In ParaSail arrays are simply a special case of a container, and indexing is user-definable, so the index need not even be integers, and certainly there is no requirement that the first index be zero, or one, or any specific value. On the other hand, there are some pre-provided modules such as Vector and Univ_String which allow indexing, and some decision has to be made about whether to start with zero or one. Because of the Pascal/Ada/Modula heritage, the natural choice was to start with one.
However, there are algorithms where starting with zero is more natural, and there are certainly programmers who are more comfortable with starting indexing with zero, so we have recently added zero-based indexing versions of Vector and Univ_String, namely ZVector and ZString. So using ParaSail's half-open intervals, one can loop over the contents of a ZVector (or a ZString) with:
var ZV : ZVector<Univ_Integer> := [1, 3, 5, ...]; var Sum := 0; for I in 0 ..< Length(ZV) loop Sum += ZV[I]; end loop;