In this section we explain how we specify locales in stringi. Locale is a fundamental concept in ICU. It identifies a specific user community, i.e., a group of users who have similar culture and language expectations for human-computer interaction.
ICU services are parametrized by locale,
to deliver culturally correct results.
Locales are identified by character strings
of the form
Language_Country code, or
code, e.g., 'en_US'.
Language code uses the ISO-639-1 standard,
e.g., 'en' stands for English, 'pl' -- Polish, 'fr' -- French,
and 'de' for German.
Country is a two-letter code following the ISO-3166 standard.
This is to reflect different language conventions within the same language,
for example in US-English ('en_US') and Australian-English ('en_AU').
Differences may also appear in language conventions used within
the same country. For example, the Euro currency may be used in several European
countries while the individual country's currency is still in circulation.
In such a case, ICU
Variant '_EURO' could be used for selecting
locales that support the Euro currency.
The final (optional) element of a locale is a list of
keywords together with their values. Keywords must be unique.
Their order is not significant. Unknown keywords are ignored.
The handling of keywords depends on the specific services that
utilize them. Currently, the following keywords are recognized:
calendar=islamic-civil is a valid
French locale specifier together with keyword arguments. For
more information, refer to the ICU user guide.
For a list of locales that are recognized by ICU,
Each locale-sensitive function in stringi
selects the current default locale if an empty string or
is provided as its
locale argument. Default locales are available
to all the functions:
they are initially set to be the system locale on that platform,
and may be changed with
for example, if automatic detection fails to recognize
your locale properly.
It is suggested that your program should avoid changing
the default locale.
All locale-sensitive functions may request
any desired locale per-call (by specifying the
i.e., without referencing to the default locale.
During many tests, however, we did not observe any improper
behavior of stringi while using a modified default locale.
One of many examples of locale-dependent services is the Collator, which
performs a locale-aware string comparison. It is used for string comparing,
ordering, sorting, and searching. See
for the description on how to tune its settings, and its
argument in particular.
Other locale-sensitive functions include, e.g.,
stri_trans_tolower (that does character case mapping).
Because a locale is just an identifier of a region, no validity check is performed when you specify a Locale. ICU is implemented as a set of services. If you want to verify whether particular resources are available in the locale you asked for, you must query those resources. Note: when you ask for a resource for a particular locale, you get back the best available match, not necessarily precisely the one you requested.
Locale -- ICU User Guide, https://unicode-org.github.io/icu/userguide/locale/
ISO 639: Language Codes, https://www.iso.org/iso-639-language-codes.html
ISO 3166: Country Codes, https://www.iso.org/iso-3166-country-codes.html
The official online manual of stringi at https://stringi.gagolewski.com/