boost/detail/ob_type_traits.hpp

From: Brad King (brad.king_at_[hidden])
Date: 2001-01-25 09:47:18

Hello, all:

I've been digging through the type_traits package to find how various
hacks were done to support compilers like MSVC++, and I noticed a
simplification that could be made to the library.  The is_const struct
uses a static member in order to get a pointer of the appropriate type to
pass to its helper function.  This could be done with a cast of a null
pointer instead:

template <typename T>
struct is_const
{ 
private:
   static T t;
public:
   enum{ value = (sizeof(detail::yes_result)
                  == sizeof(detail::is_const_helper(&t))) };
};

could become

template <typename T>
struct is_const
{
   enum{ value = (sizeof(detail::yes_result)
     == sizeof(detail::is_const_helper(static_cast<T*>(0)))) };
};

static_cast<T*>(0) could be replaced with (T*)0 if static_cast isn't
supported by some compiler.

This seems to work fine under gcc 2.95.2 and VC++ 6.0sp4 for me.  Is there
some other compiler for which it won't work?

-Brad