On Friday 01 September 2006 11:44, Neil Mitchell wrote:
Hi
func2 f g l = filter f (map g l) is func2p f g = (filter f) . (map g)
func2 = (. map) . (.) . filter
Again, how anyone can come up with a solution like this, is entirely beyond me...
To answer part of the OP's question, it's always possible to rewrite a lambda term using point-free style (using a surprisingly small set of basic combinators). The price you pay is that the new term is often quite a bit larger than the old term. Rewriting complicated lambda terms as point-free terms is often of, em, dubious value. OTOH, it can be interesting for understanding arrows, which are a lot like monads in points-free style (from what little experience I have with them). BTW, the process of rewriting can be entirely automated. I assume the lambdabot is using one of the well-known algorithms, probably tweaked a bit. Goolge "combinatory logic" or "Turner's combinators" if you're curious.
Thanks
Neil
-- Rob Dockins Talk softly and drive a Sherman tank. Laugh hard, it's a long way to the bank. -- TMBG