Newsgroups: comp.lang.prolog
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From: paulward@torolab.vnet.ibm.com (paulward)
Subject: Re: Otherwise?
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Message-ID: <PAULWARD.95Feb17080302@skyhawk.torolab.vnet.ibm.com>
In-Reply-To: pereira@radish.research.att.com's message of Thu, 16 Feb 1995 18:10:05 GMT
Date: Fri, 17 Feb 1995 13:03:01 GMT
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References: <D3x65E.JED@uceng.uc.edu> <PEREIRA.95Feb16131005@radish.research.att.com>
Organization: IBM Toronto Lab
Followup-To: comp.lang.prolog


Fernando> In article <D3x65E.JED@uceng.uc.edu> skutnar@washington.occ.uc.edu (Stephen Kutnar) writes:
Fernando> 	   Does anyone know what the the "otherwise" statement does in Quintus?
Fernando>    I assume it has something to with conditionals, but am not sure how to sub-
Fernando>    stitute for its behavior in a non-Quintus environment (C-Prolog).
Fernando> It's just another spelling for "true", added to make conditionals
Fernando> supposedly more readable

Fernando> 	( p1 -> q1
Fernando> 	; p2 -> q2
Fernando> 	...
Fernando>         ; otherwise -> r )

It has relevance in a concurrent/committed choice context, where it
forces a sequential interpretation of the clauses.  That is to say, if
all clauses may be tried concurrently, a simple "true" will succeed,
committing to that clause, where the "otherwise" clause may only be
evaluated after all prior clauses have failed.
-- 
-- Paul (paulward@torolab.vnet.ibm.com)
DB2/PE Development.
