Problems like this involve two parts: parsing and syntax-directed translation. So the first step is to create a grammar for your infix expression: 
# infix operators: ==, or, and
# grouping: ()
# terminals : \w+
#
# term := (expr)
#         | \w+ 
# expr := term /and/ term
#         | term /or/ term
#         | term /==/ term

[download]
Parsing expressions usuing this grammar will generate a parse tree. Then you can walk the parse tree to create the prefix notation. In our case, the grammar is so simple, we can translate as we go along: 
# infix operators: ==, or, and
# grouping: ()
# terminals : \w+
#
# term := (expr)             {print '[' .  $expr . ']'}
#         | \w+              {print $word}
# expr := term /and/ term    {print 'and,' . $term1 . ',' . $term2}
#         | term /or/ term   {print 'or,' . $term1 . ',' . $term2}
#         | term /==/ term   {print '==,' . $term1 . ',' . $term2}

[download]
The bits in {} are called actions and you can take them as soon as you satisfy the given parse rule.

Given the grammar and actions, your task is (you didn't think I would take all the fun out of it, did you?) to create a recursive descent program implementing this grammar. The grammar is simple enough that you could hand-roll your own. Or you could use Parse::RecDescent to automatically generate a program from your grammar (you may have to tweak the grammar to satisfy P::RD's grammar format).

Have fun!

-Mark

In reply to Re: prefix notation in an array by kvale
in thread prefix notation in an array by amw1

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.