BottomOfTheStackSymbol.h

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/*
 * This file is part of Algorithms library toolkit.
 * Copyright (C) 2017 Jan Travnicek (jan.travnicek@fit.cvut.cz)
 
 * Algorithms library toolkit is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 
 * Algorithms library toolkit is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 
 * You should have received a copy of the GNU General Public License
 * along with Algorithms library toolkit.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include <object/Object.h>
#include <common/ranked_symbol.hpp>
 
namespace alphabet {
 
class BottomOfTheStackSymbol {
public:
    explicit BottomOfTheStackSymbol ( );
 
    std::strong_ordering operator <=> ( const BottomOfTheStackSymbol & ) const {
        return std::strong_ordering::equal;
    }
 
    bool operator == ( const BottomOfTheStackSymbol & ) const {
        return true;
    }
 
    friend ext::ostream & operator << ( ext::ostream & out, const BottomOfTheStackSymbol & instance );
 
    template < typename Base >
    static inline Base instance ( );
};
 
template < typename Base >
inline Base BottomOfTheStackSymbol::instance ( ) {
    if constexpr ( std::is_integral_v < Base > ) {
        return '_';
    } else if constexpr ( std::is_same_v < Base, std::string > ) {
        return std::string ( 1, BottomOfTheStackSymbol::instance < char > ( ) );
    } else if constexpr ( std::is_same_v < Base, BottomOfTheStackSymbol > ) {
        return BottomOfTheStackSymbol ( );
    } else if constexpr ( std::is_same_v < Base, object::Object > ) {
        return object::Object ( BottomOfTheStackSymbol ( ) );
    } else if constexpr ( std::is_same_v < Base, common::ranked_symbol < > > ) {
        return common::ranked_symbol < > ( BottomOfTheStackSymbol::instance < DefaultSymbolType > ( ), 0u );
    } else {
        static_assert ( std::is_same_v < Base, Base >, "Unsupported type of instance" );
    }
}
 
} /* namespace alphabet */