At 20:15 17/06/03 -0400, Derek Elkins wrote:
On Tue, 17 Jun 2003 21:01:57 +0100 Graham Klyne <gk@ninebynine.org> wrote:
I'm convinced I've seen a function like this somewhere: [a->b] -> a -> [b] but cannot remember where. Or maybe: Monad m => m (a->b) -> a -> m b ?
I could roll my own (*), but I'm trying not to duplicate standard library functions is I can help it. Any pointers?
The closest function I see is ap :: Monad m => m (a -> b) -> m a -> m b
That's the one I was trying to remember! Thanks.
Also you may want to check out the Haskell reference at zvon.org, it's indexed by type as well.
Ah! Very useful. Thanks again.
flist :: [a->b] -> a -> [b] flist fs a = map (flip ($) a) fs
or much nicer (IMO) flist fs a = map ($ a) fs
Ah, yes, I'd not quite grasped that sections can be used "either way" round like this. I agree that's much neater, and this way of combining $ and map an idiom that I think could be used in other ways.
or breakin' out the point-free style, flist = flip (map . flip ($)) -- okay, so I wouldn't recommend this
I keep on reading about this "point free style", but can't find any discussion of it. Are there any pointers (sic) ? #g ------------------- Graham Klyne <GK@NineByNine.org> PGP: 0FAA 69FF C083 000B A2E9 A131 01B9 1C7A DBCA CB5E