1// Copyright Louis Dionne 2013-2022
2// Distributed under the Boost Software License, Version 1.0.
3// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
4
5#include <boost/hana/assert.hpp>
6#include <boost/hana/ext/std/integral_constant.hpp>
7#include <boost/hana/find.hpp>
8#include <boost/hana/find_if.hpp>
9#include <boost/hana/functional/compose.hpp>
10#include <boost/hana/integral_constant.hpp>
11#include <boost/hana/optional.hpp>
12#include <boost/hana/tuple.hpp>
13#include <boost/hana/type.hpp>
14
15#include <type_traits>
16namespace hana = boost::hana;
17
18
19// First get the type of the object, and then call the trait on it.
20constexpr auto is_integral = hana::compose(hana::trait<std::is_integral>, hana::typeid_);
21constexpr auto is_class = hana::compose(hana::trait<std::is_class>, hana::typeid_);
22
23static_assert(
24 hana::find_if(hana::make_tuple(1.0, 2, '3'), is_integral)
25 ==
26 hana::just(2)
27, "");
28
29BOOST_HANA_CONSTANT_CHECK(
30 hana::find_if(hana::make_tuple(1.0, 2, '3'), is_class)
31 ==
32 hana::nothing
33);
34
35BOOST_HANA_CONSTANT_CHECK(
36 hana::find(hana::make_tuple(hana::int_c<1>, hana::char_c<'c'>, hana::type_c<void>), hana::type_c<void>)
37 ==
38 hana::just(hana::type_c<void>)
39);
40
41BOOST_HANA_CONSTANT_CHECK(
42 hana::find(hana::make_tuple(hana::int_c<1>, hana::char_c<'c'>, hana::type_c<void>), hana::type_c<int>)
43 ==
44 hana::nothing
45);
46
47int main() { }
48

source code of boost/libs/hana/example/iterable/searchable.cpp