#7191: Make Dirichlet characters work when base ring is CC
-----------------------------+----------------------------------------------
   Reporter:  bober          |          Owner:  bober     
       Type:  defect         |         Status:  needs_work
   Priority:  major          |      Milestone:  sage-4.8  
  Component:  number theory  |       Keywords:            
Work_issues:                 |       Upstream:  N/A       
   Reviewer:                 |         Author:            
     Merged:                 |   Dependencies:            
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Changes (by johanbosman):

  * status:  needs_review => needs_work


Comment:

 The NotImplementedError message should also be adjusted in the gauss_sum()
 function as you did in gauss_sum_numerical().
 {{{
 sage: G = DirichletGroup(500, base_ring=RR)
 sage: G[1].gauss_sum()
 ---------------------------------------------------------------------------
 NotImplementedError                       Traceback (most recent call
 last)
 ...
 NotImplementedError: Gauss sums only currently implemented when the base
 ring is a cyclotomic field or QQ.
 }}}

 In the function is_odd:
 {{{
        if rings.is_ComplexField(self.base_ring()):
             return abs(self(-1) - self.base_ring()(-1)) <
 1.0/self.parent().zeta_order()
 }}}
 I do not understand why the rather mysterious expression
 1.0/self.parent().zeta_order() is used.  I'd say that the difference is
 either 0 or 2, so if it's less than 1 in absolute value, this should
 already be sufficient to test numerically that it is 0.  Similarly for
 is_even().

 And now that I've put you back to work anyway, let's remove the C-style
 brackets in the if-statement in line 1616. ;).
 {{{
             if(rings.is_ComplexField(C)):
 }}}

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7191#comment:9>
Sage <http://www.sagemath.org>
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