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Answer 1

+2 A:

http://www.boost.org/doc/libs/1_44_0/libs/type_traits/doc/html/boost_typetraits/reference/is_enum.html

I appreciate you want total portability and not to use boost. If you find that impractical, you might still prefer to use a simple ifdef and the following: MSDN has a similar facility on the front page of google results for c++ is_enum. On recent GNU compilers, try your luck with using std::tr1::is_enum;

Even if you don't want to use boost, you could examine it for the technique used in determination. Looks complex enough to be exclusion of all other possibilities :-/.

Tony 2010-09-15 19:10:09

@Tony I've updated my question

There is nothing we can do 2010-09-15 19:17:06

Actually, is_enum should be used with care. Some compilers don't support it correctly. See the latest version of boost: http://www.boost.org/doc/libs/1_44_0/libs/type_traits/doc/html/boost_typetraits/reference/is_enum.html

Cătălin Pitiș 2010-09-15 19:18:19

@Cătălin: "broken under Borland C++ Builder 5, and for the Metrowerks compiler prior to version 8" isn't likely to bother too many people (poor old Borland).

Tony 2010-09-15 19:23:25

@A-ha: to do it without Boost, open the Boost source and copy-paste. They have a habit of thinking hard and reviewing thoroughly, you probably won't find a better implementation.

Potatoswatter 2010-09-15 19:26:35

@Tony: You're right. However, I still see Visual Studio 6 required in some projects, so why not MW 8 or BC 5? About the same generation :)

Cătălin Pitiș 2010-09-15 19:27:16

@Potatoswatter it's not about finding better implementation. I want to learn how it is done. That's all.

There is nothing we can do 2010-09-15 19:34:43

Answer 2

+1 A:

Looking at http://www.boost.org/doc/libs/1_44_0/boost/type_traits/is_enum.hpp,

If this evaluates to true:

::boost::type_traits::ice_or<
           ::boost::is_arithmetic<T>::value
         , ::boost::is_reference<T>::value
         , ::boost::is_function<T>::value
         , is_class_or_union<T>::value
         , is_array<T>::value
      >::value

Then this base template is selected:

// Don't evaluate convertibility to int_convertible unless the type
// is non-arithmetic. This suppresses warnings with GCC.
template <bool is_typename_arithmetic_or_reference = true>
struct is_enum_helper
{
    template <typename T> struct type
    {
        BOOST_STATIC_CONSTANT(bool, value = false);
    };
};

Otherwise check if it's convertible to int:

template <>
struct is_enum_helper<false>
{
    template <typename T> struct type
       : ::boost::is_convertible<typename boost::add_reference<T>::type,::boost::detail::int_convertible>
    {
    };
};

If you want to do it as well as Boost, you'll have to define all those other traits. <type_traits> is like that.

Potatoswatter 2010-09-15 19:50:14

ansaurus

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Way to check if type is an enum.

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