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Factored if_true out into boost/detail/select_type.hpp

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[SVN r8991]
This commit is contained in:
Dave Abrahams
2001-02-07 04:49:32 +00:00
parent 3cbecf5ddd
commit 8b60ca8d0a
1 changed files with 5 additions and 21 deletions
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26
include/boost/detail/numeric_traits.hpp
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@@ -49,11 +49,13 @@
// See http://www.boost.org for most recent version including documentation. // See http://www.boost.org for most recent version including documentation.
// Revision History // Revision History
// 06 Feb 2001 - Factored if_true out into boost/detail/select_type.hpp
// (David Abrahams)
// 23 Jan 2001 - Fixed logic of difference_type selection, which was // 23 Jan 2001 - Fixed logic of difference_type selection, which was
// completely wack. In the process, added digit_traits<> // completely wack. In the process, added digit_traits<>
// to compute the number of digits in intmax_t even when // to compute the number of digits in intmax_t even when
// not supplied by numeric_limits<>. // not supplied by numeric_limits<>. (David Abrahams)
// 21 Jan 2001 - Created // 21 Jan 2001 - Created (David Abrahams)
#ifndef BOOST_NUMERIC_TRAITS_HPP_DWA20001901 #ifndef BOOST_NUMERIC_TRAITS_HPP_DWA20001901
# define BOOST_NUMERIC_TRAITS_HPP_DWA20001901 # define BOOST_NUMERIC_TRAITS_HPP_DWA20001901
@@ -62,31 +64,13 @@
# include <boost/cstdint.hpp> # include <boost/cstdint.hpp>
# include <boost/static_assert.hpp> # include <boost/static_assert.hpp>
# include <boost/type_traits.hpp> # include <boost/type_traits.hpp>
# include <boost/detail/select_type.hpp>
# ifndef BOOST_NO_LIMITS # ifndef BOOST_NO_LIMITS
# include <limits> # include <limits>
# endif # endif
namespace boost { namespace detail { namespace boost { namespace detail {
// Template class if_true -- select among 2 types based on a bool constant expression
// Usage:
// typename if_true<(bool_const_expression)>::template then<true_type, false_type>::type
template <bool> struct if_true;
template <>
struct if_true<true>
{
template <class T1, class T2>
struct then { typedef T1 type; };
};
template <>
struct if_true<false>
{
template <class T1, class T2>
struct then { typedef T2 type; };
};
// Template class is_signed -- determine whether a numeric type is signed // Template class is_signed -- determine whether a numeric type is signed
// Requires that T is constructable from the literals -1 and 0. Compile-time // Requires that T is constructable from the literals -1 and 0. Compile-time
// error results if that requirement is not met (and thus signedness is not // error results if that requirement is not met (and thus signedness is not