A.19 The Package Locales
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A
locale identifies a geopolitical place or
region and its associated language, which can be used to determine other
internationalization-related characteristics.
Static Semantics
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The library package Locales has the following declaration:
package Ada.Locales
is
pragma Preelaborate(Locales);
pragma Remote_Types(Locales);
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type Language_Code
is new String (1 .. 3)
with Dynamic_Predicate =>
(
for all E
of Language_Code => E
in 'a' .. 'z');
type Country_Code
is new String (1 .. 2)
with Dynamic_Predicate =>
(
for all E
of Country_Code => E
in 'A' .. 'Z');
Discussion: {
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These types are derived from type String so that they can easily be converted
to or from type String. That's important if one of these values needs
to be input or displayed (via Text_IO, perhaps). We use the predicate
to ensure that only possible component values are used. Ada does not
allow converting between unrelated types with components that don't statically
match, so we cannot declare new types with constrained components if
we want conversions to or from type String.
Language_Unknown :
constant Language_Code := "und";
Country_Unknown :
constant Country_Code := "ZZ";
function Language
return Language_Code;
function Country
return Country_Code;
end Ada.Locales;
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The
active locale is the
locale associated with the partition of the current task.
Implementation Note: {
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Some environments define both a system locale and the locale of the current
user. For such environments, the active locale is that of current user
if any; otherwise (as in a partition running on a server without a user),
the system locale should be used.
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Language_Code is a lower-case string representation of an ISO 639-3 alpha-3
code that identifies a language.
Discussion: Some common language codes
are: "eng" – English; "fra" – French;
"deu" – German; "zho" – Chinese. These
are the same codes as used by POSIX systems. We considered including
constants for the most common languages, but that was rejected as the
likely source of continual arguments about the constant names and which
languages are important enough to include.
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Country_Code is an upper-case string representation of an ISO 3166-1
alpha-2 code that identifies a country.
Discussion: Some common country codes
are: "CA" – Canada; "FR" – France; "DE"
– Germany; "IT" – Italy; "ES" –
Spain; "GB" – United Kingdom; "US" –
United States. These are the same codes as used by POSIX systems. We
didn't include any country constants for the same reasons that we didn't
include any language constants.
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Function Language returns the code of the language associated with the
active locale. If the Language_Code associated with the active locale
cannot be determined from the environment, then Language returns Language_Unknown.
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Function Country returns the code of the country associated with the
active locale. If the Country_Code associated with the active locale
cannot be determined from the environment, then Country returns Country_Unknown.
Extensions to Ada 2005
Inconsistencies With Ada 2012
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Corrigendum: Types Language_Code and Country_Code
are defined with predicates rather than constrained components so that
they can be converted to/from type String. This changes the exception
raised from Constraint_Error to Assertion_Error if an assignment is attempted
with an incorrect value. This could only matter if there is a handler
specifically for Constraint_Error surrounding this assignment; as this
exception raise is certainly caused by a bug (why would anyone want to
use invalid language or country codes?), such a handler seems very unlikely.
(In addition, this is a new Ada 2012 package, so there is not likely
to be a lot of code using it.)
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
