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Add proper type deduction to visit_by_index

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This commit is contained in:
Peter Dimov
2021-09-15 01:30:09 +03:00
parent ed4bebff3d
commit 8fd9f830a9
2 changed files with 86 additions and 10 deletions
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78
test/variant_visit_by_index.cpp
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@ -4,9 +4,32 @@
#include <boost/variant2/variant.hpp>
#include <boost/core/lightweight_test.hpp>
#include <boost/core/lightweight_test_trait.hpp>
#include <boost/mp11.hpp>
#include <boost/config.hpp>
using namespace boost::variant2;
using boost::mp11::mp_int;
struct X
{
};
struct F1
{
int operator()( X& ) const { return 1; }
int operator()( X const& ) const { return 2; }
int operator()( X&& ) const { return 3; }
int operator()( X const&& ) const { return 4; }
};
struct F2
{
mp_int<1> operator()( X& ) const { return {}; }
mp_int<2> operator()( X const& ) const { return {}; }
mp_int<3> operator()( X&& ) const { return {}; }
mp_int<4> operator()( X const&& ) const { return {}; }
};
int main()
{
@ -20,7 +43,7 @@ int main()
}
{
variant<int const, int, float const> v( 1 );
variant<int const, int, float const> v( in_place_index_t<0>(), 1 );
visit_by_index( v,
[]( int const& x ){ BOOST_TEST_EQ( x, 1 ); },
@ -46,5 +69,58 @@ int main()
[]( float const& x ){ BOOST_TEST_EQ( x, 3.14f ); } );
}
{
variant<int, float> const v( 7 );
auto r = visit_by_index( v,
[]( int const& x ) -> double { return x; },
[]( float const& x ) -> double { return x; } );
BOOST_TEST_TRAIT_SAME( decltype(r), double );
BOOST_TEST_EQ( r, 7.0 );
}
{
variant<int, float> const v( 2.0f );
auto r = visit_by_index( v,
[]( int const& x ) { return x + 0.0; },
[]( float const& x ) { return x + 0.0; } );
BOOST_TEST_TRAIT_SAME( decltype(r), double );
BOOST_TEST_EQ( r, 2.0 );
}
{
variant<int, float, double> const v( 3.0 );
auto r = visit_by_index<double>( v,
[]( int const& x ) { return x; },
[]( float const& x ) { return x; },
[]( double const& x ) { return x; } );
BOOST_TEST_TRAIT_SAME( decltype(r), double );
BOOST_TEST_EQ( r, 3.0 );
}
{
variant<X> v;
variant<X> const cv;
F1 f1;
BOOST_TEST_EQ( visit_by_index( v, f1 ), 1 );
BOOST_TEST_EQ( visit_by_index( cv, f1 ), 2 );
BOOST_TEST_EQ( visit_by_index( std::move( v ), f1 ), 3 );
BOOST_TEST_EQ( visit_by_index( std::move( cv ), f1 ), 4 );
F2 f2;
BOOST_TEST_EQ( visit_by_index<int>( v, f2 ), 1 );
BOOST_TEST_EQ( visit_by_index<int>( cv, f2 ), 2 );
BOOST_TEST_EQ( visit_by_index<int>( std::move( v ), f2 ), 3 );
BOOST_TEST_EQ( visit_by_index<int>( std::move( cv ), f2 ), 4 );
}
return boost::report_errors();
}