Ambiguous type variable

22 Jan 2003

      Hi all, 

This works fine, as expected
...
f :: (Num a, Random a) => Int -> [a]
f = randomRs (0,1).mkStdGen
If I skip the type signature, though, I get the following error messages:
Main.hs:14:
    Ambiguous type variable(s) `a' in the constraint `Random a'
    arising from use of `randomRs' at Main.hs:14
    In the first argument of `(.)', namely `randomRs (0, 1)'
    In the definition of `f': (randomRs (0, 1)) . mkStdGen

Main.hs:14:
    Ambiguous type variable(s) `a' in the constraint `Num a'
    arising from the literal `1' at Main.hs:14
    In the first argument of `randomRs', namely `(0, 1)'
    In the first argument of `(.)', namely `randomRs (0, 1)'

Why exctly can't ghci figure how the type of f?

This just happens when loading the code from a file,
...
:t randomRs (0,1).mkStdGen
in ghci works fine.
J.A.

Ambiguous type variable

Jorge Adriano