[Gretl-devel] revision of index loop?

There's something I'd like to adjust about "index loops", that is, constructs of the form loop i=start..stop ... endloop At present such loops strictly increment the index by 1 at each iteration (and hence do not run at all if stop < start). I'd like to support decrement-by-1 in case stop < start, as in "loop i=10..1" (10,9,8,...,1). You can create such a "backwards" loop at present, either using the more flexible (but more cumbersome) "for" construct or by adding an auxiliary index, but it would be convenient to have the decrement case handled automatically. And it turns out that's easy to do. However, by itself this change would be backward-incompatible under some conditions. For example, if some hansl code is designed to run through combinations of elements of a vector or list of length n its skeleton might look like this: loop i=1..n -q loop j=i+1..n -q printf "(i,j) = (%d,%d)\n", i, j # access elements i and j endloop endloop When i reaches n the inner loop is not executed but under the proposed change it would be executed, giving j a value of n+1 and provoking an out-of-bounds error. One could say that the code above is buggy (the outer loop should really run from 1 to n-1) but it works OK at present. I'm therefore thinking that if we support the proposed variant perhaps it should require a --decrement option. Thoughts? Allin