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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 AT 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)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
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