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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Why constant components are not permitted ?
Date: Sat, 26 Nov 2011 11:59:26 +0100
Organization: cbb software GmbH
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Date: 2011-11-26T11:59:26+01:00
List-Id: <comp.lang.ada>

On Sat, 26 Nov 2011 11:22:35 +0100, Pascal Obry wrote:

> Le 25/11/2011 11:06, AdaMagica a �crit :
>> Useful applications for constant components could be (this is what you
>> can have in C++):
>> 
>> record  -- *not* Ada
>>   Name: constant String   := "James Bond";
>>   Id  : constant Positive := 007;  -- e.g employee number of a company
>>   other variable components
>> end record;
>> 
>> In Ada, you hide the components (private record), define a constructor
>> function providing the values for the constant items and provide only
>> read operations for them.
> 
> But why on earth do you want a field in a record with the same value for
> all objects of this type?

   record -- This is not Ada!
      Name : constant Unbounded_String := Read (File);

Of course it should be possible to initialize constant fields upon object
construction:

   record -- This is not Ada!
      Name : constant Unbounded_String;  -- Deferred until construction

Also don't forget constant views of fields which are privately
non-constant.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de