`bit::matrix` — Element Access

We have methods to access the rows, the columns, and the individual elements/bits in a bit-matrix.

constexpr bool
1operator()(std::size_t i, std::size_t j);

constexpr bool
2test(std::size_t i, std::size_t j) const;

constexpr bit::vector::reference
3operator()(std::size_t i, std::size_t j);

constexpr const bit::vector&
4row(std::size_t i) const;

constexpr bit::vector&
row(std::size_t i);

constexpr const bit::vector&
5operator[](std::size_t i) const;

constexpr bit::vector&
operator[](std::size_t i);

constexpr bit::vector
6col(std::size_t j) const;

1: Accesses the element at (i, j).
2: Another way to access element (i, j).
3: Returns an object of type vector::reference that lets you write to slot (i, j).
4: Read-only & read-write access to the elements in row i of a bit-matrix.
5: Synonyms for the row(i) methods to allow for alternate C style indexing a la matrix[i][j].
6: Read-only access to the elements in column i of a bit-matrix.

In general, these methods do not check whether an index is in bounds, and if it isn’t, the behaviour is undefined (but bound to be wrong!) Set the BIT_VERIFY flag at compile time to check this condition — any violation will cause the program to abort with a helpful message.

Example

#include <bit/bit.h>
int main()
{
    std::size_t n = 4;
    auto mat = bit::matrix<>::random(n);
    std::cout << "bit::matrix:\n";
    std::cout << mat << '\n';
    std::cout << "By rows ...\n";
    for (std::size_t i = 0; i < n; ++i)
        std::cout << "Row " << i << ": " << mat[i] << '\n';
    std::cout << "By columns ...\n";
    for (std::size_t i = 0; i < n; ++i)
        std::cout << "Col " << i << ": " << mat.col(i) << '\n';
}

Output

bit::matrix:
│0 1 1 0│
│0 1 0 0│
│0 1 1 0│
│0 1 0 0│
By rows ...
Row 0: [0 1 1 0]
Row 1: [0 1 0 0]
Row 2: [0 1 1 0]
Row 3: [0 1 0 0]
By columns ...
Col 0: [0 0 0 0]
Col 1: [1 1 1 1]
Col 2: [1 0 1 0]

See Also