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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Is this expected behavior or not
Date: Thu, 18 Apr 2013 21:16:58 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2013-04-18T21:16:58-05:00
List-Id: <comp.lang.ada>

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:qtagj9gwjjxn$.ljj8purwznkr.dlg@40tude.net...
...
> Your concept simply does not hold. There are simple indisputable facts:
>
> 1. The representation of string object is irrelevant to what string is.

This is clearly false, so it's pretty clear why you end up with bizarre 
conclusions.

Specifically, the number of characters that a string object can hold (and 
whether that number can change, and by how much) is *indisputably* a 
critical part of string object semantics. This is so tightly interwined by 
the underlying representation (when you chose one, you pretty much chose the 
other) that practically it is inseparable.

It's certainly true that you can have an abstract string interface that 
doesn't expose the representation -- that's the idea behind my 
Root_String'Class proposal -- and that's useful in a limited set of 
circumstances (mostly in read-only situations, which is the majority of 
string operations anyway). But it does not describe the complete semantics 
of a string object, nor could it.

> 2. It is impossible to have one implementation suitable for all string
> objects and all application domains that use strings, e.g. DNA sequencing,
> pattern matching, text processing, compiler construction etc.

Of course. So what? That's why we want a variety of string types for 
different jobs. That gives no reason why anyone should be mixing them! What 
do you get when you concatenate a DNA sequence and an Ada identifier? A bug! 
:-)

                                    Randy.