🚀 go-pugleaf

Here's one alternative I've seen that's only slightly cleaner:  Define

	repeat(Body,Until) :-
		repeat,
		Body,
		Until,
		!.
		
Then we can accomplish the same thing with

	...
	repeat(<continue condition>, <exit condition>).
	

-Paul


In article <8209@russell.STANFORD.EDU> pereira@russell.UUCP (Fernando Pereira) writes:
:In Edinburgh-family Prolog systems, the scope of a cut is the whole
:clause in which it appears, even it the cut is inside a conditional.
:This is a very useful control behavior, messy to simulate with cuts
:that stay inside the scope of conditionals. For example, the following
:is a common way of terminating a repeat/fail loop:
:
:	...
:	repeat,
:		...
:		( <exit condition> -> !
:		; <continue condition> -> fail ).
:
:I will agree with anybody that this is not a pristine example of
:declarative programming, but such things *are* needed in the imperfect
:logic-programming languages we have today. I also appreciate that we
:could move the cut to after the conditional with the same result, but
:there are more complicated situations, which I don't have the time now
:to discuss, in which that alternative is not available.
:
:Fernando Pereira
:AI Center
:SRI International
:pereira@ai.sri.com



Paul Broome
broome@brl.arpa