C++ Cookbook

11.15. Implementing a Constant-Sized Matrix

Problem

You want an efficient matrix implementation where the dimensions (i.e., number of rows and columns) are constants known at compile time.

Solution

When the dimensions of a matrix are known at compile time, the compiler can more easily optimize an implementation that accepts the row and columns as template parameters as shown in Example 11-30.

Example 11-30. kmatrix.hpp

#ifndef KMATRIX_HPP #define KMATRIX_HPP #include "kvector.hpp" #include "kstride_iter.hpp" template<class Value_T, int Rows_N, int Cols_N> class kmatrix { public: // public typedefs typedef Value_T value_type; typedef kmatrix self; typedef Value_T* iterator; typedef const Value_T* const_iterator; typedef kstride_iter<Value_T*, 1> row_type; typedef kstride_iter<Value_T*, Cols_N> col_type; typedef kstride_iter<const Value_T*, 1> const_row_type; typedef kstride_iter<const Value_T*, Cols_N> const_col_type; // public constants static const int nRows = Rows_N; static const int nCols = Cols_N; // constructors kmatrix() { m = Value_T(); } kmatrix(const self& x) { m = x.m; } explicit kmatrix(Value_T& x) { m = x.m; } // public functions static int rows() { return Rows_N; } static int cols() { return Cols_N; } row_type row(int n) { return row_type(begin() + (n * Cols_N)); } col_type col(int n) { return col_type(begin() + n); } const_row_type row(int n) const { return const_row_type(begin() + (n * Cols_N)); } const_col_type col(int n) const { return const_col_type(begin() + n); ...