回答編集履歴
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answer
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`std::valarray<double>` を sliceする方が万倍楽ちゃいますか?
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`std::valarray<double>` を sliceする方が万倍楽ちゃいますか?
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[追記]
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columnを返すのやってみた:
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```C++
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#include <iostream>
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#include <algorithm>
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template<typename T>
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class column {
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public:
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column(T* data, size_t cols) : data_(data), cols_(cols) {}
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T& operator[](size_t row) { return data_[cols_*row]; }
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private:
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T* data_;
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size_t cols_;
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};
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template<typename T>
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class matrix {
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public:
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matrix(size_t rows, size_t cols) : cols_(cols), rows_(rows) {
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data_ = new T[rows*cols];
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}
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~matrix() { delete[] data_; }
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void fill(const T& val) { std::fill_n(data_, rows_*cols_, val); }
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column<T> operator()(size_t col) { return column<T>(data_+col, cols_); }
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T* operator[](size_t row) { return data_+cols_*row; }
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private:
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T* data_;
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size_t cols_;
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size_t rows_;
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};
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// おためし
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int main() {
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using namespace std;
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matrix<double> mtx(2,3);
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mtx.fill(0.0);
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column<double> clm = mtx(1);
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clm[0] = 1.23;
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clm[1] = 2.34;
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for ( size_t r = 0; r < 2; ++r ) {
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for ( size_t c = 0; c < 3; ++c ) {
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cout << mtx[r][c] << ' ';
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}
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cout << endl;
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}
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}
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```
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