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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Why constant components are not permitted ?
Date: Fri, 25 Nov 2011 18:41:36 +0100
Organization: Tidorum Ltd
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Date: 2011-11-25T18:41:36+01:00
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On 11-11-25 11:06 , AdaMagica wrote:
> 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;

The original poster specified the constant value in the declaration of 
the record *type*, not separately for each record *object*. This is what 
I do not understand: what is the use of a value that is the same for all 
objects in which it can appear?

The "type constants" that Ada now provides are the attributes of a type 
(tag, size, and so on), as Ludovic pointed out.

I understand that some would like to have a "write once" kind of record 
component that can be given a value once, when a record object is 
created, and cannot be changed afterwards. Discriminants are like that 
in Ada, but cannot be of arbitrary type.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .