Michael P Mossey wrote:
Thanks for the ideas, Adam. I still have a few questions.
Adam Bergmark wrote:
The reason my is available in the lambda \x -> my >>= \y -> W (x+y) has to do with scoping rules, Haskell (and almost all programming languages) use static scoping, meaning a variable defined in an outer function is available in the inner function, for instance, (\a -> \b -> (a,b)) 1 2 will evauate to (1,2) since a is bound to 1 in the outer lambda, and the inner one can refer to the outer one, if instead you write (\a -> \a -> (a,a)) 1 2 the result will be (2,2) since the innermost a will be used (no ambiguity here, but if shadowing is done by accident it can be hard to find the error).
Because the lambda is executed by the implementation of >>=, doesn't the concept closure still apply? That value of 'my' has to "get into" the other routine.
I think you are both right. AFAIU Adam comments on *visibility* of the variables, while you look more at the fact that you pass the lambda as an argument to (>>=). The lambda can "see" the variable my due to scoping, and (>>=) can trigger evaluation of the lambda due to closures. I'm looking forward to be corrected by someone who knows more about this than I do. /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe