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Re: should c be a subset of c++?

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James Kuyper <jameskuyper@verizon.net> writes:

> On 11/06/2015 08:15 PM, Ben Bacarisse wrote:
>> "J. Clarke" <j.clarke.873638@gmail.com> writes:
>> 
>>> In article <87egibhe03.fsf@bsb.me.uk>, ben.usenet@bsb.me.uk says...
>>>>
>>>> "Rick C. Hodgin" <rick.c.hodgin@gmail.com> writes:
>> <snip>
>>>>> They are not their conceptual
>>>>> representations of those real-world values, such as pi.  In order to
>>>>> use pi in the real world, as applied to something physical, it has to
>>>>> be translated from the concept of pi in a formula, which has an unending
>>>>> sequence of decimals, and approximated to a numerical value that is
>>>>> terminating at whatever resolution is required or possible.
>>>>
>>>> And yet there are calculations involving pi, ones that produce numerical
>>>> results that an engineer can use, that don't need pi to be approximated.
>>>
>>> Could you given an example of such a calculation that does not cancel pi 
>>> in some manner?
>> 
>> I'm not sure I know what you mean by cancel but I suspect the answer is
>> no, I can't.  All I can do (and I could swear I did in the original
>> thread) is support what I said.  I recall an example of an integral with
>> an exact answer.  That is an example of what I mean, even though it's
>> probably not an example of what you want.
>
> By "cancel", he means that the fact that the number can be calculated
> without relying upon the value of pi is because the calculation
> involves, for instance, multiplying by pi during one step, and then
> later dividing by it.

Yes, that must be one of the meanings.  I was not in doubt about that
simple example.  I'd prefer a definition because without one how can I
possibly answer?  I suspect the other ways that something can be said to
"cancel out" will simply cover (by definition) every case where the
result is an exact rational.

But I never made any claim about cancelling or not cancelling.  I said
that computations involving pi can be made that don't use an
approximation of pi.

> By rearranging the calculations, 'pi' drops out,
> rendering it's numerical value irrelevant. Such a calculation does not
> meaningfully involve pi, though it can be organized in a way that it
> appears to. I don't really see how a calculation that meaningfully
> involves pi can be reduced to an actual numerical value without using an
> approximation to pi.

I don't know what you mean by meaningful.  I suspect that any example I
give could be deemed not to use pi in a meaningful way.  It feels like a
"no true Scotsman trap".

> I want to be clear about the fact that I am not in any way endorsing
> Rick Hodgin's mathematical nonsense - I'm just curious about a claim
> made about the necessity (or lack thereof) of approximating pi.
>
>>>> pointing it out.  You can borrow Malcolm's phrase and say "ah, but only
>>>> when pi cancels out" if that makes you feel better about it.
>>>
>>> People would be more inclined to "agree with that simple fact" if you 
>>> supported it with evidence.
>> 
>> I did, didn't I?
>
> I used Google Groups to review previous messages in this thread. I
> didn't notice any specific examples of such a calculation. I might not
> have looked in the right place. Could you repeat the example, or at
> least provide a link to it?

I gave two in various places.  One was the integral of sin(x) from 0 to
pi.  Symbolic maths packages will give the answer 2 exactly without
using any approximation.  I also gave the example of computing e^(pi.i)
to get -1 but that was in a side subthread about what constitutes a
"computation".

-- 
Ben.

