Expand description

Language Identifier and Locale contains a set of subtags which represent different fields of the structure.

  • Language is the only mandatory field, which when empty, takes the value und.
  • Script is an optional field representing the written script used by the locale.
  • Region is the region used by the locale.
  • Variants is a list of optional Variant subtags containing information about the variant adjustments used by the locale.

Subtags can be used in isolation, and all basic operations such as parsing, syntax canonicalization and serialization are supported on each individual subtag, but most commonly they are used to construct a LanguageIdentifier instance.

Variants is a special structure which contains a list of Variant subtags. It is wrapped around to allow for sorting and deduplication of variants, which is one of the required steps of language identifier and locale syntax canonicalization.


use icu::locid::subtags::{Language, Region, Script, Variant};

let language: Language =
    "en".parse().expect("Failed to parse a language subtag.");
let script: Script =
    "arab".parse().expect("Failed to parse a script subtag.");
let region: Region =
    "cn".parse().expect("Failed to parse a region subtag.");
let variant: Variant =
    "MacOS".parse().expect("Failed to parse a variant subtag.");

assert_eq!(language.as_str(), "en");
assert_eq!(script.as_str(), "Arab");
assert_eq!(region.as_str(), "CN");
assert_eq!(variant.as_str(), "macos");

Notice: The subtags are canonicalized on parsing. That means that all operations work on a canonicalized version of the subtag and serialization is very cheap.


A language subtag (examples: "en", "csb", "zh", "und", etc.)

A region subtag (examples: "US", "CN", "AR" etc.)

A script subtag (examples: "Latn", "Arab", etc.)

A variant subtag (examples: "macos", "posix", "1996" etc.)

A list of variants (examples: ["macos", "posix"], etc.)