seg.spad line 50 [edit on github]
This category provides an interface for expanding segments to a stream of elements.
expand(l..h by k) creates value of type L with elements l, l+k, ... lN where lN <= h < lN+k. For example, expand(1..5 by 2) = [1, 3, 5].
expand(l) creates a new value of type L in which each segment l..h by k is replaced with l, l+k, ... lN, where lN <= h < lN+k. For example, expand [1..4, 7..9] = [1, 2, 3, 4, 7, 8, 9].
map(f, l..h by k) produces a value of type L by applying f to each of the successive elements of the segment, that is, [f(l), f(l+k), ..., f(lN)], where lN <= h < lN+k.