infix type operators

Simon Peyton-Jones simonpj at microsoft.com
Wed Mar 9 03:47:38 EST 2005


Yes, that makes sense.  I think I will do that.  Whether it'll make it
into 6.4 is doubtful

S

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org
[mailto:glasgow-haskell-users-
| bounces at haskell.org] On Behalf Of Ross Paterson
| Sent: 08 March 2005 16:29
| To: glasgow-haskell-users at haskell.org
| Subject: infix type operators
| 
| The User's Guide says:
| 
| 	The only thing that differs between operators in types and
| 	operators in expressions is that ordinary non-constructor
| 	operators, such as + and * are not allowed in types.  Reason:
| 	the uniform thing to do would be to make them type variables,
| 	but that's not very useful.  A less uniform but more useful
thing
| 	would be to allow them to be type constructors.  But that gives
| 	trouble in export lists.  So for now we just exclude them.
| 
| Conal has pointed out that the uniform thing would be useful for
| general arrow combinators:
| 
| 	liftA2 :: Arrow (~>) =>
| 		(a -> b -> c) -> (e ~> a) -> (e ~> b) -> (e ~> c)
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