boolean

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

NAME
       boolean - Boolean support for Perl

VERSION
       This document describes boolean version 0.46.

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);

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
       encodedecoderoundtrip 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"

DEPRECATIONS
       This module offered an export tag, "-truth", that overrides the Perl
       interpreter's internal values for true and false. This has been found
       to corrupt the interpreter in some circumstances. Also, these overrides
       will no longer be possible as of Perl 5.22. Therefore, the "-truth"
       import tag is deprecated.

JSON SUPPORT
       JSON::MaybeXS (or less preferably JSON.pm ) will encode Perl data with
       boolean.pm values correctly if you use the "convert_blessed" option:

           use JSON::MaybeXS;
           use boolean -truth;
           my $json = JSON::MaybeXS->new->convert_blessed;
           say $json->encode({false => (0 == 1)});     # Says: '{"false":false}',

AUTHOR
       Ingy dot Net <ingy@cpan.org>

COPYRIGHT AND LICENSE
       Copyright 2007-2016. Ingy dot 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 v5.22.2                      2016-07-09                      boolean(3pm)