/*
* Redberry: symbolic tensor computations.
*
* Copyright (c) 2010-2014:
* 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.powerexpand;
import cc.redberry.core.tensor.SimpleTensor;
import cc.redberry.core.tensor.Tensor;
import cc.redberry.core.tensor.Tensors;
import cc.redberry.core.transformations.Transformation;
import cc.redberry.core.transformations.substitutions.SubstitutionIterator;
import cc.redberry.core.utils.Indicator;
import static cc.redberry.core.transformations.powerexpand.PowerExpandUtils.*;
/**
* Expands all powers of products and powers with respect to specified variables and unwraps powers of
* indexed arguments into products (e.g. (A_m*A^m)**2 -> A_m*A^m*A_a*A^a).
*
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
* @since 1.1.5
*/
public final class PowerExpandUnwrapTransformation implements Transformation {
public static final PowerExpandUnwrapTransformation POWER_EXPAND_UNWRAP_TRANSFORMATION =
new PowerExpandUnwrapTransformation();
private final Indicator<Tensor> toExpandIndicator;
private PowerExpandUnwrapTransformation() {
this(Indicator.TRUE_INDICATOR);
}
/**
* Creates transformation that expands all powers of products and powers and
* unwraps powers of indexed arguments into products (e.g. (A_m*A^m)**2 -> A_m*A^m*A_a*A^a).
*
* @param toExpandIndicator applies only to powers that match this indicator
*/
public PowerExpandUnwrapTransformation(final Indicator<Tensor> toExpandIndicator) {
this.toExpandIndicator = toExpandIndicator;
}
/**
* Creates transformation that expands all powers of products and powers with respect to specified variables and
* unwraps powers of indexed arguments into products (e.g. (A_m*A^m)**2 -> A_m*A^m*A_a*A^a).
*
* @param vars patterns
*/
public PowerExpandUnwrapTransformation(final SimpleTensor[] vars) {
this(Indicator.Utils.iterativeIndicator(varsToIndicator(vars)));
}
@Override
public Tensor transform(Tensor t) {
SubstitutionIterator iterator = new SubstitutionIterator(t);
Tensor c;
while ((c = iterator.next()) != null)
if (powerExpandApplicable(c, toExpandIndicator))
iterator.set(Tensors.multiply(powerExpandIntoChainToArray1(c, iterator.getForbidden(), toExpandIndicator)));
return iterator.result();
}
}