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Redberry is an open source computer algebra system designed for tensor manipulation. It implements basic computer algebra system routines as well as complex tools for real computations in physics. This is Redberry core, which contains the implementation of the basic computer algebra routines and general-purpose transformations.

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/*
 * Redberry: symbolic tensor computations.
 *
 * Copyright (c) 2010-2014:
 *   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;

import cc.redberry.core.indices.Indices;
import cc.redberry.core.indices.IndicesUtils;
import cc.redberry.core.number.Complex;
import cc.redberry.core.tensor.SimpleTensor;
import cc.redberry.core.tensor.Tensor;
import cc.redberry.core.tensor.TensorField;
import cc.redberry.core.tensor.functions.ScalarFunction;
import gnu.trove.set.TIntSet;
import gnu.trove.set.hash.TIntHashSet;

import java.util.HashSet;
import java.util.Set;

/**
 * Utility methods to work with AST.
 *
 * @author Dmitry Bolotin
 * @author Stanislav Poslavsky
 * @since 1.0
 */
public class ParseUtils {

    private ParseUtils() {
    }

    public static boolean checkBracketsConsistence(String expression) {
        char[] expr = expression.toCharArray();
        int[] levels = new int[3];
        for (char c : expr) {
            if (levels[0] < 0 || levels[1] < 0 || levels[2] < 0) return false;
            switch (c) {
                case '(':
                    ++levels[0];
                    break;
                case ')':
                    --levels[0];
                    break;
                case '[':
                    ++levels[1];
                    break;
                case ']':
                    --levels[1];
                    break;
                case '{':
                    ++levels[2];
                    break;
                case '}':
                    --levels[2];
                    break;
                default:
            }
        }
        return levels[0] == 0 && levels[1] == 0 && levels[2] == 0;
    }

    public static ParseToken tensor2AST(Tensor tensor) {
        if (tensor instanceof TensorField) {
            TensorField tf = (TensorField) tensor;
            ParseToken[] content = new ParseToken[tf.size()];
            int i = 0;
            for (Tensor t : tf)
                content[i++] = tensor2AST(t);
            return new ParseTokenTensorField(tf.getIndices(), tf.getStringName(), content, tf.getArgIndices());
        }
        if (tensor instanceof SimpleTensor) {
            SimpleTensor st = (SimpleTensor) tensor;
            return new ParseTokenSimpleTensor(st.getIndices(), st.getStringName());
        }
        if (tensor instanceof Complex)
            return new ParseTokenNumber((Complex) tensor);

        ParseToken[] content = new ParseToken[tensor.size()];
        int i = 0;
        for (Tensor t : tensor)
            content[i++] = tensor2AST(t);

        if (tensor instanceof ScalarFunction)
            return new ParseTokenScalarFunction(tensor.getClass().getSimpleName(), content);
        return new ParseToken(TokenType.valueOf(tensor.getClass().getSimpleName()), content);
    }

    public static Set getAllIndices(ParseToken node) {
        Set s = new HashSet<>();
        getAllIndices1(node, s);
        return s;
    }

    private static void getAllIndices1(ParseToken node, Set set) {
        if (node instanceof ParseTokenSimpleTensor) {
            Indices indices = node.getIndices();
            for (int i = indices.size() - 1; i >= 0; --i)
                set.add(IndicesUtils.getNameWithType(indices.get(i)));
        } else
            for (ParseToken pn : node.content)
                if (!(pn instanceof ParseTokenScalarFunction))
                    getAllIndices1(pn, set);
    }

    public static TIntSet getAllIndicesT(ParseToken node) {
        TIntSet set = new TIntHashSet();
        getAllIndicesT1(node, set);
        return set;
    }

    private static void getAllIndicesT1(ParseToken node, TIntSet set) {
        if (node instanceof ParseTokenSimpleTensor) {
            Indices indices = node.getIndices();
            for (int i = indices.size() - 1; i >= 0; --i)
                set.add(IndicesUtils.getNameWithType(indices.get(i)));
        } else
            for (ParseToken pn : node.content)
                if (!(pn instanceof ParseTokenScalarFunction))
                    getAllIndicesT1(pn, set);
    }
}