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hana/example/list/foldable/find.cpp

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1.1 KiB
C++

/*
@copyright Louis Dionne 2014
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
#include <boost/hana/detail/constexpr.hpp>
#include <boost/hana/detail/static_assert.hpp>
#include <boost/hana/functional.hpp>
#include <boost/hana/list.hpp>
#include <boost/hana/maybe.hpp>
#include <boost/hana/trait.hpp>
#include <boost/hana/type.hpp>
using namespace boost::hana;
int main() {
//! [fusion]
//! @todo `compose(trait::..., decltype_)` is too verbose. Find an elegant
//! way to make this easier.
BOOST_HANA_STATIC_ASSERT(
find(compose(trait::is_integral, decltype_), list(1.0, 2)) == just(2)
);
BOOST_HANA_STATIC_ASSERT(
find(compose(trait::is_class, decltype_), list(1.0, 2)) == nothing
);
//! [fusion]
//! [mpl]
BOOST_HANA_CONSTEXPR_LAMBDA auto types = list_t<char, int, unsigned, long, unsigned long>;
BOOST_HANA_STATIC_ASSERT(find(_ == type<unsigned>, types) == just(type<unsigned>));
BOOST_HANA_STATIC_ASSERT(find(_ == type<void>, types) == nothing);
//! [mpl]
}