19 Aug
2004
19 Aug
'04
6:39 p.m.
karczma wrote:
Don't forget that this is the toplevel business, not a universal "disease". GHCi says
Prelude> :t (show . read) (show . read) :: String -> String
and doesn't complain. But if you define
bz = show . read
the attempt to load this definition (file: ctest.hs) results in:
ctest.hs:3: Ambiguous type variable `a' in these top-level constraints: `Read a' arising from use of `read' at ctest.hs:5 `Show a' arising from use of `show' at ctest.hs:5 Failed, modules loaded: none. Prelude>
OK, you've got me interested! Why doesn't GHCi complain about the ambiguity?
So, as one of my friends used to say: it should be obvious for everybody that what is obvious for one, need not be obvious for the others...
Suitably abstruse!