boolean - Boolean support for Perl
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';
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.
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.
This module defines the following functions:
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.
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.
Casts the scalar value to a boolean value. If $scalar is true, it returns boolean::true, otherwise it returns boolean::false.
Returns boolean::true if the scalar passed to it is the boolean::true object. Returns boolean::false otherwise.
Returns boolean::true if the scalar passed to it is the boolean::false object. Returns boolean::false otherwise.
Returns boolean::true if the scalar passed to it is the boolean::true or boolean::false object. Returns boolean::false otherwise.
Since true and false return objects, you can call methods on them.
Same as isTrue($boolean).
Same as isFalse($boolean).
By default this module exports the true, false and boolean functions.
The module also defines these export tags:
Exports true, false, boolean, isTrue, isFalse, isBoolean
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.pm will encode Perl data with boolean.pm values correctly if you use the convert_blessed option:
use JSON;
use boolean -truth;
my $json = JSON->new->convert_blessed;
say $json->encode({false => (0 == 1)}); # Says: '{"false":false}',
Ingy döt Net <ingy@cpan.org>
Copyright (c) 2007, 2008, 2010, 2011, 2013. Ingy döt Net.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
