ToGrammarLeftRG.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 <grammar/Regular/LeftRG.h>
#include <automaton/FSM/NFA.h>
#include <automaton/FSM/DFA.h>
 
#include <alib/map>
#include <common/createUnique.hpp>
 
#include <alphabet/InitialSymbol.h>
 
namespace automaton {
 
namespace convert {
 
class ToGrammarLeftRG {
public:
    template < class T >
    requires isDFA < T > || isNFA < T >
    static grammar::LeftRG < typename T::SymbolType, typename T::StateType > convert ( const T & automaton );
 
};
 
template < class T >
requires isDFA < T > || isNFA < T >
grammar::LeftRG < typename T::SymbolType, typename T::StateType > ToGrammarLeftRG::convert ( const T & automaton ) {
    using SymbolType = typename T::SymbolType;
    using StateType = typename T::StateType;
 
    // step 2
    grammar::LeftRG < SymbolType, StateType > grammar(alphabet::InitialSymbol::instance < StateType > ( ) );
 
    // step 1
    grammar.setTerminalAlphabet ( automaton.getInputAlphabet ( ) );
 
    for ( const auto & state : automaton.getStates ( ) ) {
        grammar.addNonterminalSymbol ( state );
    }
 
    // step 3 - create set of P in G
    for ( const auto & transition : automaton.getTransitions ( ) ) {
        const StateType & from = transition.first.first;
        const SymbolType & input = transition.first.second;
        const StateType & to = transition.second;
 
        // 3a
        grammar.addRule ( to, ext::make_pair ( from, input ) );
 
        if ( automaton.getFinalStates ( ).contains ( to ) )
            grammar.addRule ( grammar.getInitialSymbol ( ), ext::make_pair ( from, input ) );
 
        if ( automaton.getInitialState ( ) == from ) {
            grammar.addRule ( to, input );
 
            if ( automaton.getFinalStates ( ).contains ( to ) )
                grammar.addRule ( grammar.getInitialSymbol ( ), input );
        }
    }
 
    if ( automaton.getFinalStates ( ).contains ( automaton.getInitialState ( ) ) )
        grammar.setGeneratesEpsilon ( true );
 
    return grammar;
}
 
} /* namespace convert */
 
} /* namespace automaton */