[mercury-users] Type inheritance?

[John Griffith]

>> "TRD" == Tyson Richard DOWD <trd at students.cs.mu.oz.au> writes:

...

TRD> We are not working on subtyping at the moment - typeclasses are on the 
TRD> verge of implementation, and I think it would be best to use them for a
TRD> while before considering other changes to the type system.

I see the line in the file WORK_IN_PROGRESS:
    * Support for Haskell-style type classes

Could you give a brief description of type classes or references?

...

>> Is this possible?  If not, then is there a cost associated with the
>> constructors or do they get "compiled away"?  In other words, is there
>> an efficiency difference between (1) and (3)?
>> 

TRD> ...

TRD> Is this causing efficiency problems in your code, or are you just
TRD> curious?

Just curious.