r
          If NULL: same as zero
END   --- If positive:
            the exclusive ending index of the slice
          If negative:
            the exclusive ending index of the slice from
            the end of the vector.
          If NULL: same as the length of the vector

Note that this creates a displaced vector pointing to the
original vector. It thus shares the data with the original
vector, and does not support a STEP size other than 1.

See <a href="#FUNCTION%20ARRAY-UTILS%3ASLICE" class="xref">SLI