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From: aratel@total.net (Andre Ratel)
Subject: Re: Ada vs Delphi?
Date: 1999/08/11
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Newsgroups: comp.lang.ada
Date: 1999-08-11T00:00:00+00:00
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-= Mixing types =-------------------------

On Mon, 09 Aug 1999 02:51:34 GMT, Robert Dewar
<robert_dewar@my-deja.com> wrote:

> What you can do in Pascal, which you cannot do in
>Ada, is to freely mix "different" integer types. I put the
>"different" in quotes since really there is only one integer
>type in Pascal (at least by Ada standards).

I'm not sure I fully understand. Let's say n1 and n2 are known
to be non-negative integers (called cardinals in Delphi) but their
difference  might be positive or negative. In Delphi, I would then
declare these variables as

  type
    n1, n2: cardinal; 
    N21, N12: integer; 

and I could have something like

  begin
    n1:= 0;
    n2:= 8;
    N21:= n2 - n1;
    Writeln(IntToStr(N21));
    N12:= n1 - n2;
    Writeln(IntToStr(N12));
  end;     

This seems OK with me and, with range checking off, would give the
right answers (8 and -8). On the other hand, a statement like
    Writeln(IntToStr(n1 - n2));
would give  4294967288.

Now, with the above definitions of variables, a statement like
    N21:= n2 - n1;
would not be valid with Ada?

rem: If, in the above program, I add the compiler directive
       {$RANGECHECK ON}
     calculating N12 leads to a range check error (although
     N12 has been declared as an integer).

-= Absence of standards =--------------------------

>Pascal is really not "truely" well defined. FOr one thing, it
>is a mess that the ANSI standards and ISO standards are
>different (I assume this is still the case, if this abominable
>state of affairs has been fixed, let me know).

I often read this as one of the main reasons for the demise
of Pascal and its replacement by C. (As for the other reason,
I would suggest that C simply rides on the popularity of Unix.)

>Second, almost no Pascal compilers implement exactly the
>standard and nothing more. One of the VERY important aspects
>of Ada is that a standard Ada compiler is not permitted any
>extensions over what is in the standard, so in practice it is
>far easier to write portable Ada programmers, and there is
>one source of the standard semantics.

This is certainly one major advantage of Ada over Delphi.

	Andre