Created
May 5, 2016 09:19
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#include <iostream> | |
#include <cstdlib> | |
#include <algorithm> | |
// dd.hpp | |
template <typename Derived> | |
struct DD_traits; | |
template <typename T> | |
class DD | |
{ | |
private: | |
using T_ret_type = typename DD_traits<T>::ret_type; | |
protected: | |
typename DD_traits<T>::ret_type **body_; | |
size_t size_x, size_y; | |
explicit DD(size_t x, size_t y) { | |
// if we got exception here, so there were no changes | |
body_ = new T_ret_type * [x]; | |
// if all is ok, it should be filled with nullptrs. just in case. | |
std::fill_n(body_, x, nullptr); | |
try { | |
for (size_t i = 0; i < x; ++i) | |
body_[i] = new T_ret_type [y] (); | |
} catch (...) { | |
for (size_t i = 0; i < x; ++i) | |
// it is safe to delete it, due to nulls. | |
delete [] body_[i]; | |
throw; | |
} | |
size_x = x, size_y = y; | |
} | |
~DD() { | |
for (int i = 0; i < size_x; ++i) | |
delete [] body_[i]; | |
delete [] body_; | |
} | |
public: | |
class RowLine { | |
T_ret_type *row_; | |
public: | |
RowLine (T_ret_type *row) : row_(row) {} | |
T_ret_type & operator[] (size_t j) { | |
return row_[j]; | |
} | |
}; | |
friend class ::DD<T>::RowLine; | |
RowLine operator[] (size_t i) { | |
return RowLine(body_[i]); | |
} | |
}; | |
// matrix.h | |
class Matrix; | |
template <> | |
struct DD_traits<Matrix> | |
{ | |
using ret_type = int; | |
}; | |
class Matrix : public DD<Matrix> | |
{ | |
public: | |
explicit Matrix (size_t x, size_t y) : DD<Matrix>(x, y) {} | |
}; | |
// main.cpp | |
int main () | |
{ | |
Matrix m(5, 5); | |
m[1][3] = 5; | |
std::cout << m[1][3]; | |
return 0; | |
} | |
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