You need to monomorphize the result before printing: main = print $ ((square . 4) :: Alpha ()) Presumably you will apply (square . 4) at some point to a concrete state at some point, and you wouldn't need to provide the type explicitly. Greg Buchholz wrote:
Dan Weston wrote:
How about:
Hmm. I'm probably being dense today, but when I add the following definitions to your program...
main = print $ (square . 4) () square (a,b) = (a*a,b)
...I still get the same error...
No instance for (Num (() -> (t, t1))) arising from the literal `4' at weston.hs:5:25 Possible fix: add an instance declaration for (Num (() -> (t, t1))) In the second argument of `(.)', namely `4' In the second argument of `($)', namely `(square . 4) ()' In the expression: print $ ((square . 4) ())
...maybe you could show me your implementation of "main" and "square" to help nudge me in the right direction. (I'm using ghc-6.6)
Thanks,
Greg Buchholz _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe