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| From | Richard Heathfield <rjh@cpax.org.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Portable 16 bit binary integer write |
| Date | 2016-09-26 10:25 +0100 |
| Organization | Fix this later |
| Message-ID | <nsaphq$4c4$1@dont-email.me> (permalink) |
| References | (17 earlier) <26b1209d-868e-49f4-a211-3d0f1019759d@googlegroups.com> <ln7fa1uh4z.fsf@kst-u.example.com> <177ae31d-6836-4448-9edd-339cf95aa974@googlegroups.com> <lnr387tyge.fsf@kst-u.example.com> <d03226bb-e691-4ad7-814c-ce2b89bea46c@googlegroups.com> |
On 26/09/16 10:08, Malcolm McLean wrote:
> On Sunday, September 25, 2016 at 11:18:05 PM UTC+1, Keith Thompson wrote:
>> supercat@casperkitty.com writes:
>> [...]
>>> Given that compiler writers in the 1980s were able to accommodate code
>>> that was designed for 16-bit "int" even on 32-bit platforms, should it
>>> not have been reasonable to expect that by the time 64-bit platforms
>>> became common, compiler writers would have figured out how to sensibly
>>> handle code written for 32-bit "int"?
>>
>> Huh? In what sense do compilers for 64-bit platforms *not* sensibly
>> handle code written for 32-bit int?
>>
> The function
> double(mean(double *x, int N)
> {
> double total = 0;
> int i;
>
> for(i=0;i<N;i++)
> total += x[i];
>
> return total/N;
> }
>
> now breaks. We can create an array more than INT_max elements long,
> and so we will get the wrong answer if we try to take the mean
> using this perfectly unexceptional function.
Assuming you mean INT_MAX rather than INT_max. If the above code worked
on 32-bit int platforms, it'll work under the same conditions on 64-bit
int platforms. If the array was greater than INT_MAX elements long
before, it won't be now (assuming the absolute size of the array is the
same), so the code got less dodgy in the move to 64 bit, rather than the
reverse.
If you /still/ have an array greater than INT_MAX elements long because
you've defined it to be, say, INT_MAX + 6, then it's (a) a stupid design
and (b) easy to fix at least one of the stupidities of that decision.
Just use size_t instead:
#include <math.h>
#include <stddef.h>
double calc_arithmetic_mean(const double *x, size_t N)
{
double total = 0.0;
size_t i = 0;
while(i < N)
{
total += x[i];
}
return (N == 0) ? HUGE_VAL : (total / N);
}
All fixed. Use size_t, Malcolm. Now you can't create an array bigger
than the capacity of the loop counter, because the loop counter has all
the necessary range for dealing with any array.
The size_t type: you know it makes sense.
--
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within
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Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-10 14:23 -0700
Re: Portable 16 bit binary integer write Barry Schwarz <schwarzb@dqel.com> - 2016-09-10 17:11 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-11 07:00 -0700
Re: Portable 16 bit binary integer write Richard Damon <Richard@Damon-Family.org> - 2016-09-13 08:41 -0400
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-13 06:24 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-13 16:19 +0200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-13 10:20 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-13 11:07 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-13 20:47 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-14 08:24 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-15 12:17 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-15 11:27 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-15 09:03 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-15 11:21 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-15 18:39 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-15 12:26 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-15 23:12 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-15 16:17 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-15 18:35 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-16 11:10 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-16 08:43 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-16 19:59 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-16 13:34 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-16 16:23 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-16 15:31 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-16 19:06 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-16 23:27 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-17 15:04 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-17 20:35 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-18 00:09 -0700
Re: Portable 16 bit binary integer write Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-18 19:36 +0100
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-18 15:29 -0700
Re: Portable 16 bit binary integer write Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-19 01:20 +0100
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-18 09:48 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-18 19:38 +0200
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-18 15:33 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-18 13:58 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-18 14:15 -0700
Re: Portable 16 bit binary integer write BartC <bc@freeuk.com> - 2016-09-18 23:15 +0100
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-18 15:46 -0700
Re: Portable 16 bit binary integer write Ian Collins <ian-news@hotmail.com> - 2016-09-19 17:03 +1200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-19 07:40 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-19 10:54 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-19 10:51 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-19 22:03 +0200
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-19 15:44 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-20 09:02 +0200
Re: Portable 16 bit binary integer write BartC <bc@freeuk.com> - 2016-09-19 21:12 +0100
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-19 15:58 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-19 09:49 +0200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-19 02:37 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-19 13:20 +0200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-19 06:22 -0700
Re: Portable 16 bit binary integer write BartC <bc@freeuk.com> - 2016-09-19 12:46 +0100
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-19 16:20 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-19 07:32 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-19 11:26 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-19 09:10 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-19 09:33 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-19 11:54 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-19 22:14 +0200
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-19 22:12 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-19 14:32 -0700
Re: Portable 16 bit binary integer write Robert Wessel <robertwessel2@yahoo.com> - 2016-09-19 22:58 -0500
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-20 09:45 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-20 07:49 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-20 19:43 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-20 11:15 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-19 22:36 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-22 21:30 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-22 23:58 -0700
