[mercury-users] Syntactic sugar for higher order types and mo des

[Tyson Dowd]

On 26-Jul-2000, Richard A. O'Keefe <ok at atlas.otago.ac.nz> wrote:
> Tyson Dowd suggests changing the mode operator ->
> 
> 	For backwards compatibility we could accept :: and -> for a while, but
> 	if using == some other operator should be used.  Wouldn't `-' work OK?
> 	
> 	:- mode foo == free - ground.
> 	:- mode foopair == (free - ground) - (ground - ground).
> 	
> '-' really doesn't suggest sequence; if anything I'd expect Later-Earlier.
> One possibility is to use a word:
> 	:- mode foo == free then ground.
> 	:- mode foopair == (free then ground) - (ground then ground).

Actually in this case it would be 
 	:- mode foopair == (free - ground) then (ground - ground).

So perhaps this proves your point that the `-' syntax isn't suggestive
enough.

But I think `then' has a higher precedence than `==' so that's not going
to parse very nicely.

> Another possibliity is to use >>
> 	:- mode foo == free>>ground.
> 	:- mode foopair == free>>ground - ground>>ground.

`>>' has the right precedence already, and isn't a bad choice.

 	:- mode foo == free >> ground.
 	:- mode foopair == (free - ground) >> (ground - ground).

I'd be perfectly happy with this.
 
> Whatever is chosen, I think it should suggest by its name or its form
> which state is "before" and which is "after".

-- 
       Tyson Dowd           # 
                            #  Surreal humour isn't everyone's cup of fur.
     trd at cs.mu.oz.au        # 
http://www.cs.mu.oz.au/~trd #
--------------------------------------------------------------------------
mercury-users mailing list
post:  mercury-users at cs.mu.oz.au
administrative address: owner-mercury-users at cs.mu.oz.au
unsubscribe: Address: mercury-users-request at cs.mu.oz.au Message: unsubscribe
subscribe:   Address: mercury-users-request at cs.mu.oz.au Message: subscribe
--------------------------------------------------------------------------