cc.redberry.transformation.ExpandBrackets Maven / Gradle / Ivy

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/*
 * Redberry: symbolic tensor computations.
 *
 * Copyright (c) 2010-2012:
 *   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.transformation;

import java.util.ArrayList;
import cc.redberry.core.tensor.Product;
import cc.redberry.core.tensor.Sum;
import cc.redberry.core.tensor.Tensor;
import cc.redberry.core.tensor.TensorIterator;
import cc.redberry.core.utils.Indicator;

/**
 *
 * @author Dmitry Bolotin
 * @author Stanislav Poslavsky
 */
public final class ExpandBrackets implements Transformation {
    public static final ExpandBrackets EXPAND_ALL = new ExpandBrackets(Indicator.FALSE_INDICATOR);
    public static final ExpandBrackets EXPAND_EXCEPT_SYMBOLS = new ExpandBrackets(Indicator.SYMBOL_INDICATOR);
    private final Indicator except;

    public ExpandBrackets(Indicator except) {
        this.except = except;
    }

    @Override
    public Tensor transform(Tensor tensor) {
        if (!(tensor instanceof Product))
            return tensor;
        //was required by cc.redberry-physics
        if (except.is(tensor))
            return tensor;
        TensorIterator productIterator = tensor.iterator();
        ArrayList products = new ArrayList<>();
        ArrayList newProducts;
        products.add(new Product());
        Tensor t = null;
        int oldSize, i;
        Sum sum;
        boolean sumsExists = false;
        while (productIterator.hasNext()) {
            t = productIterator.next();
            if (t instanceof Sum && !except.is(t)) {
                sumsExists = true;
                sum = (Sum) t;
                oldSize = products.size();
                newProducts = new ArrayList<>(oldSize * sum.size());
                i = 0;
                for (Tensor sumElement : sum)
                    for (int j = 0; j < oldSize; ++j) {
                        newProducts.add((Product) products.get(j).clone());
                        newProducts.get(i++).add(sumElement.clone());
                    }
                products = newProducts;
            } else
                for (Product product : products)
                    product.add(t.clone());
        }
        if (sumsExists)
            return new Sum(products);
//            return new Sum(products).clone();
        return tensor;
    }
}