Re: Portable 16 bit binary integer write Ian Collins <ian-news@hotmail.com> - 2016-09-23 19:45 +1200
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-28 08:17 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-28 09:59 -0700
Re: Portable 16 bit binary integer write Ian Collins <ian-news@hotmail.com> - 2016-09-29 07:59 +1300
Re: Portable 16 bit binary integer write Ike Naar <ike@iceland.freeshell.org> - 2016-09-28 19:26 +0000
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-28 12:37 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-10-09 03:46 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-18 13:53 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-21 21:03 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-21 22:23 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-22 08:09 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-23 10:31 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-23 10:56 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-29 08:03 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-30 07:39 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-22 09:49 +0200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-22 08:34 -0700
Re: Portable 16 bit binary integer write BartC <bc@freeuk.com> - 2016-09-22 17:44 +0100
Re: Portable 16 bit binary integer write Melzzzzz <Melzzzzz@zzzzz.com> - 2016-09-22 17:16 +0000
Re: Portable 16 bit binary integer write BartC <bc@freeuk.com> - 2016-09-22 18:26 +0100
Re: Portable 16 bit binary integer write Melzzzzz <Melzzzzz@zzzzz.com> - 2016-09-22 17:33 +0000
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-23 10:23 +0200
Re: Portable 16 bit binary integer write Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-23 13:43 +0100
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-23 14:58 +0200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-22 18:14 -0700
Re: Portable 16 bit binary integer write luser droog <luser.droog@gmail.com> - 2016-09-22 20:28 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-23 00:12 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-22 10:57 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-23 10:18 +0200
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-23 11:48 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-23 15:58 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-29 08:21 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-30 07:42 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-23 23:38 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-24 11:42 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-24 14:13 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-24 23:03 -0700
Re: Portable 16 bit binary integer write Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-25 11:29 +0100
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-25 14:02 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-25 15:17 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-25 16:52 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-25 13:59 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-25 15:13 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-25 15:50 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-28 08:13 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-24 16:06 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-24 11:53 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-24 14:23 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-25 14:16 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-25 15:18 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-25 16:39 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-25 23:33 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-26 02:08 -0700
Re: Portable 16 bit binary integer write Richard Heathfield <rjh@cpax.org.uk> - 2016-09-26 10:25 +0100
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-26 03:05 -0700
Re: Portable 16 bit binary integer write Richard Heathfield <rjh@cpax.org.uk> - 2016-09-26 11:09 +0100
Re: Portable 16 bit binary integer write "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-09-26 09:29 -0700
Re: Portable 16 bit binary integer write Richard Heathfield <rjh@cpax.org.uk> - 2016-09-26 17:37 +0100
Re: Portable 16 bit binary integer write "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-09-26 12:29 -0700
Re: Portable 16 bit binary integer write BartC <bc@freeuk.com> - 2016-09-26 11:12 +0100
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-26 13:19 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-26 18:34 -0700
Re: Portable 16 bit binary integer write Ike Naar <ike@iceland.freeshell.org> - 2016-09-27 06:43 +0000
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-27 00:51 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-27 08:42 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-22 11:40 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-23 10:00 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-23 10:34 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-29 08:13 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-18 00:06 +0200
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-17 17:32 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-18 15:57 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-17 20:46 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-18 16:08 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-18 10:03 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-17 23:59 +0200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-17 16:49 -0700
Re: Portable 16 bit binary integer write Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-18 01:19 +0100
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-18 07:16 -0700
Re: Portable 16 bit binary integer write "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-18 10:19 -0400
Re: Portable 16 bit binary integer write luser droog <luser.droog@gmail.com> - 2016-09-18 13:26 -0700
Re: Portable 16 bit binary integer write "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-18 17:04 -0400
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-22 01:21 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-15 12:07 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-16 00:32 +0200
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-15 16:30 -0700
Re: Portable 16 bit binary integer write Keith Thompson <kst-u@mib.org> - 2016-09-15 18:35 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-15 22:00 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-15 22:17 -0700
Re: Portable 16 bit binary integer write Ian Collins <ian-news@hotmail.com> - 2016-09-16 18:12 +1200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-16 00:46 -0700
Re: Portable 16 bit binary integer write Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-16 10:23 +0100
Re: Portable 16 bit binary integer write BartC <bc@freeuk.com> - 2016-09-16 10:59 +0100
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-16 04:13 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-16 08:58 -0700
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-16 10:16 -0700
Re: Portable 16 bit binary integer write Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-16 09:11 -0700
Re: Portable 16 bit binary integer write David Brown <david.brown@hesbynett.no> - 2016-09-16 20:14 +0200
Re: Portable 16 bit binary integer write Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-16 20:37 -0700
Re: Portable 16 bit binary integer write supercat@casperkitty.com - 2016-09-13 07:47 -0700
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