`bit::vector` — Extract a Sub-Vector

We have methods to extract a sub-vector as a stand-alone, distinct copy of elements from this bit-vector.

1constexpr bit::vector sub(std::size_t begin, std::size_t len) const;
2constexpr bit::vector sub(int len) const;

1: Returns a bit-vector of size len, a copy of the elements starting at begin.
2: Returns a copy of the first len elements if len > 0 or the final abs(len) elements if len < 0.

begin has to be a valid index, and abs(len) elements must be available for copying. 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()
{
1    auto v = bit::vector<>::random(12);
    std::cout << "v:           " << v           << "\n";
2    std::cout << "v.sub(0, 4): " << v.sub(0, 4) << "\n";
3    std::cout << "v.sub(4):    " << v.sub(4)    << "\n";
4    std::cout << "v.sub(-4):   " << v.sub(-4)   << "\n";
5    std::cout << "v.sub(8, 4): " << v.sub(8, 4) << "\n";
}

1: Construct a vector of size 12 with a random fill.
2: Extract four elements starting at index 0.
3: Do the same thing using a shorthand notation.
4: Extract the final four elements using the shorthand notation.
5: Do the same thing by copying four elements starting at index 8.

Output

v:           [0 1 0 0 1 0 1 0 0 1 1 0]
v.sub(0, 4): [0 1 0 0]
v.sub(4):    [0 1 0 0]
v.sub(-4):   [0 1 1 0]
v.sub(8, 4): [0 1 1 0]

See Also