visit.h

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#pragma once
 
#include "algorithm/impl.h"
 
#include <tuple>
#include <variant>
 
namespace emlabcpp
{
 
template < typename Visitor, typename Variant >
decltype( auto ) visit_index( Visitor&& vis, Variant const& var )
{
        return impl::index_switch< 0, std::variant_size_v< std::decay_t< Variant > > >(
            var.index(), std::forward< Visitor >( vis ) );
}
 
template < typename Visitor, typename Variant >
decltype( auto ) visit( Visitor&& vis, Variant&& var )
{
        return visit_index(
            [&vis, &var]< std::size_t i >() {
                    return vis( *std::get_if< i >( &var ) );
            },
            std::forward< Variant >( var ) );
}
 
template < typename Visitor, typename Variant >
decltype( auto ) apply_on_visit( Visitor&& vis, Variant&& var )
{
        return emlabcpp::visit(
            [&vis]< typename Item >( Item&& item ) -> decltype( auto ) {
                    return std::apply(
                        [&vis]< typename... Vals >( Vals&&... vals ) -> decltype( auto ) {
                                return vis( std::forward< Vals >( vals )... );
                        },
                        std::forward< Item >( item ) );
            },
            std::forward< Variant >( var ) );
}
 
}  // namespace emlabcpp