Thanks, the Scheme-version made it even clearer!
Cheers, Petter On Saturday 04 October 2003 13:53, you wrote: > On Sun, 5 Oct 2003 11:02:37 +0000 > > Petter Egesund <[EMAIL PROTECTED]> wrote: > > Hi & thanks for answering. > > > > I think I got it - the chaning of the functions lies in the last part > > of > > > > (\w -> if v==w then n else sto w) > > > > I am used to higher ordered functions from Scheme, but it was the > > delayed evaluation which played me the trick here. This function is > > built when updating, and not executed before asking value 'x'?! > > If by delayed evaluation you mean lazy evaluation then that has nothing > to do with it. Obviously the function isn't executed before asking the > value of 'x' because no function can run without it's argument(s). The > same representation will behave exactly the same in Scheme. > > (define init-store (lambda (key) 0)) > (define (lookup-store store key) (store key)) > (define (update-store store key value) > (lambda (lookup-key) > (if (equal? key lookup-key) > value > (lookup-store store lookup-key)))) > > Obviously, this will make the function taking lookup-key when > update-store is called (just like Haskell) and (just like Haskell) it > will only be executed when applied to a key to lookup. _______________________________________________ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
