Re: Backtracking and parsing tools

"Jim Cordy" <cordy@mac.com>
12 Jan 2005 22:56:35 -0500

          From comp.compilers
Related articles
Backtracking and parsing tools adrian@sartre.cs.rhul.ac.uk (A Johnstone) (2004-10-02)
Re: Backtracking and parsing tools vbdis@aol.com (2004-10-04)
Re: Backtracking and parsing tools tarvydas@attcanada.ca (Paul Tarvydas) (2004-10-09)
Re: Backtracking and parsing tools cordy@mac.com (Jim Cordy) (2005-01-12)
| List of all articles for this month |
From: "Jim Cordy" <cordy@mac.com>
Newsgroups: comp.compilers
Date: 12 Jan 2005 22:56:35 -0500
Organization: http://groups.google.com
References: 04-10-021
Keywords: parse
Posted-Date: 12 Jan 2005 22:56:35 EST

The TXL language has full parser backtracking with generalized
lookahead guards using the special nonterminal forms "[see X]" (the
input stream lookahead from here *must* be parseable as an [X]) and
"[not X]" (the input stream lookahead from here must *not* be parseable
as an [X]). ("[X]" is TXL notation for the nonterminal "<X>".)


For example, the following nonterminal definition resolves the local
ambiguity between assignment statements and procedure calls using a
lookahead to see that we don't have a parseable assignment:


define procedure_call
        [not assignment] [id] [opt arguments]
end define


Lookaheads can be arbitrary nonterminals since full backtracking is
used.


Jim

Post a followup to this message

Return to the comp.compilers page.
Search the comp.compilers archives again.