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 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

-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.

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@cpan.org>

COPYRIGHT

Copyright 2007, 2008, 2010, 2011, 2013, 2014. 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