ToGrammarLeftRG.h

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#pragma once
 
#include <grammar/Regular/LeftRG.h>
#include <grammar/Regular/RightRG.h>
 
#include <common/createUnique.hpp>
 
namespace grammar {
 
namespace convert {
 
class ToGrammarLeftRG {
public:
    template < class TerminalSymbolType, class NonterminalSymbolType >
    static grammar::LeftRG < TerminalSymbolType, NonterminalSymbolType > convert(const grammar::RightRG < TerminalSymbolType, NonterminalSymbolType > & grammar);
};
 
template < class TerminalSymbolType, class NonterminalSymbolType >
grammar::LeftRG < TerminalSymbolType, NonterminalSymbolType > ToGrammarLeftRG::convert(const grammar::RightRG < TerminalSymbolType, NonterminalSymbolType > & grammar) {
    // 1.
    NonterminalSymbolType s = common::createUnique( grammar.getInitialSymbol( ), grammar.getNonterminalAlphabet(), grammar.getTerminalAlphabet() );
 
    grammar::LeftRG < TerminalSymbolType, NonterminalSymbolType > lrg(s);
 
    for(const auto & nonterminalSymbol : grammar.getNonterminalAlphabet()) {
        lrg.addNonterminalSymbol( nonterminalSymbol );
    }
 
    lrg.setTerminalAlphabet( grammar.getTerminalAlphabet( ) );
    lrg.setGeneratesEpsilon( grammar.getGeneratesEpsilon( ) );
 
    // 2.
    for( const auto & rule : grammar.getRules( ) ) {
        const NonterminalSymbolType & lhs = rule.first;
 
        for ( const auto & ruleRHS : rule.second ) {
            if ( ruleRHS.template is < ext::pair < TerminalSymbolType, NonterminalSymbolType > > ( ) ) {
                const ext::pair < TerminalSymbolType, NonterminalSymbolType > & rhs = ruleRHS.template get < ext::pair < TerminalSymbolType, NonterminalSymbolType > > ( );
 
                ext::pair<NonterminalSymbolType, TerminalSymbolType> rightSide = ext::make_pair ( lhs, rhs.first );
                lrg.addRule( rhs.second, std::move ( rightSide ) );
 
                if( lhs == grammar.getInitialSymbol( ) )
                    lrg.addRule( rhs.second, rhs.first );
            } else {
                const TerminalSymbolType & rhs = ruleRHS.template get < TerminalSymbolType > ( );
 
                ext::pair<NonterminalSymbolType, TerminalSymbolType> rightSide = ext::make_pair ( lhs, rhs );
                lrg.addRule ( lrg.getInitialSymbol ( ), std::move ( rightSide ) );
 
                if ( lhs == grammar.getInitialSymbol ( ) )
                    lrg.addRule( lrg.getInitialSymbol ( ), rhs );
            }
        }
    }
 
    return lrg;
}
 
} /* namespace convert */
 
} /* namespace grammar */