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"), "\n";

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