On Fri, May 21, 2010 at 8:59 PM, R J wrote:

If I type "toEnum 5," the error I get is: <interactive>:1:0:     Ambiguous type variable `a' in the constraint:       `Enum a' arising from a use of `toEnum' at <interactive>:1:0-7     Probable fix: add a type signature that fixes these type variable(s) *Main>

Here the problem is not in your instance of Enum, but that GHCi doesn't know which instance of enum to use. In most code this isn't a problem, because the surrounding context often gives enough information for the type-checker to work with. But when there isn't enough context, you'll need to provide a type signature. Does "toEnum 5 :: Day" work? Antoine