cc.redberry.core.parser.ParserBrackets Maven / Gradle / Ivy

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/*
 * Redberry: symbolic tensor computations.
 *
 * Copyright (c) 2010-2013:
 *   Stanislav Poslavsky   
 *   Bolotin Dmitriy       
 *
 * This file is part of Redberry.
 *
 * Redberry 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.
 *
 * Redberry 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 Redberry. If not, see .
 */
package cc.redberry.core.parser;

/**
 * Parses expressions of form in brackets.
 *
 * @author Dmitry Bolotin
 * @author Stanislav Poslavsky
 * @since 1.0
 */
public class ParserBrackets implements TokenParser {
    public static final ParserBrackets INSTANCE = new ParserBrackets();

    private ParserBrackets() {
    }

    private final static int parserID = Integer.MAX_VALUE;

    @Override
    public ParseToken parseToken(String expression, Parser parser) {
        if (expression.charAt(0) == '(' && expression.charAt(expression.length() - 1) == ')') {
            char[] expressionChars = expression.toCharArray();
            int level = 0;
            for (char c : expressionChars) {
                if (c == '(')
                    level++;
                if (level < 1)
                    return null;
                if (c == ')')
                    level--;
            }
            if (level != 0)
                throw new BracketsError();
            return parser.parse(expression.substring(1, expression.length() - 1));
        } else
            return null;
    }

    @Override
    public int priority() {
        return parserID;
    }
}