[mercury-users] list functor style functions

[Ralph Becket]

> Obviously the error message here is not a good one.
> But what the compiler is complaining about is the type `T'
> in the second argument of the instance declaration for `sequence'.
> The error is that this does not meet our current set of restrictions
> on instance declarations, namely that types in instance declarations
> must all be of the form `<typeconstructor>(<TypeVar1>, ..., 
> <TypeVarN>)'
> for some N >= 0.

I'll submit a bug report for that one, then.  I tried the following just
for kicks (it's illegal under the current restrictions)...

:- type thing(T) == T.

:- instance sequence(my_list(T), thing(T)) where [...].

And the compiler threw an exception.

Hmm, this restriction (no free type variables as instance arguments) could
be a bit of a pain.

Ralph
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