Function __npy_pos_remainder

numpy/core/src/multiarray/iterators.c:1618–1638

For an array x of dimension n, and given index i, returns j, 0 <= j < n * such as x[i] = x[j], with x assumed to be mirrored. For example, for x = * {1, 2, 3} (n = 3) * * index -5 -4 -3 -2 -1 0 1 2 3 4 5 6 * value 2 3 3 2 1 1 2 3 3 2 1 1 * * _npy_pos_index_mirror(4, 3) will return 1, because x[4] = x[1]*/

 *
 * _npy_pos_index_mirror(4, 3) will return 1, because x[4] = x[1]*/
static inline npy_intp
__npy_pos_remainder(npy_intp i, npy_intp n)
{
    npy_intp k, l, j;

    /* Mirror i such as it is guaranteed to be positive */
    if (i < 0) {
        i = - i - 1;
    }

    /* compute k and l such as i = k * n + l, 0 <= l < k */
    k = i / n;
    l = i - k * n;

    if (_NPY_IS_EVEN(k)) {
        j = l;
    } else {
        j = n - 1 - l;
    }
    return j;
}
#undef _NPY_IS_EVEN

#define _INF_SET_PTR_MIRROR(c) \