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: "functional" programming in Ada Date: Thu, 8 Mar 2018 09:23:51 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <896b83c6-83d4-4ffc-8c56-1481802ea8fd@googlegroups.com> <961c82e0-7d7e-48af-8751-916a3332ccc5@googlegroups.com> <1520428274.2488.155.camel@obry.net> NNTP-Posting-Host: MyFhHs417jM9AgzRpXn7yg.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 X-Notice: Filtered by postfilter v. 0.8.3 Content-Language: en-US Xref: reader02.eternal-september.org comp.lang.ada:50894 Date: 2018-03-08T09:23:51+01:00 List-Id: On 08/03/2018 04:34, Randy Brukardt wrote: > "Pascal Obry" wrote in message > news:1520428274.2488.155.camel@obry.net... > Le mercredi 07 mars 2018 à 02:52 -0800, Mehdi Saada a écrit : >>> Why not writing everything in the specs then ? Maybe the original >>> separation of specs and bodies is a mistake, in the light of recent >>> tools requirements. >> >> The spec is what is exposed to other units. >> >> The body is implementation details. >> >> The separation is to me one of the most important point in Ada. I think >> that all languages should have done that. It is an welcomed separation >> for software engineer. > > Right. And note that the specification has always contained elements which > are determined at runtime (that is, executed). For instance, even in Ada 83 > you could have a subtype like: > > subtype Dyn is Natural range 1 .. Some_Function; > > and to properly export Dyn, one has to execute code. Determined at run-time /= determined in a specific way. Even if evaluation of an expression is static, when that expression is an implementation, that thing has *nothing* to seek in the specifications. Specifications must be only specifications regardless when and how evaluated. > The various contracts (preconditions, postconditions, predicates, etc.) all > contain some executable code, and it is necessary for callers to be able to > understand those contracts. Expression functions help in this, while the > bulk of the implementation should remain in the body. These are not contracts if have any executable code, and more importantly, understanding cannot be achieved by exposing implementation/code. P.S. Contracts exist prior the program (programs, actuall) and surely prior to any execution of (any implementation of any programs under the contract). -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de