(I am using terms "parser", "tokenizer / lexer", "abstract syntax tree (AST)" in a compiler context.)

I was pointed to the YAPE::Regex module "Yet Another Parser/Extractor for Regular Expressions". From the documentation and my experiments in the debugger, I believe it to be only a lexer, not a proper parser. As far as I can tell, it breaks down the text of a RE into strings of characters with particular meanings (tokens), but it doesn't assemble those meanings into a hierarchy (abstract syntax tree).

For a quick look at the AST of a RE, you can see the indented text in "Debugging regular expressions" of man perldebguts or 

perl
-Mre=debug -e '$re =  qr/^a(b(cd?)?)?/;'

[download]
.

To do one of the transformations that many of us have thought up, I should be operating on the AST, not just on the individual tokens. Also, I would have to break each EXACT node into a sequence of single-character EXACT nodes.

In reply to Re: Re: Matching against a partially known string by wonkozen
in thread Matching against a partially known string by Anonymous Monk

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!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • 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, details, 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, summary, 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.