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Add support for value lists to mp_front. Refs #53.

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This commit is contained in:
Peter Dimov
2023-05-15 14:52:26 +03:00
parent 481755ce7c
commit 2c76388fdb
3 changed files with 54 additions and 1 deletions
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14
include/boost/mp11/detail/mp_front.hpp
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@@ -1,13 +1,16 @@
#ifndef BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
#define BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
// Copyright 2015-2021 Peter Dimov.
// Copyright 2015-2023 Peter Dimov.
//
// 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
#include <boost/mp11/detail/mp_value.hpp>
#include <boost/mp11/detail/config.hpp>
namespace boost
{
namespace mp11
@@ -28,6 +31,15 @@ template<template<class...> class L, class T1, class... T> struct mp_front_impl<
using type = T1;
};
#if defined(BOOST_MP11_HAS_TEMPLATE_AUTO)
template<template<auto...> class L, auto A1, auto... A> struct mp_front_impl<L<A1, A...>>
{
using type = mp_value<A1>;
};
#endif
} // namespace detail
template<class L> using mp_front = typename detail::mp_front_impl<L>::type;

1
test/Jamfile
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@@ -34,6 +34,7 @@ run mp_assign_2.cpp ;
run mp_clear.cpp ;
run mp_clear_2.cpp ;
run mp_front.cpp ;
run mp_front_2.cpp ;
run mp_pop_front.cpp ;
run mp_second.cpp ;
run mp_third.cpp ;

40
test/mp_front_2.cpp Normal file
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@@ -0,0 +1,40 @@
// Copyright 2023 Peter Dimov
// Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt
#include <boost/mp11/list.hpp>
#if !defined(BOOST_MP11_HAS_TEMPLATE_AUTO)
#pragma message("Test skipped because BOOST_MP11_HAS_TEMPLATE_AUTO is not defined")
int main() {}
#else
#include <boost/mp11/integral.hpp>
#include <boost/core/lightweight_test_trait.hpp>
template<auto... A> struct L1 {};
template<int... I> struct L2 {};
int main()
{
using boost::mp11::mp_list_v;
using boost::mp11::mp_front;
using boost::mp11::mp_first;
using boost::mp11::mp_false;
using boost::mp11::mp_int;
BOOST_TEST_TRAIT_SAME(mp_front<mp_list_v<false>>, mp_false);
BOOST_TEST_TRAIT_SAME(mp_first<mp_list_v<false>>, mp_false);
BOOST_TEST_TRAIT_SAME(mp_front<L1<-1, true>>, mp_int<-1>);
BOOST_TEST_TRAIT_SAME(mp_first<L1<-1, true>>, mp_int<-1>);
BOOST_TEST_TRAIT_SAME(mp_front<L2<0, 1>>, mp_int<0>);
BOOST_TEST_TRAIT_SAME(mp_first<L2<0, 1>>, mp_int<0>);
return boost::report_errors();
}
#endif