jtabwbx.modal.parser.ModalFormulaParser.java Source code

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Here is the source code for jtabwbx.modal.parser.ModalFormulaParser.java

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/*******************************************************************************
 * Copyright (C) 2013, 2016 Mauro Ferrari This program 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. This program 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 this program; if not, see
 * <http://www.gnu.org/licenses/>.
 ******************************************************************************/
package jtabwbx.modal.parser;

import org.antlr.v4.runtime.RecognitionException;
import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.BaseErrorListener;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.Recognizer;
import org.antlr.v4.runtime.atn.PredictionMode;
import org.antlr.v4.runtime.tree.ParseTree;

/**
 * A parser for propositional formulas. Formulas must be defined as follows:
 * <ul>
 * <li><b>Propositional variables</b>.
 * <code>["_","a"-"z","A"-"Z"] | (["_","a"-"z","A"-"Z"] | ["0"-"9"])* </code></li>
 * <li><b>Logical constants</b>. Listed in order of precedence (from highest to
 * lowest):
 * <ul>
 * <li><code>true</code>, <code>false</code></li>
 * <li><code>~</code> (not): prefix, unary</li>
 * <li><code>&amp;</code> (and): infix, binary</li>
 * <li><code>|</code> (or): infix, binary</li>
 * <li><code>&lt;=&gt;</code> (iff): infix, binary</li>
 * <li><code>box</code>: prefix, unary</li>
 * <li><code>dia</code> (diamond): prefix, unary</li>
 * </ul>
 * </li>
 * </ul>
 * 
 * @author Mauro Ferrari
 */
public class ModalFormulaParser {

    private final String name = "Propositional_formula_parser";

    /**
     * Constructs a parser.
     */
    public ModalFormulaParser() {
    }

    /**
     * Parses the string given as argument and returns the corresponding
     * {@link ParseTree}.
     * 
     * @param str the string describing the formula.
     * @return the parse tree.
     * @throws ModalFormulaParseException if an error occurs during parsing.
     */
    public ParseTree parse(String str) throws ModalFormulaParseException {
        try {
            ModalFormulaLexerSignalingErrors lexer = new ModalFormulaLexerSignalingErrors(
                    new ANTLRInputStream(str));
            lexer.removeErrorListeners();
            lexer.addErrorListener(new ErrorListener());
            CommonTokenStream tokens = new CommonTokenStream(lexer);
            ModalWffParser parser = new ModalWffParser(tokens);
            parser.removeErrorListeners();
            parser.addErrorListener(new ErrorListener());
            parser.getInterpreter().setPredictionMode(PredictionMode.SLL);
            ParseTree tree = parser.modalFormula();
            return tree;
        } catch (ParserError e) {
            throw new ModalFormulaParseException(e.getMessage());
        }
    }

    /**
     * Returns the parser name.
     * 
     * @return the parser name.
     */
    public String getName() {
        return name;
    }

    /**
     * Returns a description of the parser.
     * 
     * @return the string describing the parser.
     */
    public String getDescription() {
        return "Formula formula parser\n"
                + "Propositional variables: ['_','a'-'z','A'-'Z'] | (['_','a'-'z','A'-'Z'] | ['0'-'9'])*\n"
                + "Logical constants: true, false, & (and), | (or), ~ (not), -> (implies), <=> (equivalence)";
    }

    static void main(String[] args) {
        ModalFormulaParser parser = new ModalFormulaParser();
        try {
            ParseTree pt = parser.parse(args[0]);
            System.out.println(pt.toString());
        } catch (ModalFormulaParseException e) {
            System.out.println(e.toString());
        }
    }

    static class ErrorListener extends BaseErrorListener {

        @Override
        public void syntaxError(Recognizer<?, ?> recognizer, Object offendingSymbol, int line,
                int charPositionInLine, String msg, RecognitionException e) {
            throw new ParserError("line " + line + ":" + charPositionInLine + " - " + msg);
        }

    }

}