/*
* 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.indexmapping;
import cc.redberry.core.number.Complex;
import cc.redberry.core.number.NumberUtils;
import cc.redberry.core.tensor.Tensor;
/**
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
* @since 1.0
*/
class ProviderPower implements IndexMappingProviderFactory {
static final ProviderPower INSTANCE = new ProviderPower();
private ProviderPower() {
}
@Override
public IndexMappingProvider create(IndexMappingProvider opu, Tensor from, Tensor to) {
IndexMappingBuffer exponentMapping = IndexMappings.getFirst(from.get(1), to.get(1)); //todo try get first positive mapping
if (exponentMapping == null || exponentMapping.getSign())
return IndexMappingProvider.Util.EMPTY_PROVIDER;
//todo two signs are possible
IndexMappingBuffer baseMapping = IndexMappings.getFirst(from.get(0), to.get(0));
if (baseMapping == null)
return IndexMappingProvider.Util.EMPTY_PROVIDER;
if (baseMapping.getSign() == false)
return new DummyIndexMappingProvider(opu);
if (!(from.get(1) instanceof Complex))
return IndexMappingProvider.Util.EMPTY_PROVIDER;
assert to.get(1) instanceof Complex;
Complex exponent = (Complex) from.get(1);
if (NumberUtils.isIntegerEven(exponent))
return new DummyIndexMappingProvider(opu);
if (NumberUtils.isIntegerOdd(exponent))
return new MinusIndexMappingProvider(opu);
return IndexMappingProvider.Util.EMPTY_PROVIDER;
}
}