Different code for different modes

[Peter Schachte]

On Thu, 22 Jan 1998, Fergus Henderson wrote:

> How about the following alternative syntax?
> 
> 	p(X::in, Y::out) :- p_1(X).
> 	p(X::out, Y::in) :- p_2(X).
> 	...
> 

Presumably you mean:

	p(X::in, Y::out) :- p_1(X, Y).
	p(X::out, Y::in) :- p_2(X, Y).
	...

Yes, this is better still, because it doesn't require one to write p_1, p_2,
etc. in any particular way.  This would be very nice.

As to presuming such preds impure, that would be acceptable, though I see
less reason to presume such a pred impure than to presume a pragma c_code
version of the same thing impure.  I wouldn't want to do this terribly
often, so I could cope with promising each such pred pure if it is. 


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