Neil Mitchell wrote:
I agree its definitely necessary in the case of classes. I don't see treating classes like the other functions as being consistent. Classes are fundamentally different - most functions have one module name, classes have three - this is a built in inconsistency. I can see advantages to being able to "spot" class dictionaries and recover precisely their original context information, I've wanted it before and this desugaring scheme, applied only to classes, would give that.
Of course it's still very easy in the case that it's applied everywhere. You split the string based on ';'. If you get two parts its a normal name, if you get 3 or 4 parts its a class instance. Three is possible because the instance dictionary is generated as Foo.Bar;Prelude.Eq;Foo.Bar.Baz = (,) Foo.Bar;Prelude.Eq;Foo.Bar.Baz;== Foo.Bar;Prelude.Eq;Foo.Bar.Baz;/=
Don't you then pay to create a thunk, then evaluate it later? I thought that this was one of the main costs saved by strictness, which wouldn't be saved by a case transformation.
Conceptually, no case f x of _ -> ... is a perfectly reasonable description to the backend that 'f x' should be compiled strictly (i.e. without thunks).
I would have thought the best encoding would be:
Foo.Bar;Foo.Bar.Baz;Prelude.Eq.==
OR
Prelude.Eq;Foo.Bar.Baz;Foo.Bar.==
In the first the rule for extracting module names is "up to the first ; or last .", in the second its "skip all bits before ;" - and I'm leaning towards the first. I read the first as "hey, I'm located in Foo.Bar, I operate over Foo.Bar.Baz and I'm really just a type specific version of Prelude.Eq.=="
Yeah that would be fine, don't forget that the class dictionary is Foo.Bar;Foo.Bar.Baz;Prelude.Eq if that has any bearings on trying to understand what things are.
Whatever scheme we do go with, I suggest a coreFunModule function be added which obtains the module from a function name, and assuming dictionaries are unambiguous, coreFunDictionary to split up the pieces.
or even 'coreModule' which would also work for data types. 'coreFunInstance' is possibly a better name than 'coreFunDictionary'. Cheers Tom