Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-lcc!lll-winken!uunet!munnari!vuwcomp!dsiramd!marcamd!aucsv!ok
From: ok@aucsv.UUCP (Richard Okeefe)
Newsgroups: comp.lang.prolog
Subject: Re: Committed Choice
Summary: not identical
Keywords: cut if-then-else
Message-ID: <192@aucsv.UUCP>
Date: 30 Mar 89 06:05:54 GMT
References: <11500012@hpldola.HP.COM> <733@gould.doc.ic.ac.uk> <18798@adm.BRL.MIL>
Organization: Computer Science Dept.,University of Auckland,New Zealand
Lines: 24

: In article <8209@russell.STANFORD.EDU> pereira@russell.UUCP (Fernando Pereira) writes:
: :	repeat,
: :		{ Body }
: :		( <exit condition> -> !
: :		; <continue condition> -> fail
: :		).
In article <18798@adm.BRL.MIL>, broome@adm.BRL.MIL (Paul Broome ) writes:
: 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>).


They don't do the same thing.  When we're talking about cuts and repeats,
we're in Imperative land.  Consider then that the first version calls the
body then the exit condition and then the continuation condition.  While
the second version is missing the body and calls the continuation
condition before the exit condition.  (Actually, the second version has
mixed the body and continuation condition up.)