/*
* 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.number.Complex;
import cc.redberry.core.tensor.Product;
import cc.redberry.core.tensor.Sum;
import cc.redberry.core.tensor.Tensor;
import cc.redberry.core.tensor.TensorField;
import cc.redberry.core.tensor.functions.ScalarFunction;
import cc.redberry.core.tensor.iterator.TraverseGuide;
import cc.redberry.core.tensor.iterator.TraversePermission;
import cc.redberry.core.transformations.Transformation;
import cc.redberry.core.transformations.substitutions.SubstitutionIterator;
import cc.redberry.core.utils.TensorUtils;
import static cc.redberry.core.tensor.Tensors.reciprocal;
import static cc.redberry.core.utils.TensorUtils.isNegativeIntegerPower;
/**
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
*/
abstract class AbstractExpandTransformation implements Transformation {
public static TraverseGuide DefaultExpandTraverseGuide = new TraverseGuide() {
@Override
public TraversePermission getPermission(Tensor tensor, Tensor parent, int indexInParent) {
if (tensor instanceof ScalarFunction)
return TraversePermission.DontShow;
if (tensor instanceof TensorField)
return TraversePermission.DontShow;
if (isNegativeIntegerPower(tensor))
return TraversePermission.DontShow;
return TraversePermission.Enter;
}
};
protected final Transformation[] transformations;
protected final TraverseGuide traverseGuide;
protected AbstractExpandTransformation() {
this(new Transformation[0], DefaultExpandTraverseGuide);
}
protected AbstractExpandTransformation(Transformation[] transformations) {
this(transformations, DefaultExpandTraverseGuide);
}
/**
* 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 transformations to be applied after each step of expand
* @param traverseGuide traverse guide
*/
protected AbstractExpandTransformation(Transformation[] transformations, TraverseGuide traverseGuide) {
this.transformations = transformations;
this.traverseGuide = traverseGuide;
}
@Override
public Tensor transform(Tensor tensor) {
SubstitutionIterator iterator = new SubstitutionIterator(tensor, traverseGuide);
Tensor current;
while ((current = iterator.next()) != null) {
if (current instanceof Product)
iterator.unsafeSet(expandProduct((Product) current, transformations));
else if (ExpandUtils.isExpandablePower(current)) {
Sum sum = (Sum) current.get(0);
int exponent = ((Complex) current.get(1)).intValue();
if (exponent == -1)
continue;
boolean symbolic = TensorUtils.isSymbolic(sum),
reciprocal = exponent < 0;
exponent = Math.abs(exponent);
Tensor temp;
if (symbolic)
temp = ExpandUtils.expandSymbolicPower(sum, exponent, transformations);
else
temp = ExpandUtils.expandPower(sum, exponent, iterator.getForbidden(), transformations);
if (reciprocal)
temp = reciprocal(temp);
if (symbolic)
iterator.unsafeSet(temp);
else
iterator.set(temp);
}
}
return iterator.result();
}
protected abstract Tensor expandProduct(Product product, Transformation[] transformations);
}