hana/example/optional/sfinae.cpp
2017-01-07 14:14:18 -08:00

22 lines
643 B
C++

// Copyright Louis Dionne 2013-2017
// 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/assert.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/equal.hpp>
#include <boost/hana/optional.hpp>
namespace hana = boost::hana;
int main() {
BOOST_HANA_CONSTEXPR_LAMBDA auto incr = [](auto x) -> decltype(x + 1) {
return x + 1;
};
BOOST_HANA_CONSTEXPR_CHECK(hana::sfinae(incr)(1) == hana::just(2));
struct invalid { };
BOOST_HANA_CONSTANT_CHECK(hana::sfinae(incr)(invalid{}) == hana::nothing);
}