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From: Cesar Rabak <csrabak@yahoo.com.br>
Newsgroups: comp.lang.eiffel,comp.lang.ada
Subject: Re: Alternatives to C: ObjectPascal, Eiffel, Ada or Modula-3?
Date: Tue, 21 Jul 2009 12:02:08 -0300
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Date: 2009-07-21T12:02:08-03:00
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Jean-Pierre Rosen escreveu:
> Cesar Rabak a �crit :
>> Ludovic Brenta escreveu:
[snipped]
>> More or less. It has all the operations of the derived type, uses the
>> same representation on the machine.  The incompatibility is syntactic no
>> in its essence.
>>
> Here is the crux of the misunderstanding: sure, at /machine/ level they
> are the same, but in the /problem domain/ they are different. The big
> difference between Ada an other languages is that types (even elementary
> ones) reflect the problem domain, not machine types.

Yes but the crux is another: the four 'new types' suggested for solution 
to a problem shown by B. Meyers in Ada language for the need of 
different function signatures *do not* reflect the problem domain: for 
the later all the numbers are just this _numbers�_.  The Ada 
implementation in order to be able to have two different 'constructors' 
for the new type Point (this indeed a *new* type) created through its 
mechanisms subtypes, which only send the trash over the wall.  All this 
discussion about avoiding programmer errors can be attained instead of 
creating four nicknames for Float to allow:

procedure makePointXY(X : Float; Y : Float) is
    begin
       null; --Whatever.
    end;

procedure makePoint_R_Theta(R : Float; Theta : Float) is
    begin
       null; --Whatever.
    end;

Do you agree the programmer will find the mistake easily as well?

--
Cesar Rabak

[1] Specializations of the concept for say a screen where coordinates 
are integers and limited to screeen area, for example are not being 
discussed here, as are not the kernel of Meyer's critique.