Re: ADA Objects Help!

[dobrien@seas.gwu.edu (David O'Brien)]

Ed Osinski (osinski@hellgate.cs.nyu.edu) wrote:
: |> >
: |> >C++ has two procedure calling syntaxes.  It is possible to write either
: |> >   display(myptr);
: |> >or
: |> >   myptr->display();
: |>  
: |> >These both call a procedure, passing the value myptr as the argument.
: |> >In contrast, Ada provides only a single procedure call syntax.
: |> >
: |> >When you declare a procedure in C++ you specify which syntax will be
: |> >used to call the procedure.
: |>  
: |> Again, there is much more to it than just the syntax.  One is a member
: |> function, the other is a plain-old function.  Big, big, difference. 

: Sure, but why does the caller need to know which one is used?

Point is, you don't.  The first form really won't exist in OOP.  Problem
is both Ada and C++ are hybrid OO languages.  So we keep thinking in
our old imperative way, while trying to implement in an OOP way.

I'm kinda surprised to see this actually since in Ada it is common to
see "text_io.put_line( .... );".  So why does the programmer have to
know which package ``put_line'' belongs to?  Yes we could just "use" the
package, but then you've never worked on a DoD contract that forbidden
the use of "use" statements.  Actually, it is this syntax and scoping
rules that gave Ada83 a partially OO feel.  Plus, it is
self-documenting code.  :-)))

: for calling them.  In fact, even C++ does let you use the non-member syntax 
: for *some* members.  They're called operators.  When you see

: 	a + b

Same syntax as Ada83.  You could use package_name.op( a, b );

-- David O'Brien	(dobrien@seas.gwu.edu)