Update: I am so sorry. I didn't read your post thoroughly enough. This is actually an infix-expression parser. I posted code that solves your problem in a reply to this post. -- Steffen

The following code should solve your problem including operator precedence (and > or > == > !).

Note, however, that it will be very slow when dealing with long strings. 

use strict;
use warnings;
use Data::Dumper;
use Parse::RecDescent;

my $grammar = <<'GRAMMAR';

boolean_expr:   and_expr                        { $item[1] }
              | terminal                        { $item[1] }
              | <error>

and_expr:       <leftop: or_expr 'and' or_expr>
                {
                        my $ary = $item[1];
                        my $return = $ary->[0];
                        foreach (@{$ary}[1..$#$ary]) {
                                $return = ['and', $return, $_];
                        }
                        $return;
                }

or_expr:        <leftop: eq_expr 'or' eq_expr>
                {
                        my $ary = $item[1];
                        my $return = $ary->[0];
                        foreach (@{$ary}[1..$#$ary]) {
                                $return = ['or', $return, $_];
                        }
                        $return;
                }

eq_expr:        <leftop: unary_expr '==' unary_expr>
                {
                        my $ary = $item[1];
                        my $return = $ary->[0];
                        foreach (@{$ary}[1..$#$ary]) {
                                $return = ['==', $return, $_];
                        }
                        $return;
                }

unary_expr:     '!' term                        { ['!', $item[2]] }
              | term                            { $item[1] }


term:           '(' boolean_expr ')'            { $item[2] }
              | terminal                        { $item[1] }

terminal:       /\w+/                           { $item[1] }

GRAMMAR

my $parser = Parse::RecDescent->new($grammar);

while (<STDIN>) {
        chomp;
        my $parsed;
        $parsed = $parser->boolean_expr($_);
        next unless defined $parsed;
        print Dumper $parsed;
}

[download]

For a more involved example of a Parse::RecDescent grammar for parsing similar expressions, have a look at the Math::Symbolic::Parser module (algebraic expressions in that case).

Steffen

In reply to Re: prefix notation in an array by tsee
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.