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From: kam@druhi.UUCP (MorrisseyKA)
Newsgroups: comp.lang.prolog
Subject: Re: cut for meta-interpreter
Message-ID: <1861@druhi.UUCP>
Date: Mon, 20-Apr-87 16:17:54 EST
Article-I.D.: druhi.1861
Posted: Mon Apr 20 16:17:54 1987
Date-Received: Thu, 23-Apr-87 03:29:05 EST
References: <6681@bu-cs.BU.EDU>
Organization: AT&T Information System Labs, Denver, Co
Lines: 21
Keywords: cut,ancestor cut,meta-interperter
Summary: a solution

In article <6681@bu-cs.BU.EDU>, raf@bu-cs.UUCP writes:
> Does anybody know how to implement PROLOG meta-circular interpreter
> with cut without using ancestor cut? Is there a clean way to implement
> (both at PROLOG level and at meta-interpreter level) ancestor cut?

One solution is:

	execute(true) :- !.
	execute((P,Q)) :- !, execute(P), execute(Q).
	execute(P) :- clause((P:-Q)), execute(Q).
	execute(P) :- P.

It is attributed to Pereira (don't know which one) and can be found on
page 157 of:

	HOW TO SOLVE IT WITH PROLOG
	4th edition
	by H. Coelho, J. Cotta, and L. Pereira
	Lisbon, 1985

Karen A. Morrissey