[Switched to haskell-cafe] At 13:24 13/10/04 -0400, Jacques Carette wrote:
-- It's kind of like an converse map.
I have attempted, unsuccessfully, to write flist above in a point-free manner. Is it possible?
Of course it is, but why? flist = flip (map . flip ($))
Some functions are simpler point-free, others are simpler with points. I was curious about this one (I like the pointwise version better).
Also, the statement "It's kind of like a converse map" becomes quite clear from the point-free way to write it, while still not so obvious in the pointwise version.
The point-free form can be deduced thus, I think: flist fs a = map ($ a) fs (flip flist) a fs = map ($ a) fs -- swap flist args (flip flist) a = map ($ a) -- redundant arg (flip flist) a = map ((flip ($)) a) -- expand section (flip flist) a = (map . (flip ($))) a -- definition of . (flip flist) = map . (flip ($)) -- redundant arg flist = flip (map . (flip ($))) -- move flip to RHS #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact