/*
* 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.tensor;
import cc.redberry.core.number.Complex;
import cc.redberry.core.number.Exponentiation;
import cc.redberry.core.utils.TensorUtils;
/**
* {@link TensorFactory} for powers. It performs basic simplifications and reduces the
* resulting power to the standard form.
*
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
* @see Power
* @since 1.0
*/
public final class PowerFactory implements TensorFactory {
public static final PowerFactory FACTORY = new PowerFactory();
private PowerFactory() {
}
@Override
public Tensor create(Tensor... tensors) {
checkWithException(tensors);
return power(tensors[0], tensors[1]);
}
static Tensor power(Tensor argument, Tensor power) {
//TODO improve Complex^Complex
if (argument instanceof Complex && power instanceof Complex) {
Complex a = (Complex) argument;
Complex p = (Complex) power;
Complex result = Exponentiation.exponentiateIfPossible(a, p);
if (result != null)
return result;
}
if (TensorUtils.isOne(power))
return argument;
if (TensorUtils.isZero(power) || TensorUtils.isOne(argument))
return Complex.ONE;
if (TensorUtils.isZero(argument))
return Complex.ZERO;
if (argument instanceof Product) {
Tensor[] scalars = ((Product) argument).getAllScalars();
if (scalars.length > 1) {
TensorBuilder pb = argument.getBuilder();//creating product builder
for (Tensor t : scalars)
pb.put(Tensors.pow(t, power));//TODO refactor for performance
return pb.build();
}
}
if (argument instanceof Power)
return Tensors.pow(argument.get(0), Tensors.multiply(argument.get(1), power));
return new Power(argument, power);
}
private static void checkWithException(Tensor[] tensors) {
if (tensors.length != 2)
throw new IllegalArgumentException("Wrong number of arguments.");
if (!TensorUtils.isScalar(tensors))
throw new IllegalArgumentException("Non scalar power parametres.");
for (Tensor t : tensors)
if (t == null)
throw new NullPointerException();
}
}