[Boost-bugs] [Boost C++ Libraries] #6495: consider implementing traits for numeric types in terms of numeric_limits

Subject: [Boost-bugs] [Boost C++ Libraries] #6495: consider implementing traits for numeric types in terms of numeric_limits
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-01-30 17:40:30

#6495: consider implementing traits for numeric types in terms of numeric_limits
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 Reporter:  ramey                                          |       Owner:  johnmaddock
     Type:  Feature Requests                               |      Status:  new        
Milestone:  To Be Determined                               |   Component:  type_traits
  Version:  Boost 1.48.0                                   |    Severity:  Problem    
 Keywords:  is_signed, is_unsigned, is_float, is_integral  |  
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 The following type traits

 is_signed, is_unsigned, is_float, is_integral, are currently implemented
 by checking against a list of numeric primitives. so far so good.

 But what happens when one specializes numeric_limits for his own new
 wizbang numeric type like big_integer, arbitrary_length integer,
 modular_integer, safe_integer, safe_float, etc. etc.  I ideally I would
 expect to see that the above type traits should "just work" but they won't
 under the current implementation.

 Note that specializing std::numeric_limits is permited by the current
 standard for one's own types (though not for types in the std namespace)
 so this is an actual problem rather than a hypothetical one.

 The would leave make_signed, make_unsigned a little bit out in the cold as
 they're implementation can't be done in terms of std::numeric_limits.

 admittedly, is_integral might not fit here as it has a very specific
 meaning, but I think my concern applies to the other ones for regardless.

 Robert Ramey

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/6495>
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