Rationale for Ada 2012

John Barnes
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7.4 Locale

When writing portable software it is often necessary to know the locality in which the software is to be run. Two key items are the country and the language (human language that is, not programming language).
To enable this to be done, Ada 2012 includes the following package
package Ada.Locales is
   pragma Preelaborate(Locales);
   pragma Remote_Types(Locales);}
   type Language_Code is array (1 .. 3) of Character range 'a' .. 'z';
   type Country_Code is array (1 .. 2) of Character range 'A' .. 'Z';
   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;
The various country codes and language codes are defined in ISO/IEC 3166-1:2006 and ISO/IEC 639-3:2007 respectively.
Knowledge of the locale is important for writing programs where the convention for certain information varies. Thus in giving a date we might want to add the name of the day of the week and clearly in order to do this we need to know what language to use. An earlier (really grotesque) attempt at providing this information introduced a host of packages addressing many issues. However, it was decided that for simplicity and indeed reliability all that is really needed is to know the language to use and the country.
Canada is interesting in that it has just one country code ("CA") but two language codes ("eng" and "fra"). In Quebec, a decimal value for a million dollars and one cent is written as $1.000.000,01 whereas in English language parts it is written as $1,000,000.01 with the comma and stop interchanged.
Sometimes, several locales might be available on a target. Some environments define a system locale and a locale for the current user. In the case of an Ada program the active locale is the one associated with the partition of the current task.
Finally, note that subsequent to ISO standardization, some serious difficulty was found in the practical use of the types Language_Code and Country_Code. Accordingly, they have been changed as described in Section 9.5 of the Epilogue.

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