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: stopping a loop iteration without exiting it Date: Fri, 12 Jan 2018 09:20:45 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <81971548-23c9-4927-a6a8-6f0f1dba896b@googlegroups.com> <5879f25e-c825-4c84-a219-293d1508b33d@googlegroups.com> 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/52.5.2 X-Notice: Filtered by postfilter v. 0.8.2 Content-Language: en-US Xref: reader02.eternal-september.org comp.lang.ada:49878 Date: 2018-01-12T09:20:45+01:00 List-Id: On 11/01/2018 21:54, G. B. wrote: > Dmitry A. Kazakov wrote: > >>>> I have no idea what this is supposed to mean. >>> >>> >>> L: >>> [for|while...] loop >>> ... >>> goto L; >>> ... >>> end loop L; >>> >>> Both outer Ls are part of what indicates the beginning >>> and end of the loop, resp. So, as others said in this thread, >>> there is syntactical ambiguity when using L with goto. >>> The meaning of the goto L is not clear or agreed upon >>> either, as readers here have said. >> >> Substitute "exit" for "goto" and reread your text. > > When writing, I also thought about “return” and about > exceptions, not just about “exit”. But none of them has > the potential of driving the iterative process, they just > leave it, the building block. It will be over. So what? In either case actions are non-trivial because they potentially involve finalization of objects and types. > loop is intended for the opposite, for when it’s not over yet. > For when it’s done again. “exit” cannot mean that, but the > hypothesized goto can. 1. "exit" can: exit when ; When condition evaluates false the loop continues. 2. "goto" cannot in any deeper sense than "exit" does because it is not "goto" which would drive the loop in this case. >>> A loop statement is a means of controlling flow. So is goto. >>> A loop controls iteration. Suppose that an additional >>> goto is needed to express that. Then this thread will >>> have discovered that Ada loops are deficient as building >>> blocks of iteration. >> >> Substitute "if" for "goto". > > Actually, “if” itself cannot directly make the program > iterate, unlike “goto”. Not in the case at hand. P.S. Take if + a subroutine call. That gives recursion. Then following your flawed logic either if or loop is bad. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de