Null Language-Independent Type for YAML™ Version 1.1

Working Draft 2005-01-18

Oren Ben-Kiki

<oren@ben-kiki.org>

Clark Evans

<cce+yaml@clarkevans.com>

Brian Ingerson

<ingy@ttul.org>

This document may be freely copied provided it is not modified.

Status

This specification is a draft reflecting consensus reached by members of the yaml-core mailing list. Any questions regarding this draft should be raised on this list.

URI:

tag:yaml.org,2002:null

Shorthand:

!!null

Kind:

Scalar.

Canonical:

~

Regexp:

 ~ # (canonical)
|null|Null|NULL # (English)
| # (Empty)

Definition:

Devoid of value.

A null value is used to indicate the lack of a value. This is typically converted into any native null-like value (e.g., undef in Perl, None in Python). Note that a null is different from an empty string and that a mapping entry with some key and a null value is valid and different from not having that key in the mapping.

Example 1. !!null Examples

# A document may be null.
---
---
# This mapping has four keys,
# one has a value.
empty:
canonical: ~
english: null
~: null key
---
# This sequence has five
# entries, two have values.
sparse:
  - ~
  - 2nd entry
  -
  - 4th entry
  - Null