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!reader02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: why access parameter in stream attributes to begin with, instead of in or in/out ? Date: Tue, 12 Jun 2018 10:30:25 +0200 Organization: Aioe.org NNTP Server Message-ID: References: NNTP-Posting-Host: MyFhHs417jM9AgzRpXn7yg.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:52.0) Gecko/20100101 Thunderbird/52.8.0 X-Notice: Filtered by postfilter v. 0.8.3 Content-Language: en-US Xref: reader02.eternal-september.org comp.lang.ada:53061 Date: 2018-06-12T10:30:25+02:00 List-Id: On 2018-06-12 08:28, Mehdi Saada wrote: > Oh... Understood. In the first draft/drafts, functions were in/out, that was forsaken for the sake of purity from side-effects, then for the sake of the said side-effects access parameters are added (don't know if dispatching on access parameters/results were added at the same moment), yet they waited one more version to put back in-out function parameters... Surely there are many reasons (probably) but it still seems funny. There was no clear understanding of the contracts back then. Absence of side effects is a behavioral contract #1. It is different from absence of effects on the parameters #2. One can have any combination of these two. The choice was to have functions with any side effects allowed but no effects on the parameters except the dedicated one = the result. It was a pragmatic choice because that time it was impossible to have contracts on the side effects. Now we have SPARK and profiles, it should be possible. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de