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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: not null access procedure
Newsgroups: comp.lang.ada
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Organization: cbb software GmbH
References: <AJs6f.26037$Pe2.505823@twister2.libero.it>
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Date: Wed, 2 Nov 2005 09:10:42 +0100
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Date: 2005-11-02T09:08:49+01:00
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On 01 Nov 2005 20:07:47 -0500, Robert A Duff wrote:

> Anonymous Coward <bogus_addy@bogus_domain.net> writes:
> 
>> I noticed some syntax in the package specification of that link above,
>> which is unfamiliar to me:
>> 
>>    procedure Update_Element
>>      (Container : in out Vector;
>>       Index     : in     Index_Type;
>>       Process   : not null access procedure (Element : in out Element_Type));
>> 
>> What is meant by this "not null"?  Is this available in ADA95, or new
>> to ADA05?
> 
> New to Ada 2005.  "Not null" means there's a run-time check that the
> pointer is not null.  It's pretty annoying that in order to pass a
> procedure as a parameter, you have to say the noise words "not null access",
> but that was considered necessary for compatibility.

Were subroutine types considered?

procedure Update_Element
     (Container : in out Vector;
       Index     : in Index_Type;
      Process   : in procedure (Element : in out Element_Type));

type Call_Back is procedure (...);

etc

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de