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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Interresting,
 possibly buggy behavior in GNAT generics w/ expression function.
Date: Tue, 2 Apr 2013 10:51:31 +0200
Organization: cbb software GmbH
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Date: 2013-04-02T10:51:31+02:00
List-Id: <comp.lang.ada>

On Mon, 1 Apr 2013 19:52:10 -0500, Randy Brukardt wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
> news:1ilubaaaex6jp$.zd9lslst85nn.dlg@40tude.net...

>> You lumped together two different contracts. There is a contract on the
>> actual parameters which is defined by be the formal parameters
>> specification. Another contract is the generic package specification
>> (public part), which is a contract for the clients using an instance of 
>> the package.
> 
> No I didn't - I'm only talking about the contract of a generic unit.

It is more than one contract because a generic unit is used in two
completely different contexts:

1. Instantiation

2. Use of the instance

> The 
> case in question is the meaning of "not overriding" in a generic 
> speecification. Uses of overriding indicators in a generic specification is 
> part of the contract of the generic, as are various other things (like 
> accessibility checks - it's easy to write a generic that can only be 
> instantiated at library level).

Considering the contract #1 it is a language design error. This contract
should be limited strictly to the formal part, IMO. Impossibility to
achieve that is one of multiple problems all macro expansions have (Ada
generics included).

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