/* The following code example is taken from the book * "The C++ Standard Library - A Tutorial and Reference" * by Nicolai M. Josuttis, Addison-Wesley, 1999 * * (C) Copyright Nicolai M. Josuttis 1999. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */ #include <iostream> #include <valarray> using namespace std; // print three-dimensional valarray line-by-line template<class T> void printValarray3D (const valarray<T>& va, int dim1, int dim2) { for (int i=0; i<va.size()/(dim1*dim2); ++i) { for (int j=0; j<dim2; ++j) { for (int k=0; k<dim1; ++k) { cout << va[i*dim1*dim2+j*dim1+k] << ' '; } cout << '\n'; } cout << '\n'; } cout << endl; } int main() { /* valarray with 24 elements * - two groups * - four rows * - three columns */ valarray<double> va(24); // fill valarray with values for (int i=0; i<24; i++) { va[i] = i; } // print valarray printValarray3D (va, 3, 4); // we need two two-dimensional subsets of three times 3 values // in two 12-element arrays size_t lengthvalues[] = { 2, 3 }; size_t stridevalues[] = { 12, 3 }; valarray<size_t> length(lengthvalues,2); valarray<size_t> stride(stridevalues,2); // assign the second column of the first three rows // to the first column of the first three rows va[gslice(0,length,stride)] = valarray<double>(va[gslice(1,length,stride)]); // add and assign the third of the first three rows // to the first of the first three rows va[gslice(0,length,stride)] += valarray<double>(va[gslice(2,length,stride)]); // print valarray printValarray3D (va, 3, 4); } /* 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 3 1 2 9 4 5 15 7 8 9 10 11 27 13 14 33 16 17 39 19 20 21 22 23 */
Print three-dimensional valarray line-by-line
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