NAME

boolean - Boolean support for Perl

SYNOPSIS

    use boolean;

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

and:

    use boolean ':all';

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

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

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.

IMPLEMENTATION NOTE

Version 0.20 is a complete rewrite from version 0.12. The old version used XS and had some fundamental flaws. The new version is pure Perl and is more correct. The new version depends on overload.pm to make the true and false objects return 1 and 0 respectively.

The "null" support found in 0.12 was also removed as superfluous.

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 should 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 should 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.
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.

EXPORTABLES

By default this module exports the true and false functions.

The module also defines these export tags:

:all: Exports true, false, isTrue, isFalse, isBoolean
:test: Exports isTrue, isFalse, isBoolean

AUTHOR

Ingy dÃ¶t Net <ingy@cpan.org>

COPYRIGHT

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