Groups > comp.lang.c > #71964

Re: Learning functions; roots of the quadratic; two return values

From	Bartc <bc@freeuk.com>
Newsgroups	comp.lang.c
Subject	Re: Learning functions; roots of the quadratic; two return values
Date	2015-10-05 12:20 +0100
Organization	A noiseless patient Spider
Message-ID	<mutmap$37d$1@dont-email.me> (permalink)
References	(1 earlier) <623fef72-989a-4973-9d04-b1a867a00703@googlegroups.com> <pnr21b1287fff5arfericujjih1vk7to5b@4ax.com> <5611ccfd$0$3060$426a34cc@news.free.fr> <jhr31b58dqnsrblak6mmiqjcbs98hvevop@4ax.com> <5612537a$0$3299$426a74cc@news.free.fr>

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On 05/10/2015 11:39, regis wrote:
> On 10/05/15 05:31, Rosario19 wrote:
>
>> do you want the correct name for variables?
>
> If you write: int myWeightInKg= 65; ...; myWeightInKg += 5;
>
> the value of myWeightInKg changes, but not its meaning:
> I'm heavier by 5 kilograms, but it's still my weight in kilograms.

OK, here myWeightInKg clearly refers to a physical quantity with a 
certain 'dimension'. So you couldn't do myWeightInKg *= myWeightInKg as 
the dimension then becomes kg-squared (with no meaning afaik).

> But when you write: double delta= b*b-4*a*c; ...; delta= sqrt(delta);
> Things are different: You don't just change the value here,
> you also change the meaning of delta.

But what's delta? Isn't it just a number? (Until now I'd never even 
heard of delta in connection with solving quadratic equations).

> It once meant the discriminant as it should
> (as delta is universally used to denote the discriminant),
> and then you make its name a liar by changing its meaning.
>
> So you should use 2 variables here: sqrtDelta= sqrt (delta);

> Never use meaningless names for identifiers.

So you'd never use x, y, z? My math(s) textbooks used to be full of 
them! What about the a, b, c used for the coefficients of the equation?

> Never use a meaning for another in identifier names.
> Never change the meaning of a variable during its lifetime.

Sometimes that makes sense; if DataArray points to an int array for 
example, you don't to step DataArray along itself, because at the end if 
won't refer to the original array at all.

But otherwise I think you're worrying too much!

