/*
 *            Copyright 2009-2018 The VOTCA Development Team
 *                       (http://www.votca.org)
 *
 *      Licensed under the Apache License, Version 2.0 (the "License")
 *
 * You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *              http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#ifndef _VOTCA_XTP_VC2INDEX_H
#define _VOTCA_XTP_VC2INDEX_H


namespace votca {
namespace xtp {
/**
* \brief This class transforms a pair of indices v,c into a compound index I, via I=ctotal*v+c
* the fast dimension is c. If you have a choice iterate over c and v not over I. 
*
*
*/
class vc2index {

public:

    vc2index(int vmin, int cmin, int ctotal):_vmin(vmin),_cmin(cmin),_ctotal(ctotal){};

    inline int I(int v,int c)const{return _ctotal*(v-_vmin)+c-_cmin;}

    inline int v(int index)const{return index/_ctotal+_vmin;}

    inline int c(int index)const{return index%_ctotal+_cmin;}


private:


int _vmin;
int _cmin;
int _ctotal;
    
};
}
}

#endif /* _VOTCA_XTP_VC2INDEX_H */