Henning Thielemann writes:
On Thu, 19 Aug 2004, Sam Mason wrote:
class Foo t where encode :: String -> t decode :: t -> String
test = decode . encode
This currently fails, because the type checker insists on trying to figure out what its type should be - even though it shouldn't be needed.
In contrast to that,
test = encode . decode
should not fail. :-)
Rright. The source file: bz = read . show is accepted. It even "works": Ok, modules loaded: Main. *Main> :t bz bz :: forall a a1. (Show a1, Read a) => a1 -> a *Main> bz 8 8 But try to use it for something more exquisite: *Main> bz 8.23 *** Exception: Prelude.read: no parse Of course a signature put by hand helps. But then what's the advantage of classes? Actually, I would like to know what was the purpose of all that... Jerzy Karczmarczuk