Consistency of reserved operators and bang patterns

[Isaac Dupree]

Twan van Laarhoven wrote:
> The bang pattern proposal [1] still allows (!) to be used as an 
> operator. I think there should be no difference in this regard between ! 
> and ~, since they are used in exactly the same location.
> 
> In my opinion the best thing would be to allow (~) and (@) as operators. 
> With the same restriction on definition as (!), i.e. they must be 
> defined in function style, not as an operator.
> 
> The change to the syntax would be to remove @ and ~ from the reserved 
> operators list [2],
>   reservedop -> .. | : | :: | = | \ | | | <- | -> | @ | ~ | =>
> making it
>   reservedop -> .. | : | :: | = | \ | | | <- | -> | =>

I agree - it confused me in the past that I couldn't define (@) or (~) 
operators.  Bang-pattern syntax being active will still change the 
meaning of

x ! y = z

of course.

> Oh, and while we are at it, I think (:) should also be removed as a 
> reservedop, there is no reason for it to be on that list.

Backwards compatibility requires that it be implicitly imported from 
Prelude even in a module that does "import Prelude ( )" (although Hugs 
is already broken in this regard).  And that makes it fairly useless as 
a non-reserved symbol.  If not for that issue, I agree.

Isaac