Chris I'm slowly getting around to this. Design questions: (A) I think it would be a good compromise to declare that operators like "+" are type *constructors* not type *variables*. So S+T would be a type. That's slightly inconsistent with value variables, but it's jolly useful. So only alphabetic things would be type variables. It's very clunky having to write S :+: T (B) One wants to declare fixities for type constructors, and that gets them mixed up with their value counterparts. My suggestion: disamiguate with a compulsory 'type' keyword infix 6 type + infixl 9 type * Or should it be 'data'? Or should it depend how + and * are declared? (C) The other place they can get mixed up is in import and export lists. I can think of several solutions (i) module Foo( + ) where ... means export the type constructor (+); currently illegal in H98 module Foo( (+) ) where ... means export the variable (+). This seems a bit of a hack. (ii) Use the 'type' keyword, rather like 'module': module Foo( type + ) where data a+b = A a | B b or module Foo( type +(A,B) ) where data a+b = A a | B b [I think 'type' is better than 'data' because we want to hide the distinction in an export list.... or do you think we should use the same keyword as the one in the defn?] Similarly on import lists. (D) I suppose one might want infix notation for type variables too: data T a = T (Int `a` Int) but maybe that's going too far? Simon | -----Original Message----- | From: Okasaki, C. DR EECS [mailto:Christopher.Okasaki@usma.edu] | Sent: 03 May 2002 14:09 | To: 'glasgow-haskell-users@haskell.org' | Subject: infix type constructors | | | I'm not sure how long this has been implemented in GHC, | but I just noticed that infix type constructors are allowed, | as in | | data a :- b = ... | | The syntactic asymmetry between type constructors and | data contructors has bothered me for a while, so this | is a welcome change! However, this syntax seems to | be supported for "data" and "newtype" declarations, | but not for "type" declarations. For example, | | type a :- b = ... | | does not seem to be allowed. Is there a reason for this? | Or was it just an oversight? | | -- Chris | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-| haskell-users |