[m-dev.] Syntactic sugar for functor matching

[Simon Taylor]

On 06-Nov-2001, Peter Schachte <schachte at cs.mu.OZ.AU> wrote:
> > A related proposal is to allow `X @ f(...)' to denote pattern matching
> > with f(...) and having X unify with that argument on success.
> > 
> > For example, rather than writing
> > 
> > 	p(f(A, B, C)) :- X = f(A, B, C), ...
> > 
> > one could write
> > 
> > 	p(X @ f(A, B, C)) :- ...
> 
> Um, not to be stupid, but what's wrong with
> 
> 	p(X) :- X = f(A, B, C), ...
> 
> It's barely any more verbose, already legal, and requires no new syntax.
> Mercury doesn't even have Prolog's only-clauses-are-indexed flaw to motivate
> this sort of feature.

Readability. If the functor is in the clause head it makes it
clearer what is being indexed on and which case is being handled
in the clause.

Simon.
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