Wolfgang Jeltsch:
Am Mittwoch, 5. Dezember 2007 17:05 schrieb Simon Peyton-Jones:
[…]
Anyway, while on this subject, I am considering making the following change:
make all operator symbols into type constructors (currently they are type variables)
This would be highly problematic!
Concerning syntax, everything that holds for values should also hold for types. For values, identifiers starting with a capital letter and operators starting with a colon denote “constants”, everything else denotes variables. Exactly the same should hold for types since otherwise we would get a very confusing result. So we should keep things as they are concerning type constructors and type variables. And we should think about type functions being denoted by lower case identifiers and operators not starting with a colon because they are similar to non-constructor functions on the value level.
The problem is that Haskell 98 already messed that up. If type functions are to use lower-case letters, vanilla type synonyms should use lower case-letters; eg, type string = [Char] Unfortunately, such a change would break about every single Haskell program. So, unless we make some rather drastic changes breaking backwards compatibility, we will not be able to get an entirely clean solution. Manuel