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From: fuchs@ifi.unizh.ch
Newsgroups: comp.lang.prolog
Subject: Re: '->' operator
Message-ID: <1991Jan4.143017.29823@ifi.unizh.ch>
Date: 4 Jan 91 14:30:17 GMT
References: <1991Jan4.030918.24996@athena.cs.uga.edu> <16491@cs.utexas.edu> <1991Jan4.061142.26941@athena.cs.uga.edu>
Reply-To: fuchs@ifi.unizh.ch
Organization: University of Zurich, Department of Computer Science
Lines: 23

In article <1991Jan4.061142.26941@athena.cs.uga.edu> mcovingt@athena.cs.uga.edu (Michael A. Covington) writes:
>In article <16491@cs.utexas.edu> bradley@cs.utexas.edu (Bradley L. Richards) writes:
>>
>>Ah, but if '->' is intended to be an implementation of the procedural
>>if-then-else (or, in the case I'm concerned with, if-then) then it
>>should still succeed if the condition is false.  After all, procedurally
>>execution will continue following an if statement whether or not the
>>condition in the if was true.
>
>   Ah. I had not quite realized that it didn't. So (p -> q) fails if 
>   p fails?
>   
>>So either under the logical interpretation or under the procedural one
>>it seems to me that the Quintus '->' works improperly.
>>
>   I hope R. A. O'Keefe (the most vocal defender of "->"; he may
>   even have invented it) will join this discussion.
>   

I will not anticipate Richard O'Keefe's answer, but P -> Q works as if
implemented as P, !, Q.

   --- nef