<HTML>Thanks to both Ferguson and Mark for answering my questions!!! Quite helpful in getting me past the rut I was stuck in. >>When compiling multi-module programs, it can be difficult >>to manually figure out which interface files need to be generated, so we >>recommend you use mmake to do it automatically. E.g.: >> mmake main_module.depend >> mmake main_module Don't you just hate users that ignore the documentation. I had been using mmake a while back but when I ran into trouble I started using MMC (not that it helped). For some reason, I never went back to the recommended method. Works without a hitch using mmake. >>It sounds like you want abstract typeclass instances. In the interface >>section, mention the type and instance but don't give any definition, >>like so: >> :- type circleRecord. >> :- instance shapeClass(circleRecord). >> :- instance circleClass(circleRecord). Ok. Makes sense. Works as I expect it to now. Just overlooked the manner of declaring abstract types and it's relation with what I was trying to accomplish. >>I think it is because you have not given a mode for method draw/3 in the >>typeclass declaration in shape.m. You should try adding the line >> mode draw(in, di, uo) is det, That was the part I was trying to figure out. I couldn't figure out how to get the mode declared, and didn't think to put both the predicate and mode within the typeclass definition. Works like a charm when you declare the mode. I end up with typeclasses that look like: :- typeclass shapeClass(This) where [ func getX(This) = int, mode getX(in) = out is det, ..... cut ..... pred draw(This, io__state, io__state), mode draw(in, di, uo) is det ]. +++++++++ Ok. I'm good to go with the problems I had. One additional question I have concerns the write accessors. In my example, the read accessors work fine in the form of: getX_Circle(This) = This^x. I gather also that there is a write form of the accessor using the ':=' for the assignment but I can't figure out how to use it. Currently I'm writing it as: setX_Circle(circleRecord(_,Y,Radius), X) = circleRecord(X, Y, Radius). which spins off a new record based on the values in the input record. Anyhow, is there a way to use the set accessor to make this shorter, if not more efficient? Thanks. </HTML>