[mercury-users] Indexing & operational semantics

Peter Schachte schachte at cs.mu.OZ.AU
Wed Feb 2 15:05:30 AEDT 2000

On Wed, Feb 02, 2000 at 12:24:06PM +1300, Richard A. O'Keefe wrote:
> Peter Schachte wrote:
> 	(I'm using && as sequential conjunction for this
> 	example.)  The only subtlety is in choosing the precedence for &&.
> 	Should a, b && c, d associate as (a,b) && (c,d) or as a, (b && c), d?
> Either way is bound to confuse someone.

It's a danger, but I think it manageable.  It's much like `,' and `;'
now:  the solution is good layout conventions.  If I write, eg,

	(   b
	&&  c

	(   a,
	&&  c,

the meaning is pretty clear.  I guess now I'm arguing for making `,'
bind tighter than `&&'; it just seems to work out better that way.

>  I think the answer is to borrow
> an idea from Ada, and say that any given conjunction may contain all
> `commutative and's or all `sequential and's, but it's a syntax error to
> mix them.

That seems a bit extreme.

Peter Schachte                     How does a project get to be a year late?
mailto:schachte at cs.mu.OZ.AU        ... One day at a time. -- Frederick
http://www.cs.mu.oz.au/~schachte/  Brooks, _The Mythical Man Month_ 
PGP: finger schachte at  
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