Type operators in GHC

[Sjoerd Visscher]

Hi,

Note that nobody was suggesting two pragmas with incompatible behaviors, only to have just one symbol reserved to still be able to have type operator variables.

I do like your suggestion, although >--c--> is quite a bit longer than ~>.

Sjoerd

On Sep 17, 2012, at 6:28 PM, Iavor Diatchki wrote:

> Hello,
> 
> I think that it would be a mistake to have two pragmas with incompatible behaviors:  for example, we would not be able to write modules that use Conal's libraries and, say, the type nats I've been working on.
> If the main issue is the notation for arrows, has anoyone played with what can be done with the current (7.6) system?  I just thought of two variations that seem to provide a decent notation for writing arrow-ish programs.  The second one, in particular, mirrors the arrow notation at the value level, so perhaps that would be enough?
> 
> -Iavor
> 
> 
> {-# LANGUAGE TypeOperators, KindSignatures #-}
> module Test where
> 
> import Control.Category 
> 
> -- Variant 1: Post-fix annotation
> 
> type (a ---> b) c = c a b
> 
> f :: Category c => (x ---> y) c -> (y ---> z) c -> (x ---> z) c
> f = undefined
> 
> 
> -- Variant 2: Arrow notation
> 
> type a >-- (c :: * -> * -> *) = c a
> type c --> b                  = c b
> 
> infix 2 >--
> infix 1 -->
> 
> g :: Category c => (x >--c--> y) -> (y >--c--> z) -> (x >--c--> z)
> g = undefined
> 
> 
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