`GF2::Matrix` — Extract a Sub-Matrix

Extracts a sub-matrix as a stand-alone, distinct copy of elements from this bit-matrix.

constexpr Matrix sub(std::size_t i0, std::size_t j0, std::size_t r, std::size_t c) const;   (1)
constexpr Matrix sub(std::size_t r, std::size_t c) const;                               (2)
constexpr Matrix sub(std::size_t n) const const;                                      (3)

1	Returns an `r x c` bit-matrix that is a copy from this bit-matrix starting at `(i0, j0)`
2	Returns an `r x c` bit-matrix that is a copy from this bit-matrix starting at `(0, 0)`
3	Returns an `n x n` square bit-matrix that is a copy from this bit-matrix starting at `(0, 0)`

(i0, j0) has to be a valid index pair and the requested dimensions have to fit as a valid sub-matrix. As usual these requirements are only checked if the GF2_DEBUG flag is set at compile time—in which case violations will cause the program to abort with a helpful message.

Example

#include <GF2/GF2.h>
int main()
{
    auto m = GF2::Matrix<>::random(8);                                  (1)
    std::cout << "m:                \n" << m                << "\n";
    std::cout << "m.sub(4):         \n" << m.sub(4)         << "\n";    (2)
    std::cout << "m.sub(2,4):       \n" << m.sub(2,4)       << "\n";    (3)
    std::cout << "m.sub(5,5,3,3):   \n" << m.sub(5,5,3,3)   << "\n";    (4)
}

1	Constructs an 8 x 8 bit-matrix a random fill.
2	Extract the 4 x 4 elements starting at index (0, 0).
3	Extract the 2 x 4 elements starting at index (0, 0).
4	Extract the 3 x 3 elements starting at index (5, 5).

Output

m:
00001110
10100001
10100111
01101100
01000100
10001101
01011011
00000000
m.sub(4):
0000
1010
1010
0110
m.sub(2,4):
0000
1010
m.sub(5,5,3,3):
101
011
000

GF2::Matrix — Extract a Sub-Matrix

`GF2::Matrix` — Extract a Sub-Matrix