[boost] Re: Type Traits and Test Library

From: David Abrahams (dave_at_[hidden])
Date: 2004-01-23 18:10:22

"Rozental, Gennadiy" <gennadiy.rozental_at_[hidden]> writes:

>> It causes lots of recompilation; that's really frustrating 
>> when the test could be done just as well if not better at 
>> compile-time using some kind of static assert.  
>
> Do you have any specific compile time test tools in mind? Does it worth
> reusing?

  # include <boost/type.hpp>
  # include <boost/static_assert.hpp>

  #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  template <bool>
  struct assert_apply_base;

  template <>
  struct assert_apply_base<true>
  {
      enum { value = 1 };
  };

  template <class E>
  struct assert_apply : assert_apply_base<E::value> {};

  #else
  # include <boost/mpl/if.hpp>
  # include <boost/mpl/bool.hpp>
  # include <boost/type_traits/is_same.hpp>

  template <E>
  struct assert_apply
      : boost::mpl::if_<E,boost::mpl::true_,void>::type
  {};
  #endif

  #define ASSERT_APPLY( E )                   \
     enum { BOOST_JOIN(boost_static_assert_enum_, __LINE__) \
            = assert_apply<E>::value }

  // ----------
  #include <boost/mpl/not.hpp>

  ASSERT_APPLY(is_class<Foo>);
  ASSERT_APPLY(mpl::not_<is_class<int> >);

  // etc.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com