-- 
Bartc

Thread

Learning functions; roots of the quadratic; two return values Alla _ <modelling.data@gmail.com> - 2015-10-03 10:43 -0700
  Re: Learning functions; roots of the quadratic; two return values Andrew Cooper <amc96@cam.ac.uk> - 2015-10-03 19:00 +0100
    Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-03 19:34 +0100
      Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-03 21:29 +0200
        Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-03 21:36 +0200
        Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-03 21:43 +0200
        Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-03 20:46 +0100
          Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-03 22:46 +0200
            Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-03 23:18 +0100
              Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-04 01:08 +0200
              Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-04 01:36 +0200
                Re: Learning functions; roots of the quadratic; two return values Ian Collins <ian-news@hotmail.com> - 2015-10-04 12:52 +1300
                Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-04 15:42 +0100
          Re: Learning functions; roots of the quadratic; two return values jacobnavia <jacob@jacob.remcomp.fr> - 2015-10-03 23:05 +0200
            Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-03 23:41 +0200
              Re: Learning functions; roots of the quadratic; two return values jacobnavia <jacob@jacob.remcomp.fr> - 2015-10-04 00:14 +0200
            Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-03 23:07 +0100
              Re: Learning functions; roots of the quadratic; two return values jacobnavia <jacob@jacob.remcomp.fr> - 2015-10-04 00:32 +0200
              Re: Learning functions; roots of the quadratic; two return values Keith Thompson <kst-u@mib.org> - 2015-10-04 12:56 -0700
                Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-04 23:41 +0100
                Re: Learning functions; roots of the quadratic; two return values Keith Thompson <kst-u@mib.org> - 2015-10-04 18:24 -0700
              Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-04 16:36 -0400
                Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-05 00:01 +0100
                Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-04 19:24 -0400
          Re: Learning functions; roots of the quadratic; two return values Ian Collins <ian-news@hotmail.com> - 2015-10-04 10:18 +1300
            Re: Learning functions; roots of the quadratic; two return values jacobnavia <jacob@jacob.remcomp.fr> - 2015-10-03 23:27 +0200
              Re: Learning functions; roots of the quadratic; two return values Ian Collins <ian-news@hotmail.com> - 2015-10-04 11:08 +1300
                Re: Learning functions; roots of the quadratic; two return values Richard Damon <Richard@Damon-Family.org> - 2015-10-03 18:38 -0400
                Re: Learning functions; roots of the quadratic; two return values Ian Collins <ian-news@hotmail.com> - 2015-10-04 11:47 +1300
          Re: Learning functions; roots of the quadratic; two return values raltbos@xs4all.nl (Richard Bos) - 2015-10-04 14:07 +0000
            Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-04 15:48 +0100
              Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-04 18:59 +0200
                Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-04 20:06 +0200
              Re: Learning functions; roots of the quadratic; two return values Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 15:21 -0700
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 05:25 +0000
        Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-03 21:48 +0200
          Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-04 00:31 +0200
    Re: Learning functions; roots of the quadratic; two return values alla.rashitova@gmail.com - 2015-10-05 08:40 -0700
      Re: Learning functions; roots of the quadratic; two return values Richard Heathfield <rjh@cpax.org.uk> - 2015-10-05 17:10 +0100
      Re: Learning functions; roots of the quadratic; two return values Barry Schwarz <schwarzb@dqel.com> - 2015-10-05 10:41 -0700
  Re: Learning functions; roots of the quadratic; two return values "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-03 12:04 -0700
    Re: Learning functions; roots of the quadratic; two return values Philip Lantz <prl@canterey.us> - 2015-10-03 12:48 -0700
    Re: Learning functions; roots of the quadratic; two return values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-03 20:55 +0100
      Re: Learning functions; roots of the quadratic; two return values "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-03 13:27 -0700
      Re: Learning functions; roots of the quadratic; two return values jacobnavia <jacob@jacob.remcomp.fr> - 2015-10-03 23:08 +0200
        Re: Learning functions; roots of the quadratic; two return values Richard Heathfield <rjh@cpax.org.uk> - 2015-10-03 22:52 +0100
    Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-04 20:46 +0200
      Re: Learning functions; roots of the quadratic; two return values Keith Thompson <kst-u@mib.org> - 2015-10-04 15:47 -0700
      Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-05 03:06 +0200
        Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-05 05:31 +0200
          Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-05 11:58 +0200
            Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-05 12:00 +0200
              Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-05 12:06 +0200
          Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-05 12:39 +0200
            Re: Learning functions; roots of the quadratic; two return values Bartc <bc@freeuk.com> - 2015-10-05 12:20 +0100
              Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-05 13:50 +0200
              Re: Learning functions; roots of the quadratic; two return values Richard Heathfield <rjh@cpax.org.uk> - 2015-10-05 12:57 +0100
        Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 05:40 +0000
          Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-05 08:30 +0200
          Re: Learning functions; roots of the quadratic; two return values Philip Lantz <prl@canterey.us> - 2015-10-05 10:03 -0700
            Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 22:25 +0000
              Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-05 19:26 -0400
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 03:44 +0000
                Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-06 10:55 -0400
                Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-06 23:07 +0200
                Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-06 18:35 -0400
                Re: Learning functions; roots of the quadratic; two return values raltbos@xs4all.nl (Richard Bos) - 2015-10-14 11:08 +0000
                Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-14 11:11 -0400
                Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-14 22:22 +0200
                Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-14 17:17 -0400
                Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-14 23:45 +0200
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-15 00:11 +0000
                Re: Learning functions; roots of the quadratic; two return values Bartc <bc@freeuk.com> - 2015-10-15 01:37 +0100
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-15 05:52 +0000
                Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-14 21:54 -0400
                Re: Learning functions; roots of the quadratic; two return values asetofsymbols@gmail.com - 2015-10-14 22:40 -0700
                Re: Learning functions; roots of the quadratic; two return values asetofsymbols@gmail.com - 2015-10-15 05:00 -0700
                Re: Learning functions; roots of the quadratic; two return values supercat@casperkitty.com - 2015-10-15 11:58 -0700
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-15 06:04 +0000
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 23:18 +0000
                Re: Learning functions; roots of the quadratic; two return values supercat@casperkitty.com - 2015-10-06 16:31 -0700
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-07 00:38 +0000
                Re: Learning functions; roots of the quadratic; two return values supercat@casperkitty.com - 2015-10-06 21:19 -0700
                Re: Learning functions; roots of the quadratic; two return values James Kuyper <jameskuyper@verizon.net> - 2015-10-06 22:15 -0400
                Re: Learning functions; roots of the quadratic; two return values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-07 08:45 +0000
                Re: Learning functions; roots of the quadratic; two return values Melzzzzz <mel@zzzzz.com> - 2015-10-07 05:19 +0200
                Re: Learning functions; roots of the quadratic; two return values Keith Thompson <kst-u@mib.org> - 2015-10-07 09:12 -0700
                Re: Learning functions; roots of the quadratic; two return values Melzzzzz <mel@zzzzz.com> - 2015-10-08 00:53 +0200
                Re: Learning functions; roots of the quadratic; two return values Keith Thompson <kst-u@mib.org> - 2015-10-07 16:23 -0700
              Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-06 02:16 +0200
                Re: Learning functions; roots of the quadratic; two return values supercat@casperkitty.com - 2015-10-06 15:43 -0700
                Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-07 02:48 +0200
                Re: Learning functions; roots of the quadratic; two return values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-14 14:00 -0700
                Re: Learning functions; roots of the quadratic; two return values regis <regis.barbanchon@free.fr> - 2015-10-14 23:23 +0200
  Re: Learning functions; roots of the quadratic; two return values Geoff <geoff@invalid.invalid> - 2015-10-03 12:50 -0700
  Re: Learning functions; roots of the quadratic; two return values Bartc <bc@freeuk.com> - 2015-10-03 21:16 +0100
    Re: Learning functions; roots of the quadratic; two return values alla.rashitova@gmail.com - 2015-10-05 09:02 -0700
      Re: Learning functions; roots of the quadratic; two return values Richard Heathfield <rjh@cpax.org.uk> - 2015-10-05 17:13 +0100
  Re: Learning functions; roots of the quadratic; two return values Barry Schwarz <schwarzb@dqel.com> - 2015-10-03 15:37 -0700
  Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-05 23:44 +0200
    Re: Learning functions; roots of the quadratic; two return values Geoff <geoff@invalid.invalid> - 2015-10-05 18:37 -0700
    Re: Learning functions; roots of the quadratic; two return values Barry Schwarz <schwarzb@dqel.com> - 2015-10-05 19:24 -0700
      Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-06 07:36 +0200
    Re: Learning functions; roots of the quadratic; two return values Rosario19 <Ros@invalid.invalid> - 2015-10-06 07:34 +0200

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