Beefy Boxes and Bandwidth Generously Provided by pair Networks
Syntactic Confectionery Delight
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
ikegami++ .. I recently tried to get a sane parse tree from a grammar which (like your example scenario) was the result of left-recursion elimination on left-associative grammar rules. I found it to be highly nontrivial.

I was at least aware of the first two approaches you presented (though it would have taken me a long time to get approach #3a working), but it had not occured to me to use an accumulation paradigm like you do in #3c. This is a standard trick in making recursive functions tail-recursive (pass forward the intermediate results as an argument, instead of passing back the intermediate results as a return value).

I probably wouldn't have thought to apply this trick to parsing, though. If you're a theorist like me and view parsing through the lens of formal languages, then passing information from parent rule to child rule is not a natural approach. Good thing there are still practitioners out there ;)

blokhead


In reply to Re: Operator Associativity and Eliminating Left-Recursion in Parse::RecDescent by blokhead
in thread Operator Associativity and Eliminating Left-Recursion in Parse::RecDescent by ikegami

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others pondering the Monastery: (9)
    As of 2015-07-02 02:20 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









      Results (25 votes), past polls