19 Oct
2006
19 Oct
'06
3:27 p.m.
On Thu, Oct 19, 2006 at 01:37:16PM -0400, Cale Gibbard wrote:
Why is this so? I'd have thought that the equality function for lists only forces evaluation of as many elements from its arguments as to determine the answer.
In order to determine if [1..length xs] has an element at all, you have to evaluate length xs, which involves forcing the entire spine of xs, because integers can't be partially evaluated. Computing lengths of lists is a great way to introduce strictness.
Right, so if Ints were represented as a datatype with Succ and Zero constructors (so integers could be partially evaluated), then the version with length would behave nicely on large and infinite lists :-) Best regards Tomasz