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No longer use fold expressions for mp_count_if to avoid compiler limits

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This commit is contained in:
Peter Dimov
2021-03-22 19:17:44 +02:00
parent 0348adbed9
commit c92d2d0b6f
1 changed files with 16 additions and 2 deletions
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18
include/boost/mp11/detail/mp_count.hpp
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@@ -90,11 +90,25 @@ namespace detail
template<class L, template<class...> class P> struct mp_count_if_impl;
#if defined( BOOST_MP11_HAS_FOLD_EXPRESSIONS ) && !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1930 )
#if defined( BOOST_MP11_HAS_CXX14_CONSTEXPR ) && !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1930 )
template<template<class...> class P, class... T> constexpr std::size_t cx_count_if()
{
constexpr bool a[] = { false, static_cast<bool>( P<T>::value )... };
std::size_t r = 0;
for( std::size_t i = 0; i < sizeof...(T); ++i )
{
r += a[ i+1 ];
}
return r;
}
template<template<class...> class L, class... T, template<class...> class P> struct mp_count_if_impl<L<T...>, P>
{
using type = mp_size_t<(mp_to_bool<P<T>>::value + ... + 0)>;
using type = mp_size_t<cx_count_if<P, T...>()>;
};
#elif !defined( BOOST_MP11_NO_CONSTEXPR )