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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Ada and Java. different behaviour. casting long to int problem.
Date: 1999/06/18
Message-ID: <m3bteenjx6.fsf@mheaney.ni.net>#1/1
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NNTP-Posting-Date: Thu, 17 Jun 1999 22:39:57 PDT
Newsgroups: comp.lang.ada,comp.lang.java.programmer
Date: 1999-06-18T00:00:00+00:00
List-Id: <comp.lang.ada>

On 18 Jun 1999 11:15, dale@cs.rmit.edu.au (Dale Stanbrough) wrote:

> ...but i think that Java is easier to read in some circumstances. You don't
> end up having the code cluttered up with ".all", "'access" and "access".

It depends on your style of programming.  Access parameters were added
to the language specifically to avoid having to explicitly dereference
access objects:

  declare
    Matt : Man_Access := New_Man;
  begin
    Shave (Matt);
    ...
  end;


where

  procedure Shave (Man : access Man_Type);


One thing Java does give you is automatic garbage collection, but we can
emulate that easily enough:

  type Man_Handle is private;  

  function "+" (Handle : Man_Handle) return Man_Access;


  function New_Man return Man_Handle;

  declare
    Matt : Man_Handle := New_Man;
  begin
    Shave (+Matt);
    ...
  end;


So you see, explicit dereferencing and 'Access are often unnecessary.  The
time when need to do that sort of thing is when you're programming close
to the machine (which is entirely appropriate).

Browse the Ada95 design patterns archive for more examples of access
parameter and garbage collection idioms.

<http://www.acm.org/archives/patterns.html>


    
> I also like Java's interfaces, a feature I'm not sure how Ada can replicate.

You can do something like that using access discriminants.  See the
observer series (in the patterns archive) for lots o' examples.