/*
* 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;
import cc.redberry.core.tensor.Tensor;
import cc.redberry.core.tensor.TensorBuilder;
/**
* Transformation of tensor.
*
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
*/
public interface Transformation {
/**
* Singleton instance for identity transformation.
*/
public static final Transformation INDENTITY = new Transformation() {
@Override
public Tensor transform(Tensor t) {
return t;
}
};
public static final class Util {
private Util() {
}
public static Tensor applySequentially(Tensor tensor, final Transformation... transformations) {
for (Transformation tr : transformations)
tensor = tr.transform(tensor);
return tensor;
}
/**
* Applies transformation to all first descendants (but not to the tensor itself)
*
* @param tensor
* @param transformation
* @return
*/
public static Tensor applyToEachChild(Tensor tensor, final Transformation transformation) {
TensorBuilder builder = null;
Tensor c, oc;
for (int i = 0, size = tensor.size(); i < size; ++i) {
c = transformation.transform(oc = tensor.get(i));
if (builder != null || c != oc) {
if (builder == null) {
builder = tensor.getBuilder();
for (int j = 0; j < i; ++j)
builder.put(tensor.get(j));
}
builder.put(c);
}
}
if (builder == null)
return tensor;
return builder.build();
}
}
/**
* Transforms specified tensor and returns the result.
*
* @param t tensor
* @return transformed tensor
*/
Tensor transform(Tensor t);
}