Path: csiph.com!1.us.feeder.erje.net!3.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!reader01.eternal-september.org!.POSTED!not-for-mail From: Tim Rentsch Newsgroups: comp.programming Subject: Re: A little puzzle. Date: Thu, 01 Dec 2022 04:30:45 -0800 Organization: A noiseless patient Spider Lines: 40 Message-ID: <86wn7b5mru.fsf@linuxsc.com> References: <875yf8nijb.fsf@bsb.me.uk> <865yf79l66.fsf@linuxsc.com> <87wn7nj9mb.fsf@bsb.me.uk> <86sfi98xnx.fsf@linuxsc.com> <87leo1i5bo.fsf@bsb.me.uk> <86k03k7yqe.fsf@linuxsc.com> <87o7stisxy.fsf@bsb.me.uk> <875yf1i26r.fsf@bsb.me.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: reader01.eternal-september.org; posting-host="67b01cddb462709762c0c460072e4ec7"; logging-data="2949833"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18zeD+5osdt+b+W8vagTQJXCAtgKDR4j2Q=" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:qSKyu0cPu9kwR5Eh5L7OW3f41R8= sha1:mum6I080ghEBvsMSG0BHNBdznlk= Xref: csiph.com comp.programming:16018 Ben Bacarisse writes: > "Dmitry A. Kazakov" writes: [...] >> function Flight_East_Crosses_Longitude >> ( Start, Stop, X : Longtitude >> ) return Boolean is >> begin >> if Start <= Stop then >> return X in Start..Stop; >> else >> return X <= Stop or else X >= Start; >> end if; >> end Flight_East_Crosses_Longitude; > > Except for some boundary cases [ie, the region being half open] that > have got lost in the telling, this is similar to Tim's solution. I > chose to use a recursive call, because I though it explained the > non-trivial case more clearly (but I bet I am pretty much the only > one who thinks that). I want to add something here to my earlier comment. The idea of using a recursive call reflects a deeper understanding of what "circular regions" are. If one has already assimilated that understanding then I think the recursive call is "more obvious", in the sense that it takes less thought, or I might say less additional thought. I didn't have that background (and didn't develop it while solving the problem) so for me the cruder but more direct approach was easier to see. Bottom line, I don't think either formulation is uniformly "easier to understand" than the other; it depends on one's background (or ability to develop a suitable understanding on the fly, which in this case I did not possess). This problem provides an example where it helps to see both approaches to solving the problem, to see how they relate to each other, but also to give an appreciation for the power of having more advanced tools available in the mental toolbox.