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/chain.hpp>
7#include <boost/hana/equal.hpp>
8#include <boost/hana/optional.hpp>
9
10#include <laws/base.hpp>
11#include <support/tracked.hpp>
12namespace hana = boost::hana;
13using hana::test::ct_eq;
14
15
16struct undefined { };
17
18int main() {
19 hana::test::_injection<0> f{};
20
21 BOOST_HANA_CONSTANT_CHECK(hana::equal(
22 hana::sfinae(f)(),
23 hana::just(f())
24 ));
25
26 BOOST_HANA_CONSTANT_CHECK(hana::equal(
27 hana::sfinae(f)(ct_eq<0>{}),
28 hana::just(f(ct_eq<0>{}))
29 ));
30
31 BOOST_HANA_CONSTANT_CHECK(hana::equal(
32 hana::sfinae(f)(ct_eq<0>{}, ct_eq<1>{}),
33 hana::just(f(ct_eq<0>{}, ct_eq<1>{}))
34 ));
35
36 BOOST_HANA_CONSTANT_CHECK(hana::equal(
37 hana::sfinae(undefined{})(),
38 hana::nothing
39 ));
40
41 BOOST_HANA_CONSTANT_CHECK(hana::equal(
42 hana::sfinae(undefined{})(ct_eq<0>{}),
43 hana::nothing
44 ));
45
46 BOOST_HANA_CONSTANT_CHECK(hana::equal(
47 hana::sfinae(undefined{})(ct_eq<0>{}, ct_eq<1>{}),
48 hana::nothing
49 ));
50
51 auto incr = hana::sfinae([](auto x) -> decltype(x + 1) {
52 return x + 1;
53 });
54
55 BOOST_HANA_RUNTIME_CHECK(hana::equal(
56 incr(1),
57 hana::just(2)
58 ));
59 BOOST_HANA_CONSTANT_CHECK(hana::equal(
60 incr(undefined{}),
61 hana::nothing
62 ));
63 BOOST_HANA_RUNTIME_CHECK(hana::equal(
64 hana::chain(hana::just(1), incr),
65 hana::just(2)
66 ));
67
68 // using `sfinae` with a non-pod argument used to fail
69 hana::sfinae(undefined{})(Tracked{1});
70 hana::sfinae([t = Tracked{1}](auto) { return 1; })(Tracked{1});
71}
72

source code of boost/libs/hana/test/optional/sfinae.cpp