/*
* Redberry: symbolic tensor computations.
*
* Copyright (c) 2010-2013:
* Stanislav Poslavsky <stvlpos@mail.ru>
* Bolotin Dmitriy <bolotin.dmitriy@gmail.com>
*
* 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 <http://www.gnu.org/licenses/>.
*/
package cc.redberry.core.parser;
import cc.redberry.core.context.CC;
import cc.redberry.core.indices.IndicesFactory;
import cc.redberry.core.indices.SimpleIndices;
import cc.redberry.core.utils.IntArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Parser for indices of tensors.
*
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
* @since 1.0
*/
public final class ParserIndices {
/**
* Parses string expression an returns indices.
*
* @param expression string representation of indices
* @return integer indices
* @throws IllegalArgumentException if string does not represent correct indices object.
*/
public static SimpleIndices parseSimple(String expression) {
return IndicesFactory.createSimple(null, parse(expression));
}
/**
* Parses string expression an return integer array of indices.
*
* @param expression string representation of indices
* @return integer array of indices
* @throws IllegalArgumentException if string does not represent correct indices object.
*/
public static int[] parse(String expression) {
if (expression.isEmpty())
return new int[0];
IntArrayList indices = new IntArrayList();
int level = 0;
int state = 0;
final char[] expressionChars = expression.toCharArray();
char c;
int beginIndex = 0, endIndex = 0;
for (; endIndex < expressionChars.length; ++endIndex) {
c = expressionChars[endIndex];
if (c == '{')
++level;
else if (c == '}')
--level;
else if (c == '_' && level == 0) {
if (endIndex != 0)
parse(expression.substring(beginIndex + 1, endIndex), indices, state);
state = 0;
beginIndex = endIndex;
} else if (c == '^') {
if (level != 0)
throw new BracketsError();
if (endIndex != 0)
parse(expression.substring(beginIndex + 1, endIndex), indices, state);
state = 0x80000000;
beginIndex = endIndex;
}
}
if (level != 0)
throw new BracketsError();
if (beginIndex != endIndex)
parse(expression.substring(beginIndex + 1, endIndex), indices, state);
return indices.toArray();
}
/**
* A bit of regex
*/
public static final Pattern pattern = Pattern.compile("((?>(?>[a-zA-Z])|(?>\\\\[a-zA-Z]*))(?>_(?>(?>[0-9])|(?>[\\{][0-9\\s]*[\\}])))?[']*)");
static void parse(String expression, IntArrayList indices, int state) {
Matcher matcher = pattern.matcher(expression);
String singleIndex;
while (matcher.find()) {
singleIndex = matcher.group();
indices.add(CC.getIndexConverterManager().getCode(singleIndex) | state);
}
String remainder = matcher.replaceAll("");
remainder = remainder.replaceAll("[\\{\\}\\s]*", "");
if (remainder.length() != 0)
throw new ParserException();
}
}