Comments on: Building a Generic Statistics Library, Part 3: Fold

By: Arioch

Arioch — Wed, 26 Oct 2011 16:34:21 +0000

hhh, in this sense. I see.

BTW, i guess if You’d not try to simplify things and make value and accumulator have different types, then maybe you’d be easier to point difference in FoldL and FoldR

However, that would ask for another example, like MakeString (list=(1,2,3,4), separator=’, ‘)

By: Craig Stuntz

Craig Stuntz — Tue, 25 Oct 2011 21:40:17 +0000

You could fold over an unordered list, but you could not count on a specific result if the function you pass to fold isn’t communitive. Consider string concatenation, e.g. For an example from math, think of the operation on a non-Abelian group.

By: Arioch

Arioch — Tue, 25 Oct 2011 21:13:03 +0000

why can’t be Fold over set ?
As soon as the item can be expelled from set it is almost the same, as expelling Head from List.

Speed might be very different (especially for immutable containers), but mathematically it seems to be the same.