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 X-Received: by 2002:a24:dc05:: with SMTP id q5mr12421177itg.123.1560112504094; Sun, 09 Jun 2019 13:35:04 -0700 (PDT) X-Received: by 2002:a9d:6b83:: with SMTP id b3mr27471446otq.82.1560112503882; Sun, 09 Jun 2019 13:35:03 -0700 (PDT) Path: eternal-september.org!reader01.eternal-september.org!feeder.eternal-september.org!news.gegeweb.eu!gegeweb.org!usenet-fr.net!proxad.net!feeder1-2.proxad.net!209.85.166.216.MISMATCH!g15no615443itd.0!news-out.google.com!l135ni697itc.0!nntp.google.com!g15no615439itd.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Sun, 9 Jun 2019 13:35:03 -0700 (PDT) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=2601:3c3:401:f550:cd4d:1fbd:b00b:70c3; posting-account=JSxOkAoAAADa00TJoz2WZ_46XrZCdXeS NNTP-Posting-Host: 2601:3c3:401:f550:cd4d:1fbd:b00b:70c3 References: <28facad3-c55f-4ef2-8ef8-004925b7d1f1@googlegroups.com> <87woi0xtwm.fsf@nightsong.com> <4a0438de-1f1d-4469-aae4-908854d378ea@googlegroups.com> <47d02bdc-6b50-43aa-bc5d-bb5b6225f5bd@googlegroups.com> <455333f0-ede4-4833-900a-240a499395ac@googlegroups.com> <875zphvufc.fsf@nightsong.com> <87y32bvbeo.fsf@nightsong.com> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <561c766c-4f9c-432c-be9b-822dd9c3c8ba@googlegroups.com> Subject: Re: Why .ads as well as .adb? From: John Perry Injection-Date: Sun, 09 Jun 2019 20:35:04 +0000 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Xref: reader01.eternal-september.org comp.lang.ada:56587 Date: 2019-06-09T13:35:03-07:00 List-Id: (1) Ada's approach has one advantage that I don't remember anyone mentionin= g (apologies if you did and I missed it or forgot): I can't remember the number of times I modified a C++ / Eiffel / Java / Obe= ron / whatever file, and forgot to update the documentation. So now the spe= cification / documentation and the implementation are out of sync, and in m= y experience nothing is harder to debug than a wrongly documented specifica= tion. In Ada, if you forget to update the specification file, your system probabl= y won't compile. The language thus forces you to update that. That said... (2) I've read some very good arguments made in favor of separate specificat= ion files, but I don't understand why the conversation keeps coming around = to "the specification file provides convenient documentation," or even, "if= I want to see the specification from the implementation, I have to run a t= ool every time I want to see it, and that can be inconvenient." Those aren'= t just weak arguments; they're plainly false. When I want to know how Ada.Text_IO works, I don't look up the specificatio= n file. I don't even know where to find Ada.Text_IO on my system. I just we= nt to look for it, and gave up pretty quickly. I could probably find it if = I tried hard enough, but it's far more convenient to visit [1], which has a= hyperlink to Ada.Text_IO, as well as lots of other things. I imagine that [1] was generated by some software tool. Similar tools exist= for other languages. Take a look at [2] to see what a nice job they can do= -- a LOT nicer than [1]. If I click on BINARY_SEARCH_TREE, not only do I g= et the specification for BINARY_SEARCH_TREE a la [1], but I also get links = to related specifications, such as COMPARABLE, TREE_ITERATION_CURSOR, and s= o forth. This is much, _much_ more helpful than the specification file by i= tself. Some have suggested that the markup required to do this can make the source= file unreadable. Eiffel's source files are some of the most readable I've = ever encountered, certainly no less readable than Ada (IMHO). Doxygen and j= avadoc markup aren't especially painful to read, either, and they do much t= he same thing. Moreover, there's no need to invoke such a tool every time you want to see = the specification, and thus no inconvenience at all. You generate the speci= fication / documentation once and it ends up in a file that you can distrib= ute just as easily as an .ads. The only time one has to invoke Doxygen, jav= adoc, etc. is if the exported objects change. The downside is that you *have* to remember to update the documentation -- = something I usually do remember, but not always. That's what made me think = that Ada's approach does offer an advantage here (see above). [1] http://www.ada-auth.org/standards/12rm/html/RM-TOC.html [2] https://www.eiffel.org/files/doc/static/19.05/libraries/base/index.html