Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!spdcc!ima!esegue!johnl
From: johnl@esegue.segue.boston.ma.us (John R. Levine)
Newsgroups: comp.lang.misc
Subject: Re: PL/I Grammar
Keywords: PL/I, C, grammar, parser
Message-ID: <1989Oct18.012237.548@esegue.segue.boston.ma.us>
Date: 18 Oct 89 01:22:37 GMT
References: <2956@usceast.UUCP>
Reply-To: johnl@esegue.segue.boston.ma.us (John R. Levine)
Organization: Segue Software, Cambridge MA
Lines: 24

In article <2956@usceast.UUCP> sharp@usceast.UUCP (Harry Sharp) writes:
>	I am attempting to locate a copy of a PL/I or PL/C grammar to use
>in creating a PL/I to C translator.  This is a part of my Master's thesis.
>Does such a beast exist?  I have been told that PL/I cannot be parsed LALR.  
>Is this true? (I hope not.)

PL/I has no reserved words, which makes it pretty exciting to parse using
context-free methods.  You can, for example, call a variable READ or DECLARE.
Once you deal with that problem (by prescanning statements) the grammar
is supposed to be context free and yacc could probably handle it.

The ANSI PL/I standard has a BNF concrete syntax that is about 15 pages
of single-spaced text.  That's probably as good a place to start as any.

The semantics are messy, too.  Consider:

	A = B = C;

which compares B and C and sets A to '1'B if they are equal.  This is no
problem for yacc to handle, but it's a pain for humans.  What a language.
-- 
John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 864 9650
johnl@esegue.segue.boston.ma.us, {ima|lotus|spdcc}!esegue!johnl
Massachusetts has over 100,000 unlicensed drivers.  -The Globe