phpman > man > 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 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"

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 döt Net <ingy AT cpan.org>

COPYRIGHT AND LICENSE
    Copyright 2007-2016. Ingy döt 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>