/*
* 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.utils;
import cc.redberry.core.context.CC;
import cc.redberry.core.indices.IndexType;
import cc.redberry.core.indices.SimpleIndices;
import cc.redberry.core.tensor.SimpleTensor;
import static cc.redberry.core.indices.IndicesUtils.getState;
/**
* Utils fot matrices.
*
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
* @since 1.1.7
*/
public final class MatrixUtils {
private MatrixUtils() {
}
/**
* Returns whether specified tensor is matrix of specified type and with specified signature.
*
* @param tensor simple tensor
* @param type type of matrix
* @param upper number of upper matrix indices
* @param lower number of lower matrix indices
* @return true if specified tensor is matrix of specified type and with specified signature and false in other case
*/
public static boolean isGeneralizedMatrix(SimpleTensor tensor, IndexType type, int upper, int lower) {
if (CC.isMetric(type))
throw new IllegalArgumentException("Matrices can not be of metric type.");
SimpleIndices indices = tensor.getIndices().getOfType(type);
int i = 0;
for (; i < upper; ++i)
if (!getState(indices.get(i)))
return false;
upper += lower;
for (; i < upper; ++i)
if (getState(indices.get(i)))
return false;
return true;
}
/**
* Returns whether specified tensor is matrix of specified type.
*
* @param tensor simple tensor
* @param type type of matrix
* @return true if specified tensor is matrix of specified type and false in other case
*/
public static boolean isMatrix(SimpleTensor tensor, IndexType type) {
return isGeneralizedMatrix(tensor, type, 1, 1);
}
/**
* Returns whether specified tensor is vector of specified type.
*
* @param tensor simple tensor
* @param type type of matrix
* @return true if specified tensor is vector of specified type and false in other case
*/
public static boolean isVector(SimpleTensor tensor, IndexType type) {
return isGeneralizedMatrix(tensor, type, 1, 0);
}
/**
* Returns whether specified tensor is covector of specified type.
*
* @param tensor simple tensor
* @param type type of matrix
* @return true if specified tensor is covector of specified type and false in other case
*/
public static boolean isCovector(SimpleTensor tensor, IndexType type) {
return isGeneralizedMatrix(tensor, type, 0, 1);
}
}