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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