56 lines
1.6 KiB
C++
56 lines
1.6 KiB
C++
// vslice.cpp -- using valarray slices
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#include <iostream>
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#include <valarray>
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#include <cstdlib>
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const int SIZE = 12;
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typedef std::valarray<int> vint; // simplify declarations
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void show(const vint & v, int cols);
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int main()
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{
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using std::slice; // from <valarray>
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using std::cout;
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vint valint(SIZE); // think of as 4 rows of 3
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int i;
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for (i = 0; i < SIZE; ++i)
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valint[i] = std::rand() % 10;
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cout << "Original array:\n";
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show(valint, 3); // show in 3 columns
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vint vcol(valint[slice(1,4,3)]); // extract 2nd column
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cout << "Second column:\n";
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show(vcol, 1); // show in 1 column
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vint vrow(valint[slice(3,3,1)]); // extract 2nd row
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cout << "Second row:\n";
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show(vrow, 3);
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valint[slice(2,4,3)] = 10; // assign to 2nd column
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cout << "Set last column to 10:\n";
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show(valint, 3);
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cout << "Set first column to sum of next two:\n";
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// + not defined for slices, so convert to valarray<int>
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valint[slice(0,4,3)] = vint(valint[slice(1,4,3)])
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+ vint(valint[slice(2,4,3)]);
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show(valint, 3);
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// std::cin.get();
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return 0;
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}
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void show(const vint & v, int cols)
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{
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using std::cout;
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using std::endl;
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int lim = v.size();
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for (int i = 0; i < lim; ++i)
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{
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cout.width(3);
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cout << v[i];
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if (i % cols == cols - 1)
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cout << endl;
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else
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cout << ' ';
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}
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if (lim % cols != 0)
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cout << endl;
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}
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