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Groups > comp.lang.c > #151304
| Subject | Re: C String terminator |
|---|---|
| Newsgroups | comp.lang.c |
| References | (14 earlier) <4b9b90a0-0393-41de-8857-1f8e379e4d79@googlegroups.com> <cc8db103-9023-4756-b19d-158077333c30@googlegroups.com> <2IokG.1296436$ek.27835@fx48.iad> <87h7xpn44g.fsf@bsb.me.uk> <c6ecfa15-23a6-419a-8bbc-e5f9175373b4@googlegroups.com> |
| From | Richard Damon <Richard@Damon-Family.org> |
| Message-ID | <5k%kG.2$th5.0@fx14.iad> (permalink) |
| Organization | Forte - www.forteinc.com |
| Date | 2020-04-13 11:13 -0400 |
On 4/12/20 7:39 AM, Malcolm McLean wrote:
> On Saturday, 11 April 2020 21:45:30 UTC+1, Ben Bacarisse wrote:
>> Richard Damon <Richard@Damon-Family.org> writes:
>>
>>> On 4/10/20 2:38 PM, Malcolm McLean wrote:
>>>> On Friday, 10 April 2020 15:13:20 UTC+1, 嘱 Tiib wrote:
>>>>>
>>>>> I was asking because you were seemingly claiming that when
>>>>> some used bits are originating from memory mapped input and/or
>>>>> some altered bits go into memory mapped output then it somehow
>>>>> does not matter because the code is likely platform specific.
>>>>> However purity and portability seem to be orthogonal properties
>>>>> of code and correlation seems incidental.
>>>>>
>>>> Pure functions can always be written portably.
>>>
>>> Disagree here. The ONLY way you can make such a claim is to restrict
>>> your machine definition to something that isn't efficient. Either you
>>> need to define that all math is to be done in infinite precision
>>> arithmetic (which is inefficient on most machines), has a language
>>> defined precision (sort of like what Java does so that it is inefficient
>>> on any machine that doesn't well match the language specification) or
>>> you get non-portable answers. C was designed for efficiency over
>>> portability, which is one reason it did succeed in its designed market.
>>
>> I was debating whether to make this point as well. MM is a broad-brush
>> kind of person and I am sure there is some meaning (possibly along the
>> lines you paint here) that is what was really meant. Anyway, for what
>> it's worth, my example was going to be
>>
>> unsigned long long bit_set(void)
>> {
>> return 0x800008000200000020000000800A20AC;
>> }
>>
>> where the author clearly knew that unsigned long long was 128 bits wide.
>>
>> This function can't be written portably (in the usual sense of the word)
>> because not all implementations have an 128-bit unsigned type. The
>> whole program would need to be re-engineered (quite possible including
>> some of the I/O library) to use an invented fake 128-bit integer type.
>> And even that counts as "portable", it's likely that a total re-design
>> of affected parts would be an better option.
>>
>> The fact that this function is pure is, to put is mildly, secondary to
>> the fact that it is very much not portable.
>>
> A function maps bits on entry to bits on exit, and if you want to be
> 100% portable you have to specify it in terms of bits. So yes, you
> need to fake up a 128 bit type if you need 128 bit computations. But
> you can do that.
> Instead of saying "this function must return a C unsigned long that
> holds the value 0x800008000200000020000000800A20AC, which is clearly
> impossible to achieve portably, we need to say
> "this function must map the unit set (an empty list of bits in), to
> the set of bits that represent values, choosing the member that
> represents the value 0x800008000200000020000000800A20AC".
>
> You then have to provide "the set of bits that represent values", which
> depends on the rest of the program.
>
> There's the human-meaningful function you are trying to model, then
> there's the C type. Sometimes, though rarely, the C types won't be
> up to the task of modelling the human-meaningful function, so you
> have to drop down to bits.
>
> To give another example, consider the fucntion "cosine". We could say
> the human meaningful function is "this function shall a reasonable
> approximation to the cosine of theta, as long as theta is reasonably
> close to the range +/- 2 * PI". Or we could say, "this function shall
> return the cosine of theta, adhering exactly to important body standard
> this and that".
> You can reasonably want either, but if the higher ups demand the second,
> we have a portablity headache. However that won't daunt us. We'll just
> download some floating point routines from github, and build the
> function on top of integer operations.
>
So I guess this means that C can't have functions, since C has no
totally portable way of defining inputs and outputs in terms of 'bits'.
The closest you can get with this would be arrays of unsigned chars,
which even that is technically not portable in C since you have some
machines where CHAR_BITS != 8. Also most of the standard library are not
functiona since it defines inputs and outputs in terms of things that
aren't fixed in size. (maybe some of the string functions are if you are
willing to restrict yourself to machines with CHAR_BITS = 8).
