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C++ lambda powered matrix
#pragma once
// (c) 2019-2020 by dbj@dbj.org
// License: CC BY SA 4.0
#include <iomanip> // setw
#include <sstream>
#include <array>
#include <cassert>
#include <string>
#include <vector>
namespace dbj::mtx {
enum class version { major = 5, minor = 0, patch = 0 };
template< typename T, size_t len_ >
inline constexpr auto arr_stack() { return std::array<T, len_>{ {}}; }
template< typename T, size_t len_ >
inline std::vector<T> arr_heap() { return std::vector<T>(len_); }
template< typename T, size_t rows, size_t cols, typename F >
inline constexpr auto mx(F source_)
{
return[arry = source_()]
(size_t row_, size_t col_) /*constexpr*/ mutable->T&
{
assert(row_ <= rows);
assert(col_ <= cols);
return arry[row_ * rows + col_];
};
} // mx
#undef dbj_mx_make
#undef dbj_mx_make_heap
#undef dbj_mx_make_stack
#define dbj_mx_make(T, R, C, K) dbj::mtx::mx<T, R, C>(dbj::mtx::K<T, R * C>)
#define dbj_mx_make_heap(T,R,C) dbj_mx_make(T, R, C, arr_heap)
#define dbj_mx_make_stack(T,R,C) dbj_mx_make(T, R, C, arr_stack)
///
/// Testing
///
#ifdef DBJ_MTX_TESTING
inline auto changer = []( auto matrix_, size_t row_, size_t col_, auto value_) {
matrix_(row_, col_) = value_;
return matrix_;
};
// print to buffer
inline auto
printer = [](auto matrix_, size_t width_, size_t height_)
-> std::string {
using namespace std;
std::ostringstream rez_;
for (size_t row_ = 0; row_ < width_; row_++) {
rez_ << endl << "{";
for (size_t col_ = 0; col_ < height_; col_++) {
rez_ << setw(3) << matrix_(row_, col_) << " ";
}
rez_ << "}";
}
rez_ << endl;
return rez_.str();
};
///
/// log callback signature:
/// void (*)( std::string_view )
///
template<typename log_callback >
inline void test_dbj_matrix_creation( log_callback log )
{
using namespace dbj::mtx;
using namespace std;
constexpr size_t width_ = 3; // 0,1,2
constexpr size_t height_ = 3; // 0,1,2
constexpr size_t last_col_ = width_ - 1; // 0,1,2
constexpr size_t last_row_ = height_ - 1; // 0,1,2
// test move in, move out and the rest
auto reporter = [&](auto matrix_, const char* prompt_) {
string report = prompt_ +
printer(changer(matrix_, last_col_, last_row_, 42), width_, height_);
log(report);
return matrix_;
};
auto mxs = reporter(dbj_mx_make_stack(int, width_, height_),
"\n matrix_on_stack \n" );
auto mxh = reporter(dbj_mx_make_heap(int, width_, height_),
"\n matrix_on_heap \n");
}
#endif // DBJ_MTX_TESTING
} // dbj::mtx
@DBJDBJ

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DBJDBJ commented Mar 14, 2020

5.0.0 is "dramatic" change. Had to use std::vector for heap based matrix after all. std::unique_ptr disables ability to copy and std::shared_ptr is abomination.

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