TJ said:
I went through the entry on laziness on the wikipedia wikibook. Very nice. The wikibook sure has grown a lot since I last visited.
Thanks for the link. I hadn't seen that before. Although it covers irrefutable (lazy) pattern matching in the second section, it does appear to miss the point that let bindings are always irrefutable. Thus, there is no difference between these two: let (x,y) = foo in ... let ~(x,y) = foo in ... I need to have a closer look when I have some more time, but I think this might have lead to some inaccuracies in the first section (Thunks and WHNF). FYI, the Haskell 98 Report defines the non-recursive let binding in terms of a case expression with an irrefutable pattern match. So, the following are equivalent: let (x,y) = foo in ... case foo of ~(x,y) -> ... But note that function arguments are defined in terms of case expressions (whose patterns are refutable), so the following are *not* equivalent (example from the wikibook): let f (x,y) = 1 in f undefined let f ~(x,y) = 1 in f undefined Confused again?
I believe I've got it now. By it I mean the understanding of laziness in Haskell. Even though Haskell is, strictly speaking, not lazy, but non-strict. "It" being but read and thought about, and not practiced, might prove _itself_ to become Undefined as I evaluate it further. :D
Nicely put. I think you are getting it. :-)