NAME
boolean - Boolean support for Perl
VERSION
This document describes boolean version 0.46.
SYNOPSIS
and:
$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
$scalar
is true, it returnsboolean::true
, otherwise it returnsboolean::false
. isTrue($scalar)
-
Returns
boolean::true
if the scalar passed to it is theboolean::true
object. Returnsboolean::false
otherwise. isFalse($scalar)
-
Returns
boolean::true
if the scalar passed to it is theboolean::false
object. Returnsboolean::false
otherwise. isBoolean($scalar)
-
Returns
boolean::true
if the scalar passed to it is theboolean::true
orboolean::false
object. Returnsboolean::false
otherwise.
METHODS
Since true and false return objects, you can call methods on them.
USE OPTIONS
By default this module exports the true
, false
and boolean
functions.
The module also defines these export tags:
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@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.