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| Message-ID | <4DD06C8B.319E@mindspring.com> (permalink) |
|---|---|
| Date | 2011-05-15 20:15 -0400 |
| From | pete <pfiland@mindspring.com> |
| Organization | PF |
| Newsgroups | comp.lang.c |
| Subject | Re: I need help |
| References | <04ee4fd1-29ef-4640-a906-22055187c1e4@glegroupsg2000goo.googlegroups.com> <iqm0nq$7st$1@dont-email.me> <iqph2n$1vh$1@speranza.aioe.org> <iqpkhl$c51$1@dont-email.me> <4DD065AF.184F@mindspring.com> |
pete wrote:
>
> Eric Sosman wrote:
> >
> > On 5/15/2011 5:37 PM, sandeep wrote:
> > > Eric Sosman writes:
> > >> char *space = strchr(karmarkar, ' '); if (space == NULL)
> > >> printf ("No spaces\n");
> > >> else
> > >> printf ("First space is at position %u\n",
> > >> (unsigned)(space - karmarkar));
> > >
> > > This could give the wrong answer on implementations
> > > where PTRDIFF_MAX > UINT_MAX.
> >
> > Thank you so very, very much for this helpful observation,
> > guaranteed to clarify matters for the O.P.
>
> sandeep is wrong.
> The context (snipped by sandeep)
> for which your code was written, is this:
> char* karmarkar = "Karmarkar 958572";
>
> And in that context, there is no way that the difference
> between (space) and (karmarkar) can excede either UINT_MAX
> or PTRDIFF_MAX (which would be a different C trivia point).
I should have been more clear.
Whether or not (PTRDIFF_MAX > UINT_MAX) is true, is irrelevant.
This code cannot give the wrong answer.
What matters,
in terms of whether or not the code is undefined,
is whether or not (space - karmarkar)
is representable as a ptrdiff_t value.
Since (space - karmarkar)
is representable as a ptrdiff_t value,
then what matters,
in terms of whether or not the code outputs the correct answer,
is whether or not (space - karmarkar)
is less than or equal to UINT_MAX.
--
pete
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I need help janus <emekamicro@gmail.com> - 2011-05-14 04:05 -0700
Re: I need help "Heinrich Wolf" <invalid@invalid.invalid> - 2011-05-14 13:30 +0200
Re: I need help "Joachim Schmitz" <jojo.nospam@schmitz-digital.de> - 2011-05-14 13:46 +0200
Re: I need help "Heinrich Wolf" <invalid@invalid.invalid> - 2011-05-14 14:20 +0200
Re: I need help Columbus sailed the ocean China Blue <chine.bleu@yahoo.com> - 2011-05-14 04:48 -0700
Re: I need help "Joachim Schmitz" <jojo.nospam@schmitz-digital.de> - 2011-05-14 13:39 +0200
Re: I need help "Joachim Schmitz" <jojo.nospam@schmitz-digital.de> - 2011-05-14 13:44 +0200
Re: I need help "Heinrich Wolf" <invalid@invalid.invalid> - 2011-05-14 14:23 +0200
Re: I need help "Joachim Schmitz" <jojo.nospam@schmitz-digital.de> - 2011-05-16 16:47 +0200
Re: I need help James Kuyper <jameskuyper@verizon.net> - 2011-05-14 09:14 -0400
Re: I need help "Joachim Schmitz" <jojo.nospam@schmitz-digital.de> - 2011-05-16 16:43 +0200
Re: I need help Keith Thompson <kst-u@mib.org> - 2011-05-16 08:23 -0700
Re: I need help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-05-16 23:00 +0100
Rationale for Shao Miller <sha0.miller@gmail.com> - 2011-05-16 23:40 -0500
Re: Rationale for Some of 6.7.3p9? Shao Miller <sha0.miller@gmail.com> - 2011-05-16 23:43 -0500
Re: Rationale for Some of 6.7.3p9? Heikki Kallasjoki <see@end.of.message.invalid> - 2011-05-17 06:06 +0000
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Re: Rationale for Some of 6.7.3p9? Angel <angel+news@spamcop.net> - 2011-05-17 14:03 +0000
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Re: Rationale for Ike Naar <ike@iceland.freeshell.org> - 2011-05-17 06:09 +0000
Re: Rationale for Shao Miller <sha0.miller@gmail.com> - 2011-05-17 10:20 -0400
Re: I need help Columbus sailed the ocean China Blue <chine.bleu@yahoo.com> - 2011-05-14 04:45 -0700
Re: I need help Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-05-14 09:39 -0400
Re: I need help sandeep <nospam@nospam.com> - 2011-05-15 21:37 +0000
Re: I need help Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-05-15 18:35 -0400
Re: I need help pete <pfiland@mindspring.com> - 2011-05-15 19:45 -0400
Re: I need help pete <pfiland@mindspring.com> - 2011-05-15 20:15 -0400
Re: I need help sandeep <nospam@nospam.com> - 2011-05-16 18:27 +0000
Re: I need help Shao Miller <sha0.miller@gmail.com> - 2011-05-16 14:45 -0400
Re: I need help Keith Thompson <kst-u@mib.org> - 2011-05-16 11:41 -0700
Re: I need help Seebs <usenet-nospam@seebs.net> - 2011-05-16 19:12 +0000
Re: I need help Keith Thompson <kst-u@mib.org> - 2011-05-16 12:30 -0700
Re: I need help Seebs <usenet-nospam@seebs.net> - 2011-05-16 20:09 +0000
Re: I need help sandeep <nospam@nospam.com> - 2011-05-16 20:35 +0000
Re: I need help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-05-16 23:22 +0100
Re: I need help David Thompson <dave.thompson2@verizon.net> - 2011-05-24 01:19 -0400
Re: I need help Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 00:19 -0700
Re: I need help Seebs <usenet-nospam@seebs.net> - 2011-05-19 14:37 +0000
Re: I need help Keith Thompson <kst-u@mib.org> - 2011-05-19 08:17 -0700
Re: I need help Seebs <usenet-nospam@seebs.net> - 2011-05-19 16:08 +0000
Re: I need help Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 11:13 -0700
Re: I need help Keith Thompson <kst-u@mib.org> - 2011-05-16 08:12 -0700
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