boolean(3pm)                                            User Contributed Perl Documentation                                           boolean(3pm)

NAME

       boolean - Boolean support for Perl

SYNOPSIS

           use boolean;

           do &always if true;
           do &never if false;

           do &maybe if boolean($value)->isTrue;

       and:

           use boolean ':all';

           $guess = int(rand(2)) % 2 ? true : false;

           do &something if isTrue($guess);
           do &something_else if isFalse($guess);

       and:

           use boolean -truth;

           die unless ref(42 == 42) eq 'boolean';
           die unless ("foo" =~ /bar/) eq '0';

DESCRIPTION

       Most programming languages have a native "Boolean" data type.  Perl does not.

       Perl has a simple and well known Truth System. The following scalar values are false:

           $false1 = undef;
           $false2 = 0;
           $false3 = 0.0;
           $false4 = '';
           $false5 = '0';

       Every other scalar value is true.

       This module provides basic Boolean support, by defining two special objects: "true" and "false".

RATIONALE

       When sharing data between programming languages, it is important to support the same group of basic types. In Perlish programming
       languages, these types include: Hash, Array, String, Number, Null and Boolean. Perl lacks native Boolean support.

       Data interchange modules like YAML and JSON can now "use boolean" to encode/decode/roundtrip Boolean values.

FUNCTIONS

       This module defines the following functions:

       true
           This function returns a scalar value which will evaluate to true. The value is a singleton object, meaning there is only one "true"
           value in a Perl process at any time. You can check to see whether the value is the "true" object with the isTrue function described
           below.

       false
           This function returns a scalar value which will evaluate to false. The value is a singleton object, meaning there is only one "false"
           value in a Perl process at any time. You can check to see whether the value is the "false" object with the isFalse function described
           below.

       boolean($scalar)
           Casts the scalar value to a boolean value. If $scalar is true, it returns "boolean::true", otherwise it returns "boolean::false".

       isTrue($scalar)
           Returns "boolean::true" if the scalar passed to it is the "boolean::true" object. Returns "boolean::false" otherwise.

       isFalse($scalar)
           Returns "boolean::true" if the scalar passed to it is the "boolean::false" object. Returns "boolean::false" otherwise.

       isBoolean($scalar)
           Returns "boolean::true" if the scalar passed to it is the "boolean::true" or "boolean::false" object. Returns "boolean::false"
           otherwise.

METHODS

       Since true and false return objects, you can call methods on them.

       $boolean->isTrue
           Same as isTrue($boolean).

       $boolean->isFalse
           Same as isFalse($boolean).

USE OPTIONS

       By default this module exports the "true", "false" and "boolean" functions.

       The module also defines these export tags:

       :all
           Exports "true", "false", "boolean", "isTrue", "isFalse", "isBoolean"

   -truth
       You can specify the "-truth" option to override truth operators to return "boolean" values.

           use boolean -truth;
           print ref("hello" eq "world"), "
";

       Prints:

           boolean

       "-truth" can be used with the other import options.

AUTHOR

       Ingy doet Net <ingy@cpan.org>

COPYRIGHT

       Copyright (c) 2007, 2008, 2010, 2011. Ingy doet Net.

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

       See http://www.perl.com/perl/misc/Artistic.html

perl v5.12.4                                                        2011-09-12                                                        boolean(3pm)