You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
84 lines
1.9 KiB
84 lines
1.9 KiB
// (C) Copyright David Abrahams 2002.
|
|
// (C) Copyright Jeremy Siek 2002.
|
|
// (C) Copyright Thomas Witt 2002.
|
|
// Distributed under the Boost Software License, Version 1.0. (See
|
|
// accompanying file LICENSE_1_0.txt or copy at
|
|
// http://www.boost.org/LICENSE_1_0.txt)
|
|
#ifndef BOOST_ENABLE_IF_23022003THW_HPP
|
|
#define BOOST_ENABLE_IF_23022003THW_HPP
|
|
|
|
#include <boost/detail/workaround.hpp>
|
|
#include <boost/mpl/identity.hpp>
|
|
|
|
#include <boost/iterator/detail/config_def.hpp>
|
|
|
|
//
|
|
// Boost iterators uses its own enable_if cause we need
|
|
// special semantics for deficient compilers.
|
|
// 23/02/03 thw
|
|
//
|
|
|
|
namespace boost
|
|
{
|
|
|
|
namespace iterators
|
|
{
|
|
//
|
|
// Base machinery for all kinds of enable if
|
|
//
|
|
template<bool>
|
|
struct enabled
|
|
{
|
|
template<typename T>
|
|
struct base
|
|
{
|
|
typedef T type;
|
|
};
|
|
};
|
|
|
|
//
|
|
// For compilers that don't support "Substitution Failure Is Not An Error"
|
|
// enable_if falls back to always enabled. See comments
|
|
// on operator implementation for consequences.
|
|
//
|
|
template<>
|
|
struct enabled<false>
|
|
{
|
|
template<typename T>
|
|
struct base
|
|
{
|
|
#ifdef BOOST_NO_SFINAE
|
|
|
|
typedef T type;
|
|
|
|
// This way to do it would give a nice error message containing
|
|
// invalid overload, but has the big disadvantage that
|
|
// there is no reference to user code in the error message.
|
|
//
|
|
// struct invalid_overload;
|
|
// typedef invalid_overload type;
|
|
//
|
|
#endif
|
|
};
|
|
};
|
|
|
|
|
|
template <class Cond,
|
|
class Return>
|
|
struct enable_if
|
|
# if !defined(BOOST_NO_SFINAE) && !defined(BOOST_NO_IS_CONVERTIBLE)
|
|
: enabled<(Cond::value)>::template base<Return>
|
|
# else
|
|
: mpl::identity<Return>
|
|
# endif
|
|
{
|
|
};
|
|
|
|
} // namespace iterators
|
|
|
|
} // namespace boost
|
|
|
|
#include <boost/iterator/detail/config_undef.hpp>
|
|
|
|
#endif // BOOST_ENABLE_IF_23022003THW_HPP
|