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Thread

Re: should c be a subset of c++? "J. Clarke" <j.clarke.873638@gmail.com> - 2015-11-06 19:02 -0500
  Re: should c be a subset of c++? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-07 01:15 +0000
    Re: should c be a subset of c++? James Kuyper <jameskuyper@verizon.net> - 2015-11-06 20:51 -0500
      Re: should c be a subset of c++? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-07 03:07 +0000
        Re: should c be a subset of c++? James Kuyper <jameskuyper@verizon.net> - 2015-11-06 23:45 -0500
          Re: should c be a subset of c++? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-07 06:39 +0000
            Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-07 00:45 -0800
              Re: should c be a subset of c++? supercat@casperkitty.com - 2015-11-07 16:37 -0800
                Re: should c be a subset of c++? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-07 16:45 -0800
                Re: should c be a subset of c++? supercat@casperkitty.com - 2015-11-08 08:14 -0800
                Re: should c be a subset of c++? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-08 09:42 -0800
                Re: should c be a subset of c++? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-08 21:43 +0000
                Re: should c be a subset of c++? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-08 13:53 -0800
                Re: should c be a subset of c++? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-08 13:56 -0800
                Re: should c be a subset of c++? supercat@casperkitty.com - 2015-11-08 14:27 -0800
                Re: should c be a subset of c++? Richard Heathfield <rjh@cpax.org.uk> - 2015-11-08 21:56 +0000
                Re: should c be a subset of c++? David Brown <david.brown@hesbynett.no> - 2015-11-08 23:05 +0100
                Re: should c be a subset of c++? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-08 14:20 -0800
                Re: should c be a subset of c++? David Brown <david.brown@hesbynett.no> - 2015-11-09 10:10 +0100
                Re: should c be a subset of c++? Geoff <geoff@invalid.invalid> - 2015-11-13 14:25 -0800
                Re: should c be a subset of c++? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-11-13 17:32 -0500
                Re: should c be a subset of c++? Geoff <geoff@invalid.invalid> - 2015-11-13 15:38 -0800
                Re: should c be a subset of c++? raltbos@xs4all.nl (Richard Bos) - 2015-11-10 17:01 +0000
                Re: should c be a subset of c++? Richard Heathfield <rjh@cpax.org.uk> - 2015-11-10 17:15 +0000
                Re: should c be a subset of c++? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-11-08 17:47 -0500
                Re: should c be a subset of c++? David Brown <david.brown@hesbynett.no> - 2015-11-08 23:04 +0100
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-08 14:22 -0800
                Re: should c be a subset of c++? supercat@casperkitty.com - 2015-11-08 14:31 -0800
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-08 14:38 -0800
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-08 19:50 -0500
                Re: should c be a subset of c++? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-09 01:36 +0000
                Re: should c be a subset of c++? David Brown <david.brown@hesbynett.no> - 2015-11-09 12:33 +0100
                Re: should c be a subset of c++? raltbos@xs4all.nl (Richard Bos) - 2015-11-10 17:03 +0000
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-08 19:24 -0500
                Re: should c be a subset of c++? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-09 01:16 +0000
                Re: should c be a subset of c++? raltbos@xs4all.nl (Richard Bos) - 2015-11-10 17:06 +0000
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-08 14:55 -0500
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-08 12:03 -0800
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-08 20:01 -0500
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-09 02:31 -0800
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-09 08:19 -0500
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-09 08:47 -0800
                Re: should c be a subset of c++? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-09 22:45 +0000
                Re: should c be a subset of c++? Keith Thompson <kst-u@mib.org> - 2015-11-09 14:56 -0800
                Re: should c be a subset of c++? supercat@casperkitty.com - 2015-11-09 15:24 -0800
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-09 15:56 -0800
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-09 21:54 -0500
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-09 19:07 -0800
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-10 08:37 -0500
                Re: should c be a subset of c++? raltbos@xs4all.nl (Richard Bos) - 2015-11-10 17:07 +0000
                Re: should c be a subset of c++? supercat@casperkitty.com - 2015-11-08 12:35 -0800
                Re: should c be a subset of c++? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-08 13:02 -0800
                Re: should c be a subset of c++? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-08 21:40 +0000
                Trig functions and radians supercat@casperkitty.com - 2015-11-08 13:54 -0800
                Re: should c be a subset of c++? Geoff <geoff@invalid.invalid> - 2015-11-13 14:18 -0800
                Re: should c be a subset of c++? supercat@casperkitty.com - 2015-11-13 14:55 -0800
                Re: should c be a subset of c++? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-08 01:02 +0000
                Re: should c be a subset of c++? Richard Damon <Richard@Damon-Family.org> - 2015-11-07 20:39 -0500

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