x+F.zero()).terms()  # random
 [2*B[{1}], 3*B[{2}], B[{}]]
 sage: x.terms()             # random
 [2*B[{1}], B[{}], 3*B[{2}]]
 }}}

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12489>
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