1// Copyright 2017, 2021 Peter Dimov.
2// Distributed under the Boost Software License, Version 1.0.
3// https://www.boost.org/LICENSE_1_0.txt
4
5#include <boost/variant2/variant.hpp>
6#include <boost/core/lightweight_test.hpp>
7#include <boost/core/lightweight_test_trait.hpp>
8#include <boost/mp11.hpp>
9#include <boost/config.hpp>
10
11using namespace boost::variant2;
12using boost::mp11::mp_int;
13
14struct X
15{
16};
17
18struct F1
19{
20 int operator()( X& ) const { return 1; }
21 int operator()( X const& ) const { return 2; }
22 int operator()( X&& ) const { return 3; }
23 int operator()( X const&& ) const { return 4; }
24};
25
26struct F2
27{
28 mp_int<1> operator()( X& ) const { return {}; }
29 mp_int<2> operator()( X const& ) const { return {}; }
30 mp_int<3> operator()( X&& ) const { return {}; }
31 mp_int<4> operator()( X const&& ) const { return {}; }
32};
33
34int main()
35{
36 {
37 variant<int, int, float> v;
38
39 visit_by_index( v,
40 f: []( int& x ){ BOOST_TEST_EQ( x, 0 ); },
41 f: []( int& ){ BOOST_ERROR( "incorrect alternative" ); },
42 f: []( float& ){ BOOST_ERROR( "incorrect alternative" ); } );
43 }
44
45 {
46 variant<int const, int, float const> v( in_place_index_t<0>(), 1 );
47
48 visit_by_index( v,
49 f: []( int const& x ){ BOOST_TEST_EQ( x, 1 ); },
50 f: []( int& ){ BOOST_ERROR( "incorrect alternative" ); },
51 f: []( float const& ){ BOOST_ERROR( "incorrect alternative" ); } );
52 }
53
54 {
55 variant<int, int, float> const v( in_place_index_t<1>(), 2 );
56
57 visit_by_index( v,
58 f: []( int const& ){ BOOST_ERROR( "incorrect alternative" ); },
59 f: []( int const& x ){ BOOST_TEST_EQ( x, 2 ); },
60 f: []( float const& ){ BOOST_ERROR( "incorrect alternative" ); } );
61 }
62
63 {
64 variant<int const, int, float const> const v( 3.14f );
65
66 visit_by_index( v,
67 f: []( int const& ){ BOOST_ERROR( "incorrect alternative" ); },
68 f: []( int const& ){ BOOST_ERROR( "incorrect alternative" ); },
69 f: []( float const& x ){ BOOST_TEST_EQ( x, 3.14f ); } );
70 }
71
72 {
73 variant<int, float> const v( 7 );
74
75 auto r = visit_by_index( v,
76 f: []( int const& x ) -> double { return x; },
77 f: []( float const& x ) -> double { return x; } );
78
79 BOOST_TEST_TRAIT_SAME( decltype(r), double );
80 BOOST_TEST_EQ( r, 7.0 );
81 }
82
83 {
84 variant<int, float> const v( 2.0f );
85
86 auto r = visit_by_index( v,
87 f: []( int const& x ) { return x + 0.0; },
88 f: []( float const& x ) { return x + 0.0; } );
89
90 BOOST_TEST_TRAIT_SAME( decltype(r), double );
91 BOOST_TEST_EQ( r, 2.0 );
92 }
93
94 {
95 variant<int, float, double> const v( 3.0 );
96
97 auto r = visit_by_index<double>( v,
98 f: []( int const& x ) { return x; },
99 f: []( float const& x ) { return x; },
100 f: []( double const& x ) { return x; } );
101
102 BOOST_TEST_TRAIT_SAME( decltype(r), double );
103 BOOST_TEST_EQ( r, 3.0 );
104 }
105
106 {
107 variant<X> v;
108 variant<X> const cv;
109
110 F1 f1;
111
112 BOOST_TEST_EQ( visit_by_index( v, f1 ), 1 );
113 BOOST_TEST_EQ( visit_by_index( cv, f1 ), 2 );
114 BOOST_TEST_EQ( visit_by_index( std::move( v ), f1 ), 3 );
115 BOOST_TEST_EQ( visit_by_index( std::move( cv ), f1 ), 4 );
116
117 F2 f2;
118
119 BOOST_TEST_EQ( visit_by_index<int>( v, f2 ), 1 );
120 BOOST_TEST_EQ( visit_by_index<int>( cv, f2 ), 2 );
121 BOOST_TEST_EQ( visit_by_index<int>( std::move( v ), f2 ), 3 );
122 BOOST_TEST_EQ( visit_by_index<int>( std::move( cv ), f2 ), 4 );
123 }
124
125 return boost::report_errors();
126}
127

source code of boost/libs/variant2/test/variant_visit_by_index.cpp