NAME

       Badger::Logic - parse and evaluate simple logical expressions

SYNOPSIS

           use Badger::Logic 'Logic';

           my $logic  = Logic('animal and (eats_nuts or eats_berries)');
           my $values = {
               animal    => 1,
               eats_nuts => 1,
           }

           if ($logic->test($values)) {
               print "This is an animal that eats nuts or berries\n";
           }

DESCRIPTION

       This module implements a simple parser and evaluator for boolean logic expressions.  It
       evolved from a piece of code that I originally wrote to handle role-based authentication
       in web applications.

EXPORTABLE SUBROUTINES

   LOGIC
       This is a shortcut alias to "Badger::Logic".

           use Badger::Logic 'LOGIC';

           my $logic = LOGIC->new($expr);      # same as Badger::Logic->new($expr);

   Logic()
       This subroutine returns the name of the "Badger::Logic" class when called without
       arguments. Thus it can be used as an alias for "Badger::Logic" as per LOGIC.

           use Badger::Logic 'Logic';

           my $logic = Logic->new($expr);      # same as Badger::Logic->new($expr);

       When called with arguments, it creates a new "Badger::Logic" object.

           my $logic = Logic($expr);           # same as Badger::Logic->new($expr);

METHODS

   new($expr)
       Constructor method to create a new "Badger::Logic" object from an expression.

           my $logic = Badger::Logic->new('animal and (cat or dog)');

   evaluate($values) / test($values)
       Method to evaluate the expression.  A reference to a hash array should be passed
       containing the values that the expression can test.

           my $values = {
               animal => 1,
               cat    => 1,
           };

           if ($logic->evaluate($values)) {
               print "This animal is a cat or a dog\n";
           }

   tree()
       Returns a reference to the root of a tree of "Badger::Logic::Node" objects that represent
       the parsed expression.

   text()
       Returns a text representation of the logic expression.

INTERNAL METHODS

   parse($text)
       Main method to parse a logical expression.  This calls parse_expr() and then checks that
       all of the text has been successfully parsed.  It returns a reference to a
       "Badger::Logic::Node" object.

   parse_expr($text)
       Method to parse a binary expression.

   parse_unary($text)
       Method to parse a unary expression.

   parse_term($text)
       Method to parse a single term in a logical expression.

AUTHOR

       Andy Wardley <http://wardley.org>

COPYRIGHT

       Copyright (C) 2007-2009 Andy Wardley.  All Rights Reserved.

       This module is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.