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From: raghutp@hubcap.clemson.edu (Raghu Toppur)
Newsgroups: comp.lang.prolog
Subject: Re: Looking for source code for Prolog (general)
Summary: parsers for PROLOG
Message-ID: <1991May2.155052.16813@hubcap.clemson.edu>
Date: 2 May 91 15:50:52 GMT
References: <1991Apr30.075951.9679@news.iastate.edu> <5525@goanna.cs.rmit.oz.au>
Organization: Clemson University
Lines: 17

In article <5525@goanna.cs.rmit.oz.au>, ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes:
> 
> You cannot parse Prolog using Yacc, because Prolog is not an LR(1)
> language.  It is possible to construct a Prolog term of any desired
> length such that the interpretation of the first token (atom? prefix op?)
> cannot be determinee until the last token has been seen, which means
> that Prolog is not LR(k) or LL(k) for _any_ k.
>     
Surely there is a "subset" of Prolog language for which an LR(1) grammar
could be used ? My question is briefly as follows : What aspects of Prolog 
syntax cause it to be non-LR(1) ? Is the "op" predicate considered central to the definition of Prolog ? That would mean that the yacc-parser I've been using
so far isn't fully complete (yet!) and never will be.

--
Raghu Toppur                             e-mail : raghutp@hubcap.clemson.edu
                                         Dept of Comp Sc,
Phone : 803-656-2637                     Clemson University, Clemson, SC 29631.