On Thu, Jul 16, 2009 at 8:22 PM, Thomas Hartman
I played with this a bit, and ok, it seems the difference between iterate' and iterate'' is
h _ = 2
tit' = head . drop 1 . iterate' h $ undefined tit'' = head . drop 1 . iterate'' h $ undefined
Exactly, iterate' first evaluates 'undefined' which is undefined. iterate'' returns 'undefined : iterate'' h 2'. Which then evaluates to: 'undefined : 2 : iterate'' h 2'. So both iterates are strict in their accumulator. They differ in when they force it. The former is more strict in that it forces its accumulator on entry while the latter is more lazy by first returning the accumulator and later forcing it.
(Bas wishes for a type system that can express the different strictness properties of these functions...)
Is this being worked on?
I have no idea. regards, Bas