Original-Via: uk.ac.nsf; Sun, 10 Nov 91 02:23:26 GMT
a) If an instance declaration is given for a type T and class C, instance
declarations must also be given for T and all the superclasses of C.
b) If an instance declaration is given for a type T and class C, T is
automatically an instance of all the superclasses of C, although instance
declarations may be given for T and any superclasses of C for the purpose of
overriding defaults.
Which of these is better?
Consistent with the idea that one doesn't have to provide a method for
each operator when writing an instance decl, I'd vote for the latter
semantics. I.e., if you don't say anything then you get the default
membership and methods.
I think, however, that this would be a change from 1.0.
-Paul
