Daniel Bastos wrote:
So it sounds correct to say that a closure is a function that brings an environment with it, such as variables defined outside of it.
With this ability, we can construct functions on the fly because a function can return a closure which is amended and, say, returned again another closure more fully specified.
Hello. This was actually a request for comments. Though I didn't say it. Does that sound correct? Any comments? Thanks much.
Yes, that's pretty much correct. The simplest example of a closure is indeed foo = add 3 where add = \x y -> x + y Reduction to weak head normal form yields foo = let x = 3 in \y -> x + y which means that foo is a function \y -> x + y paired with the value of the free variable x . Note that closures are an implementation detail. From a semantic point of view, add 3 can readily be understood as an ordinary function. Regards, apfelmus -- http://apfelmus.nfshost.com