outStanza | (isMessage) = outMessage | (isPresence) = outPresence | (isIQ) = outIQ
Why such a style doesn't work, so I must write ugly code like that:
outStanza a | (isMessage a) = outMessage a | (isPresence a) = outPresence a | (isIQ a) = outIQ a
so, guards can't be useful in point-free function definitions in any way
You just have to avoid all those pointless language constructs that let mere Haskellers deal with points, and define your own: import Control.Monad import Data.Maybe import Control.Arrow((&&&)) g |= rhs = uncurry (>>) . ((guard . g) &&& (return . rhs)) a +++ b = uncurry mplus . (a &&& b) (=|) = (fromJust .) outStanza = (=|) (((=="m") |= ("message: "++)) +++ ((=="p") |= ("presence: "++)) +++ ((=="i") |= ("iq: "++)) ) Sorry about mentioning those Strings, but then the names shouldn't really mention the points (Stanza/Message/..), either, right? Or have I missed the point of this exercise?-) Claus