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!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Generators/coroutines in future Ada? Date: Wed, 12 Jul 2017 09:19:56 +0200 Organization: Aioe.org NNTP Server Message-ID: References: NNTP-Posting-Host: vZYCW951TbFitc4GdEwQJg.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/52.2.1 Content-Language: en-US X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:47373 Date: 2017-07-12T09:19:56+02:00 List-Id: On 12/07/2017 01:19, Victor Porton wrote: > Dmitry A. Kazakov wrote: > >> On 2017-07-11 21:22, J-P. Rosen wrote: >>> Le 11/07/2017 à 20:36, Victor Porton a écrit : >>>> This state also includes the point of execution (like "We are in the >>>> second loop in its second operator.") >>>> >>>>> This can easily be achieved with a function within a package, where the >>>>> package serves to protect and hide the function's state. >>>> Ada currently has no support to save such (point of execution) states. >>> It has. Make your generator a task, and have an accept when the data is >>> ready, which can be nested as deep as you want in any construct. >>> >>> A task is a perfect abstraction for a thread of control that maintains >>> its own execution state! >> >> Except that no control is required. >> >> I don't understand what is wrong with: >> >> type Stateful is limited private; >> function Generate (X : not null access Stateful) return Things; > > The thing "wrong" with this, is that it is sometimes hard to implement > Generate(). In Python this can be done in an easier way by using generators > (Python's "yield" keywords). That would be a co-routine rather than merely a stateful execution. These are not same. Regarding co-routines J-P already answered it, a task is exactly what a co-routine is, except for external scheduling. To have co-routines in Ada everything one needs is user-defined explicit scheduling. 'Yield' belongs there. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de