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turned a complicatedcondition in enable_if into a metafun

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This commit is contained in:
Andrzej Krzemienski
2016-02-19 01:51:08 +01:00
parent 44d57a1d8b
commit 5ffa3fd2f6
1 changed files with 16 additions and 8 deletions
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24
include/boost/optional/optional.hpp
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@ -30,6 +30,7 @@
#include <boost/throw_exception.hpp> #include <boost/throw_exception.hpp>
#include <boost/type.hpp> #include <boost/type.hpp>
#include <boost/type_traits/alignment_of.hpp> #include <boost/type_traits/alignment_of.hpp>
#include <boost/type_traits/conditional.hpp>
#include <boost/type_traits/has_nothrow_constructor.hpp> #include <boost/type_traits/has_nothrow_constructor.hpp>
#include <boost/type_traits/type_with_alignment.hpp> #include <boost/type_traits/type_with_alignment.hpp>
#include <boost/type_traits/remove_const.hpp> #include <boost/type_traits/remove_const.hpp>
@ -564,6 +565,19 @@ class optional_base : public optional_tag
storage_type m_storage ; storage_type m_storage ;
} ; } ;
template <typename U>
struct is_optional_related
: boost::conditional<boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
|| boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<U>::type, none_t>::value,
boost::true_type, boost::false_type>::type
{};
template <typename, typename U>
struct is_optional_val_init_candidate
: boost::conditional<!is_optional_related<U>::value, boost::true_type, boost::false_type>::type
{};
} // namespace optional_detail } // namespace optional_detail
template<class T> template<class T>
@ -652,9 +666,7 @@ class optional : public optional_detail::optional_base<T>
template<class Expr> template<class Expr>
explicit optional ( Expr&& expr, explicit optional ( Expr&& expr,
BOOST_DEDUCED_TYPENAME boost::disable_if_c< BOOST_DEDUCED_TYPENAME boost::enable_if< optional_detail::is_optional_val_init_candidate<T, Expr> >::type* = 0
(boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value) ||
boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value >::type* = 0
) )
: base(boost::forward<Expr>(expr),boost::addressof(expr)) : base(boost::forward<Expr>(expr),boost::addressof(expr))
{} {}
@ -691,11 +703,7 @@ class optional : public optional_detail::optional_base<T>
#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
template<class Expr> template<class Expr>
BOOST_DEDUCED_TYPENAME boost::disable_if_c< BOOST_DEDUCED_TYPENAME boost::enable_if<optional_detail::is_optional_val_init_candidate<T, Expr>, optional&>::type
boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value ||
boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value,
optional&
>::type
operator= ( Expr&& expr ) operator= ( Expr&& expr )
{ {
this->assign_expr(boost::forward<Expr>(expr),boost::addressof(expr)); this->assign_expr(boost::forward<Expr>(expr),boost::addressof(expr));