Re: on OO differnces between Ada95 and C++

[Jerome Desquilbet <jDesquilbet@Rational.COM>]

Nasser,

You have pointed out one of the main differences between Ada and C
compilation models (and as far as the compilation model is concerned,
Ada 95 is not different from Ada 83, and C++ is not different from C).


- The C/C++ compilation paradigm is _independent_ compilation.

- The Ada 83/95 compilation paradigm is _separate_ compilation.


It has nothing to do with the OO features of the two languages.


The comparison between these two compilation models would take some
place, but here a list of some comments about the C/C++ compilation
model:

- .C files may be compiled in any order

- .h files are not compiled

- there is no way to avoid use of the preprocessor (at least for
#include)

- there is no way to oblige the programmer to write all the #include
directives: he may take advantage of some "hidden" includes (nested at
more than one level)

- the really compiled file (the compilation unit) is the result of the
preprocessing phase

- conventions like

  #ifndef X_H_
  #define X_H_
  ...
  #endif

  in headers to prevent multi-inclusion are only conventions, they are
not part of the language

- you may have several different definitions for the same class in the
same program, as long as they are never compiled together in the same
compilation unit; example:

#define private public // *** BERK! ***
#include "...h"        // second definition for the same class
#undef private

  Jerome.