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From: Jacob Sparre Andersen <sparre@nbi.dk>
Newsgroups: comp.lang.ada
Subject: Re: Range types
Date: Mon, 22 Oct 2007 09:23:01 +0200
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Date: 2007-10-22T09:23:01+02:00
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Christos Chryssochoidis wrote:

> I would like to define a subtype of Wide_Character for a program
> that processes (unicode) text. This type would represent the Greek
> letters.

This sounds like what enumerated types are for.  You could do it like
this:

   type Faroese_Letter is ('a', 'A', 'b', 'B', 'd', 'D', '�', '�',
                           'e', 'E', [...],
                           'y', 'Y', '�', '�', '�', '�', '�', '�');
   -- optional representation clause

   function To_Wide_Wide_Character (Item : in Faroese_Letter)
     return Wide_Wide_Character;

   function To_Faroese_Letter (Item : in Wide_Wide_Character)
     return Faroese_Letter;

The conversion functions could make use of representation clauses,
"Image" and "Value" functions, or tables.

> Greek letters in Unicode, with all their diacritics, are
> located in two separate ranges: 0370 - 03D7 and 1F00 - 1FFF. That's
> 360 characters to write in an enumeration... Since gaps are not
> allowed in ranges, I 'm thinking instead of defining such a type, to
> define a function that would accept a Wide_Character as argument and
> return a boolean value indicating whether the given Wide_Character
> falls in the ranges of the Greek characters.

This could be done very simply using Ada.Strings.Maps.

How you should do it depends strongly on what you actually need your
Greek_Letter type for.

Greetings,

Jacob
-- 
"Only Hogwarts students really need spellcheckers"
                                -- An anonymous RISKS reader