Newsgroups: comp.lang.prolog
Path: utzoo!utgpu!watserv1!maytag!watdragon!ebspencer
From: ebspencer@watdragon.waterloo.edu (Bruce Spencer)
Subject: Re: Answer to freeware prolog
Message-ID: <1990Nov15.172248.16890@watdragon.waterloo.edu>
Organization: University of Waterloo
References: <31876@netnews.upenn.edu>
Distribution: na
Date: Thu, 15 Nov 90 17:22:48 GMT
Lines: 58

This article may be of interest to anyone following the search for 
a free public domain prolog for the IBM PC. 

In article <31876@netnews.upenn.edu> vinson@linc.cis.upenn.edu (Jack Vinson) writes:
>Well, here's what I found out about free prolog.  Thanks for your
>responses.
...
> Anyway, there is a Prolog called PDPROLOG that runs on IBM PCs.  The low-end
> version is public-domain; higher-level versions have increasinly higher costs.
> The low end version seems adequate for instructional use.  Last I checked, it
> was available via anonymous FTP from wuarchive.wustl.edu from the directory
> /mirrors/msdos/prolog
...
>Jack Vinson				vinson@linc.cis.upenn.edu


I did FTP PDProlog from wuarchive.wustl.edu in the directory
/mirrors/msdos/prolog and I have two comments that might be of
interest to others looking for a public domain prolog for IBM PC's:
	
	First, it appears to be quite old, 1986 is the date of the
copyright. 

	There appears to be a bug in this version. For instance
I ran append(X, Y, [a,b,c]) and got the following answers:
X = [],
Y = [a,b,c]	

X = [a],
Y = [b,c]

X = [a,b],
Y = [c]

X = [a,b,c],
Y = L_17

Of course, the first three are right, but the fourth answer should
have been
X = [a,b,c]
Y = []

I am guessing that L_17 is some internal name for a variable.
	

As a result I have decided NOT to use this system for my introductory
course in logic programming. If there is a better version available
I may change my mind. 

Does anyone know of a more recent version of PDProlog than what is
archived at wuarchive.wustl.edu? 

Thanks
	Bruce Spencer

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Bruce Spencer                    |     CS Faculty, University of New Brunswick
ebspencer@watdragon.waterloo.edu | Fredericton, New Brunswick, Canada, E3B 5A3