mqn2mps: triplet.hh Source File

00001 /*
00002  *  Copyright 2007 Martin von Gagern
00003  *
00004  *
00005  *  This file is part of mqn2mps.
00006  *
00007  *  mqn2mps is free software; you can redistribute it and/or modify
00008  *  it under the terms of the GNU General Public License as published by
00009  *  the Free Software Foundation; either version 3 of the License, or
00010  *  (at your option) any later version.
00011  *
00012  *  mqn2mps is distributed in the hope that it will be useful,
00013  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  *  GNU General Public License for more details.
00016  *
00017  *  You should have received a copy of the GNU General Public License
00018  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
00019  */
00020 
00021 
00022 #ifndef TRIPLET_HH
00023 #define TRIPLET_HH
00024 
00025 /**
00026  * @file
00027  * Interface and implementation of class triplet.
00028  */
00029 
00030 /**
00031  * Verbose description of a matrix element.
00032  *
00033  * A triplet consists of row and column indices in a matrix together
00034  * with the value of the corresponding matrix cell. As the full
00035  * position information is part of the object, a triplet can describe
00036  * a matrix element all by itself, and an unordered collection of
00037  * triplets with unique addresses can describe all nonzero entries of
00038  * a matrix.
00039  *
00040  * @see make_triplet()
00041  */
00042 template<class T> class triplet {
00043 public:
00044 
00045   /**
00046    * The row index inside the matrix.
00047    */
00048   int row;
00049 
00050   /**
00051    * The column index inside the matrix.
00052    */
00053   int col;
00054 
00055   /**
00056    * The value of the matrix element at the specified position.
00057    */
00058   T val;
00059 
00060   /**
00061    * Default constructor.
00062    */
00063   triplet() : row(0), col(0), val(0) { }
00064 
00065   /**
00066    * Full constructor.
00067    *
00068    * @param r the row index.
00069    * @param c the column index.
00070    * @param v the value.
00071    */
00072   triplet(int r, int c, T v) : row(r), col(c), val(v) { }
00073 
00074   /**
00075    * Lexicographical comparison of triplets.
00076    * @param t the second triplet with which this one is to be
00077    *          compared.
00078    * @return whether this triplet is lexicographically less than
00079    *         @e t. 
00080    */
00081   bool operator<(const triplet& t) const {
00082     if (row != t.row) return row < t.row;
00083     if (col != t.col) return col < t.col;
00084     return val < t.val;
00085   }
00086 
00087 };
00088 
00089 /**
00090  * Templated generation of triplet objects.
00091  *
00092  * Using this method instead of the constructor triplet::triplet, the
00093  * type of the triplet to be created can be derived from the type of
00094  * the value argument. Therefore no template types have to be given,
00095  * which leads to shorter code. This is similar to std::make_pair().
00096  *
00097  * @param row the row index.
00098  * @param col the column index.
00099  * @param val the value.
00100  */
00101 template<class T> inline triplet<T> make_triplet(int row, int col, T val) {
00102   return triplet<T>(row, col, val);
00103 }
00104 
00105 #endif // ifndef TRIPLET_HH