/*
* 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.transformations.expand;
import cc.redberry.core.tensor.Product;
import cc.redberry.core.tensor.Tensor;
import cc.redberry.core.tensor.Tensors;
import cc.redberry.core.tensor.iterator.TraverseGuide;
import cc.redberry.core.transformations.Transformation;
import cc.redberry.core.transformations.fractions.NumeratorDenominator;
/**
* Expands out products and powers that appear as numerators in expressions.
*
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
* @since 1.0
*/
public final class ExpandNumeratorTransformation extends AbstractExpandTransformation {
/**
* The default instance.
*/
public static final ExpandNumeratorTransformation EXPAND_NUMERATOR = new ExpandNumeratorTransformation();
private ExpandNumeratorTransformation() {
super();
}
/**
* Creates expand transformation with specified additional transformations to
* be applied after each step of expand.
*
* @param transformations transformations to be applied after each step of expand
*/
public ExpandNumeratorTransformation(Transformation[] transformations) {
super(transformations);
}
/**
* Creates expand transformation with specified additional transformations to
* be applied after each step of expand and leaves unexpanded parts of expression specified by
* {@code traverseGuide}.
*
* @param transformations transformations to be applied after each step of expand
* @param traverseGuide traverse guide
*/
public ExpandNumeratorTransformation(Transformation[] transformations, TraverseGuide traverseGuide) {
super(transformations, traverseGuide);
}
/**
* Expands out products and powers that appear as numerators of tensor.
*
* @param tensor tensor to be transformed
* @return result
*/
public static Tensor expandNumerator(Tensor tensor) {
return EXPAND_NUMERATOR.transform(tensor);
}
/**
* Expands out products and powers that appear as numerators of tensor and applies specified transformations
* after each step of expand.
*
* @param tensor tensor to be transformed
* @return result
*/
public static Tensor expandNumerator(Tensor tensor, Transformation... transformations) {
return new ExpandNumeratorTransformation(transformations).transform(tensor);
}
@Override
protected Tensor expandProduct(Product product, Transformation[] transformations) {
NumeratorDenominator numDen = NumeratorDenominator.getNumeratorAndDenominator(product, NumeratorDenominator.integerDenominatorIndicator);
Tensor numerator = numDen.numerator;
if (numerator instanceof Product)
numerator = ExpandUtils.expandProductOfSums((Product) numDen.numerator, transformations);
if (numDen.numerator == numerator)
return product;
return Tensors.multiply(numerator, Tensors.reciprocal(numDen.denominator));
}
}