On Fri, Feb 19, 2010 at 10:42 PM, wren ng thornton
Sean Leather wrote:
The second option approaches the ideal pointfreeness (or pointlessness if you prefer), but I'd like to go farther:
(...) :: (c -> d) -> (a -> b -> c) -> a -> b -> d
(...) f g x y = f (g x y) infixr 9 ...
I go with infixl 8 personally. It seems to play better with some of the other composition combinators.
In a somewhat different vein than Oleg's proposed general composition, I've particularly enjoyed Matt Hellige's pointless fun combinators[0]. I have a version which also adds a strict application combinator in my desiderata package[1] so we can say things like:
foo $:: bar ~> baz !~> bif
which translates to:
\a b -> bif (foo (bar a) (baz $! b))
These combinators are especially good when you don't just have a linear chain of functions.
Thanks! I'm glad to know that people have found this approach useful. In cases where it works, I find it somewhat cleaner than families of combinators with (what I find to be) rather obscure names, or much worse, impenetrable sections of (.). We can write the original example in this style: fun = someFun someDefault $:: id ~> id ~> runFun but unfortunately, while it's both pointfree and fairly clear, it isn't really an improvement over the pointful version, IMHO. Matt