From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED.fn3LatRFkm9/xzEj7F2/NQ.user.gioia.aioe.org!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Is this actually possible? Date: Thu, 12 Dec 2019 15:32:16 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <36d45c82-2a6b-4c60-baeb-1a4aef5189c7@googlegroups.com> <69c7677b-4aec-4db2-b240-de6b69f762b9@googlegroups.com> <23879d99-f1b0-4ade-8f2a-e45014fa04a7@googlegroups.com> NNTP-Posting-Host: fn3LatRFkm9/xzEj7F2/NQ.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 Content-Language: en-US X-Notice: Filtered by postfilter v. 0.9.2 Xref: reader01.eternal-september.org comp.lang.ada:57716 Date: 2019-12-12T15:32:16+01:00 List-Id: On 2019-12-12 11:17, Lucretia wrote: > On Wednesday, 11 December 2019 21:34:15 UTC, Dmitry A. Kazakov wrote: >> On 2019-12-11 22:12, Lucretia wrote: >>> On Wednesday, 11 December 2019 19:58:54 UTC, Dmitry A. Kazakov wrote: >> >>>> If you need objects that could be packed into C arrays use a variant >>>> record with the choice discriminant having a default. >>> >>> But in my cases, a variant cannot be used. >> >> Why? You must know all variants in order to compute the array element >> size. In Ada you cannot have it either: > > Because it's a binding to a C record: https://github.com/Lucretia/aplug/blob/master/ladspa/src/ladspa.ads#L113 I cannot recognize problem there. P.S. You can take a look at GtkAda design. It deploys a typical model. C API have a user data void * field allocated in all C objects. GtkAda creates an Ada object, creates a C object. Sets the user field in the C object to point to the Ada object and passes the C object to GTK. That way the hierarchy of C objects has a parallel hierarchy of tagged Ada objects. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de