Re: A little puzzle.

From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.programming
Subject	Re: A little puzzle.
Date	2022-12-02 00:22 +0000
Organization	A noiseless patient Spider
Message-ID	<87pmd28xjj.fsf@bsb.me.uk> (permalink)
References	(5 earlier) <86k03k7yqe.fsf@linuxsc.com> <87o7stisxy.fsf@bsb.me.uk> <tltmbd$su3$1@gioia.aioe.org> <875yf1i26r.fsf@bsb.me.uk> <86wn7b5mru.fsf@linuxsc.com>

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Tim Rentsch <tr.17687@z991.linuxsc.com> writes:

> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>
>> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> 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).

For me, the negated recursive call was a sort of "ah ha!" moment.  I was
ploughing forwards trying to work out this and that case when a
light-bulb went off.

Above I say "it explained the non-trivial case more clearly" but that's
lazy wording and does not capture what I meant.  Rather than explaining
anything, I want code that is easy to verify.  I want, with just a
little thought, to know it's right.

> 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.

I've got rather fond of it as a question.  I don't conduct any
interviews anymore or I would be tempted to use it.

-- 
Ben.

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A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-21 20:45 +0000
  Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-21 22:06 +0100
    Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-21 21:21 +0000
      Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-22 09:17 +0100
        Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-11-22 11:07 +0000
          Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-22 15:17 +0100
        Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-22 11:40 +0000
          Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-22 15:26 +0100
            Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-22 15:28 +0000
              Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-22 16:30 +0100
      Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-22 09:23 +0100
        Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-11-22 11:08 +0000
        Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-22 12:54 +0000
  Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-21 17:39 -0800
    Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-22 13:00 +0000
      Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-22 05:31 -0800
  Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-11-22 11:04 +0000
    Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-22 12:53 +0000
      Re: A little puzzle. Paul N <gw7rib@aol.com> - 2022-11-22 05:01 -0800
        Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-22 05:48 -0800
          Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-22 15:31 +0100
      FFs [was Re: A little puzzle] Richard Harnden <richard.nospam@gmail.com> - 2022-11-22 16:29 +0000
    Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-12-14 13:57 +0000
      Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-12-14 13:58 +0000
      Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-12-14 16:22 +0000
  Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-22 05:24 -0800
    Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-22 15:23 +0000
      Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-23 08:04 -0800
        Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-24 00:06 +0000
          Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-11-24 04:06 +0000
            Re: A little puzzle. David Brown <david.brown@hesbynett.no> - 2022-11-24 09:29 +0100
              Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-24 13:23 +0000
            Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-24 13:14 +0000
              Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-11-24 14:00 +0000
                Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-24 14:59 +0000
                Re: A little puzzle. Richard Harnden <richard.nospam@gmail.com> - 2022-11-24 19:00 +0000
                Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-24 20:36 +0000
              Re: A little puzzle. Andreas <nobody@me.com> - 2022-11-27 00:38 +0100
                Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-27 00:11 +0000
          Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-24 14:51 -0800
            Re: A little puzzle. "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2022-11-25 09:30 +0100
              Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-25 01:16 -0800
                Re: A little puzzle. "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2022-11-25 11:11 +0100
                Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-25 06:26 -0800
                Re: A little puzzle. "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2022-11-25 15:59 +0100
            Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-26 16:25 +0000
              Re: A little puzzle. "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2022-11-26 19:36 +0100
                Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-27 02:03 +0000
                Re: A little puzzle. "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2022-11-27 11:02 +0100
                Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-01 04:30 -0800
                Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-02 00:22 +0000
                Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-02 22:30 -0800
                Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-12-03 02:43 -0800
              Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-27 18:38 -0800
  Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-27 02:27 -0800
    Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-27 19:23 -0800
      Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-27 22:59 -0800
        Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-27 23:03 -0800
        Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-28 07:22 -0800
          Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-28 10:20 -0800
            Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-29 04:29 -0800
              Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-29 04:50 -0800
                Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-11-29 14:47 +0000
                Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-29 17:23 +0000
                Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-29 09:50 -0800
                Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-30 01:39 -0800
                Re: A little puzzle. Richard Heathfield <rjh@cpax.org.uk> - 2022-11-30 11:10 +0000
                Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-30 02:24 -0800
                Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-30 06:28 -0800
                Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-01 06:55 -0800
                Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-12-02 01:54 -0800
  Re: A little puzzle. Richard Harnden <richard.nospam@gmail.com> - 2022-11-28 11:20 +0000
    Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-28 07:30 -0800
      Re: A little puzzle. Richard Harnden <richard.nospam@gmail.com> - 2022-11-28 17:15 +0000
        Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-29 04:03 -0800
          Re: A little puzzle. Richard Harnden <richard.nospam@gmail.com> - 2022-11-29 15:03 +0000
            Re: A little puzzle. "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2022-11-29 16:13 +0100
              Re: A little puzzle. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-29 17:37 +0000
                Re: A little puzzle. "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2022-11-29 19:02 +0100
                Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-29 10:10 -0800
            Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-30 03:32 -0800
              Re: A little puzzle. Julio Di Egidio <julio@diegidio.name> - 2022-11-30 06:36 -0800
              Re: A little puzzle. Richard Harnden <richard.nospam@gmail.com> - 2022-11-30 15:21 +0000
                Re: A little puzzle. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-01 06:51 -0800

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