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using Implab;
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using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace Implab.Automaton.RegularExpressions {
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/// <summary>
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/// Базовый абстрактный класс. Грамматика, позволяет формулировать выражения над алфавитом типа <c>char</c>.
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/// </summary>
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public abstract class Grammar<TSymbol, TTag> {
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protected abstract IAlphabetBuilder<TSymbol> AlphabetBuilder {
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get;
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}
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protected SymbolToken<TTag> UnclassifiedToken() {
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return new SymbolToken<TTag>(DFAConst.UNCLASSIFIED_INPUT);
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}
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protected void DefineAlphabet(IEnumerable<TSymbol> alphabet) {
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Safe.ArgumentNotNull(alphabet, "alphabet");
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foreach (var ch in alphabet)
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AlphabetBuilder.DefineSymbol(ch);
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}
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protected Token<TTag> SymbolToken(TSymbol symbol) {
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return Token<TTag>.New(TranslateOrAdd(symbol));
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}
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protected Token<TTag> SymbolToken(IEnumerable<TSymbol> symbols) {
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Safe.ArgumentNotNull(symbols, "symbols");
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return Token<TTag>.New(TranslateOrAdd(symbols).ToArray());
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}
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protected Token<TTag> SymbolSetToken(params TSymbol[] set) {
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return SymbolToken(set);
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}
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int TranslateOrAdd(TSymbol ch) {
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var t = AlphabetBuilder.Translate(ch);
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if (t == DFAConst.UNCLASSIFIED_INPUT)
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t = AlphabetBuilder.DefineSymbol(ch);
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return t;
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}
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IEnumerable<int> TranslateOrAdd(IEnumerable<TSymbol> symbols) {
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return symbols.Distinct().Select(TranslateOrAdd);
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}
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int TranslateOrDie(TSymbol ch) {
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var t = AlphabetBuilder.Translate(ch);
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if (t == DFAConst.UNCLASSIFIED_INPUT)
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throw new ApplicationException(String.Format("Symbol '{0}' is UNCLASSIFIED", ch));
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return t;
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}
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IEnumerable<int> TranslateOrDie(IEnumerable<TSymbol> symbols) {
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return symbols.Distinct().Select(TranslateOrDie);
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}
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protected Token<TTag> SymbolTokenExcept(IEnumerable<TSymbol> symbols) {
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Safe.ArgumentNotNull(symbols, "symbols");
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return Token<TTag>.New( Enumerable.Range(0, AlphabetBuilder.Count).Except(TranslateOrDie(symbols)).ToArray() );
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}
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protected abstract IAlphabetBuilder<TSymbol> CreateAlphabet();
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protected RegularDFA<TSymbol, TTag> BuildDFA(Token<TTag> regexp) {
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var dfa = new RegularDFA<TSymbol, TTag>(AlphabetBuilder);
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var visitor = new RegularExpressionVisitor<TTag>();
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regexp.Accept( visitor );
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visitor.BuildDFA(dfa);
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if (dfa.IsFinalState(dfa.InitialState))
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throw new ApplicationException("The specified language contains empty token");
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return dfa.Optimize(CreateAlphabet());
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}
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}
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}
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