26 Sep
2001
26 Sep
'01
11:18 a.m.
nhc doesn't like the following program ...
type Option = Maybe
f :: Option a -> Maybe a f = id
main = putStrLn "hello world"
Transscript of the session ...
nhc98 --version /home/ralf/Lang/bin/nhc98: v1.08 (2001-09-25) [ config: ix86-Linux/ghc by malcolm@pc173.cs.york.ac.uk on 25 Sep 2001 ] nhc98 -v Bug.lhs nhc98comp +RTS -RTS -unlit -P/home/ralf/Lang/include/nhc98 ./Bug.lhs ./Bug.lhs /tmp/Bug.12000.hi /tmp/Bug.12000.hc
==================================== Error after type deriving/checking: Type error can not unify Prelude.Maybe with 1 and 0 arguments when binding final type to function at 4:8. The problem disappears if we change the type definition to
type Option a = Maybe a
Cheers, Ralf