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Groups > comp.lang.c > #151112

Re: C String terminator

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: C String terminator
Date 2020-04-06 09:07 +0200
Organization A noiseless patient Spider
Message-ID <r6ekep$sbj$1@dont-email.me> (permalink)
References (20 earlier) <13e81aac-375b-45ba-9261-8153c406368c@googlegroups.com> <r6ac9d$5vi$1@dont-email.me> <09e137e8-7bf0-4b5b-b098-52f31bfdfe64@googlegroups.com> <r6dd1a$a1n$1@dont-email.me> <bb8f76d2-f69e-480e-9625-f31bcf8f1f3c@googlegroups.com>

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On 05/04/2020 22:59, Malcolm McLean wrote:
> On Sunday, 5 April 2020 20:54:35 UTC+1, David Brown  wrote:
>> On 04/04/2020 20:18, Malcolm McLean wrote:
>>
>> Correct - "rand()" as defined by the C standards cannot be a pure
>> function, as it holds state.  But "pure function" remains a reasonable,
>> though not perfect, term for a function whose result is solely dependent
>> on its input arguments.
>>
>> Only you can really say what you mean by "Malcolm-function", and I'm not
>> convinced your definition has been consistent every time it comes up.
>> But by your current definition, pure functions are a subset of Malcolm
>> functions.
>>
> I didn't invent the term "Malcolm function". I used the term "function"
> in one of its accepted meanings. 

A meaning accepted by /you/, but not by others in this group.  Quite 
possibly you use it in a way that is accepted in some other specific 
context, but different from its use in C.

> A mapping of sets, of bits since we
> are talkng about digital computers. If you don't allow globals and you
> don't allow writes through pointers, so every function call is of the
> form
> 
> returnbits = functioncall(argumentbits)
> 
> then this becomes obvious. But C isn't that language.

I would say that this does not match your last Malcolm-function 
definition, because it does not allow something like "rand()" with 
static data.  What you are talking about here is nothing more than a 
mathematical function with a particular type of domain.  The word 
"function" has an accepted meaning in mathematics, but this is C 
programming, not mathematics.

> 
>>> a [piece of code which calculates] a relationship between two sets [of
>>> bits] in which each part of the first set is connected with just one
>>> member of the second set in number pairs [Cambridge dictionary]
>>>
>>
>> Why would you think an English language dictionary definition would be
>> relevant here?  (That's a rhetorical question - we all know that it is
>> not relevant.)
>>
> The concept of a function as a mapping of a first set to a second
> set is important.

It is important - in mathematics.  This is not a mathematics group. 
(And mathematicians would be unlikely to look at a language dictionary 
for a meaning of their terms.)

>>
>>> It is crashingly simple. Either it does IO or not. If you do IO, you
>>> are doing something, you are not (just) calculating something. So
>>> you are a "procedure".
>>>    
>>
>> You can't make such a distinction, because there is no clear separation
>> of whether code performs IO or does not.  A piece of code may sometimes
>> perform an external IO operation and sometimes not, depending its
>> arguments - does it then change between being a Malcolm-function and a
>> Malcolm-procedure?  A piece of code may change a variable in memory that
>> is not displayed in normal use, but is logged in debug mode - does the
>> mode of compilation or execution change the nature of the code?  What if
>> the function can be compiled with or without logging enabled?  You are
>> making an artificial distinction where none exists, and claiming it to
>> be a distinguishing factor in dividing types of code where there is no
>> benefit.
>>
> OK, so genrally there is no problem. The "function" printf() is
> desinged to send characters to a device attached to standard output.
> The function sqrt() makes a one to one mapping between its argument
> and return value (and errno, which is why we can't use the term "pure
> fucntion"). Go through the standard library, and everyone will
> probably agree which are the IO procedures and which are the non
> IO functions.
> 
> But what if code is instrumented for debug. What if stdout is reattached
> to a memory buffer? What if a fucntion is passed a buffer which happens
> to be memory mapped to a disply device? We can make things more complicated.
> 
> But let's not distract ouselves from the central idea. If you do IO,
> you are dependent on the machinery being attached to the computer.
> If you do bit shuffling, you are not.

It is not a matter of "distracting ourselves".  You apparently agree 
there is no clear distinction between functions that perform IO and 
functions that do not.  It doesn't matter if 90% of functions can be 
clearly categorised, or 99.9%, or 99.9999%.  Attention to corner cases 
is how you do correct programming (and mathematics, for that matter) - 
it's the difference between a program that "works okay when I tested it" 
and "is known to be correct".

Given a C function "foo", you can't be sure it can is a Malcolm-function 
or a Malcolm-procedure, and you can't be sure if its status is constant 
in different circumstances of compilation or running.  You certainly 
have no idea based only on its declaration.  It is therefore a pointless 
distinction (at least in C).

Surely that can be the end of this pointless discussion, and hopefully 
the last time we see the terms "Malcolm-function" or "Malcolm-procedure"?

<snip>

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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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