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boolean.3pm

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 do.t Net <ingy@cpan.org>

COPYRIGHT

Copyright (c) 2007, 2008. Ingy do.t 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