"S. Alexander Jacobson" <[EMAIL PROTECTED]> asks:
> What does unresolved top level overloading mean in this context?
>
> > instance DBConnection OracleConnection where
> > openConnection dbms string = OracleConnection
>
> > test = openConnection Oracle "odbc:odbcURL"
>
> Test must be an OracleConnection.
> Why do I get an "unresolved top level overloading" error?
I think you're reasoning as follows:
There's only one instance of DBConnection therefore, when
Haskell sees a DBConnection context, it can assume it's that
instance.
That's the "closed world interpretation". ie All I have now is
all there ever will be. (cf "negation as failure" in Prolog)
Haskell uses the "open world interpretation" which assumes that
you could come along with a second instance any moment.
Alastair
