Path: csiph.com!xmission!news.snarked.org!border2.nntp.dca1.giganews.com!nntp.giganews.com!news.iecc.com!.POSTED.news.iecc.com!nerds-end
From: rockbrentwood@gmail.com
Newsgroups: comp.compilers
Subject: Yacc with multiple entry points.
Date: Mon, 9 Dec 2019 16:13:06 -0800 (PST)
Organization: Compilers Central
Lines: 8
Sender: news@iecc.com
Approved: comp.compilers@iecc.com
Message-ID: <19-12-003@comp.compilers>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="96022"; mail-complaints-to="abuse@iecc.com"
Keywords: yacc, parse, comment
Posted-Date: 10 Dec 2019 13:23:10 EST
X-submission-address: compilers@iecc.com
X-moderator-address: compilers-request@iecc.com
X-FAQ-and-archives: http://compilers.iecc.com
Xref: csiph.com comp.compilers:2384

There is a lot of saving and code-reuse possible if multiple entry points are allowed in a parser generator. This can be done by a simple extension of the LR process, but does complicate the issue of end-markers a little.

You'll see brief mention of it, by the way, here on page 199 of the Lex and Yacc reference. https://books.google.com/books?id=vsHcnR4kXIAC&pg=PA199&lpg=PA199 authored by (... searching author page ...) Oh! The moderator, John!

[I put the same trick on pp 163-164 of flex&bison.  Fiddle the lexer
so it sends the parser a fake token when it starts and use initial
rules with the fake token to select the real entry point.  That works
in plain yacc or bison.  -John]