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From: ddgg0881@uxa.cso.uiuc.edu
Newsgroups: comp.lang.prolog
Subject: different Prologs?
Message-ID: <111000002@uxa.cso.uiuc.edu>
Date: 9 Oct 89 09:39:26 GMT
Lines: 22
Nf-ID: #N:uxa.cso.uiuc.edu:111000002:000:842
Nf-From: uxa.cso.uiuc.edu!ddgg0881    Oct  8 22:00:00 1989



I have two questions about Prolog implementations:

1. I've discovered one implementation that gives 3 solutions to
member(a,[a,a,a]) even though there aren't 3 ways to instantiate
variables. Another implementation I've used gives only one solution.
Which way is standard? Are there arguments for doing things one way
or the other?

2. I find reading text files very painful in Prolog because you
always have to keep a lookahead character. This way of doing things
doesn't feel like Prolog. One of the main selling points of Prolog
is the efficient way that it backtracks upon failure. Are there any
implementations of Prolog that allow 'get' or 'get0' to backtrack
and unread characters?

Dale Gerdemann
University of Illinois, Dept of Linguistics
Cognitive Science Group, Beckman Institute
dale@tarski.cogsci.uiuc.edu
d-gerdemann@uiuc.edu