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Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-16 02:25 -0800
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-02-16 14:24 -0800
Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-22 08:13 -0800
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-02-22 09:05 -0800
Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-03-27 19:58 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-03-27 23:26 -0700
Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-02 09:21 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-02 09:54 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-02 11:17 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-02 13:12 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-02 13:28 -0700
Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-02 19:17 -0700
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-03 09:47 +0200
Re: C String terminator already5chosen@yahoo.com - 2020-04-03 08:03 -0700
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-03 17:34 +0200
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-03 12:39 -0400
Re: C String terminator Bart <bc@freeuk.com> - 2020-04-03 18:05 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-03 10:18 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-03 22:13 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-03 14:36 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-03 16:18 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-04 01:43 -0700
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-04 18:23 +0200
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-04 11:18 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-04 13:02 -0700
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-05 21:54 +0200
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-05 13:59 -0700
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-06 09:07 +0200
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-06 02:25 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-06 11:43 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-06 03:56 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-06 16:34 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-06 10:30 -0700
Re: C String terminator richard@cogsci.ed.ac.uk (Richard Tobin) - 2020-04-06 17:50 +0000
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-06 11:31 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-06 12:04 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-06 21:51 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-06 14:34 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-06 14:39 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-06 14:52 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-06 15:31 -0700
Re: C String terminator jameskuyper@stellarscience.com - 2020-04-06 16:05 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-07 03:08 +0100
Re: C String terminator Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2020-04-06 21:12 -0600
Re: C String terminator scott@slp53.sl.home (Scott Lurndal) - 2020-04-07 16:55 +0000
Re: C String terminator Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2020-04-07 11:05 -0600
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-07 20:39 +0200
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 11:48 -0700
Re: C String terminator Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2020-04-07 21:21 -0600
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-07 20:40 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-08 01:41 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-08 07:40 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-08 08:16 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-08 09:17 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-08 09:46 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-08 10:37 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-08 10:48 -0700
Re: C String terminator Richard Damon <Richard@Damon-Family.org> - 2020-04-08 14:07 -0400
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-08 11:29 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-08 16:46 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-09 01:57 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-09 08:42 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-09 08:56 -0700
Re: C String terminator Richard Damon <Richard@Damon-Family.org> - 2020-04-09 12:42 -0400
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-09 10:12 -0700
Re: C String terminator Richard Damon <Richard@Damon-Family.org> - 2020-04-09 15:51 -0400
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-09 13:02 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-09 13:06 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-09 14:49 -0700
Re: C String terminator Richard Damon <Richard@Damon-Family.org> - 2020-04-09 19:05 -0400
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-10 02:25 -0700
Re: C String terminator Öö Tiib <ootiib@hot.ee> - 2020-04-10 04:38 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-10 05:21 -0700
Re: C String terminator Öö Tiib <ootiib@hot.ee> - 2020-04-10 07:13 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-10 11:38 -0700
Re: C String terminator Ike Naar <ike@sdf.lonestar.org> - 2020-04-11 17:38 +0000
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-11 15:04 -0700
Re: C String terminator Richard Damon <Richard@Damon-Family.org> - 2020-04-11 15:16 -0400
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-11 21:45 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-12 04:39 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-12 21:34 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-12 14:38 -0700
Re: C String terminator Richard Damon <Richard@Damon-Family.org> - 2020-04-13 11:13 -0400
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-13 08:24 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-11 15:08 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-09 09:53 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-07 14:35 -0400
Re: C String terminator Öö Tiib <ootiib@hot.ee> - 2020-04-06 21:04 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 01:16 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-07 02:08 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 02:19 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-07 08:42 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 10:39 -0700
Re: C String terminator scott@slp53.sl.home (Scott Lurndal) - 2020-04-07 17:45 +0000
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-07 14:40 -0400
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-07 11:03 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 11:14 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-07 12:19 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-07 12:02 +0100
Re: C String terminator Öö Tiib <ootiib@hot.ee> - 2020-04-07 06:27 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 07:44 -0700
Re: C String terminator Öö Tiib <ootiib@hot.ee> - 2020-04-07 08:30 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 00:27 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-07 12:50 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-07 05:25 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-07 23:52 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-08 03:15 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-08 21:28 +0100
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-08 15:40 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-09 00:31 +0100
Re: C String terminator Ike Naar <ike@sdf.lonestar.org> - 2020-04-07 21:40 +0000
Re: C String terminator luser droog <luser.droog@gmail.com> - 2020-04-06 09:41 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-06 12:46 -0700
Re: C String terminator Guillaume <message@bottle.org> - 2020-04-07 17:17 +0200
Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-09 07:23 -0700
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-04 22:32 +0100
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-03 21:59 +0200
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-03 23:48 -0400
Jared Kushner would be proud... (Was: C String terminator) gazelle@shell.xmission.com (Kenny McCormack) - 2020-04-04 09:00 +0000
Re: Jared Kushner would be proud... (Was: C String terminator) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-04 02:45 -0700
Re: Jared Kushner would be proud... (Was: C String terminator) Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-04-04 10:24 +0000
Re: Jared Kushner would be proud... (Was: C String terminator) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-04 03:55 -0700
Re: Jared Kushner would be proud... Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-04 13:27 -0700
Re: Jared Kushner would be proud... Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-04 13:52 -0700
Re: Jared Kushner would be proud... Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-04 14:12 -0700
Re: Jared Kushner would be proud... Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-04 15:12 -0700
Re: Jared Kushner would be proud... Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-04 15:03 -0700
Re: Jared Kushner would be proud... Richard Damon <Richard@Damon-Family.org> - 2020-04-04 18:46 -0400
Re: Jared Kushner would be proud... Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-05 01:53 -0700
Re: Jared Kushner would be proud... Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-05 02:33 -0700
Re: Jared Kushner would be proud... Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-05 06:43 -0700
Re: Jared Kushner would be proud... (Was: C String terminator) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-04 19:48 -0700
Re: Jared Kushner would be proud... (Was: C String terminator) James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-04 06:37 -0700
Re: C String terminator David Brown <david.brown@hesbynett.no> - 2020-04-04 18:36 +0200
Re: C String terminator dave_thompson_2@comcast.net - 2020-05-02 15:13 -0400
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-03 09:41 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-03 10:33 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-03 11:14 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-03 11:34 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-03 14:48 -0400
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-03 12:10 -0700
Re: C String terminator Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-03 13:24 -0700
Re: C String terminator James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-03 23:59 -0400
Re: C String terminator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-04-03 22:05 +0100
Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-04 20:34 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-05 02:05 -0700
Re: C String terminator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-09 07:35 -0700
Re: C String terminator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-09 07:38 -0700
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