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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Reading beyond the end of file |
| Date | 2015-09-11 14:36 -0700 |
| Organization | None to speak of |
| Message-ID | <ln613gmyel.fsf@kst-u.example.com> (permalink) |
| References | (1 earlier) <mqts2p$js0$1@dont-email.me> <lnk2st4bg0.fsf@kst-u.example.com> <kfnbndfql81.fsf@x-alumni2.alumni.caltech.edu> <lnsi6rt7id.fsf@kst-u.example.com> <kfnmvwskhqm.fsf@x-alumni2.alumni.caltech.edu> |
Tim Rentsch <txr@alumni.caltech.edu> writes:
> Keith Thompson <kst-u@mib.org> writes:
>> Tim Rentsch <txr@alumni.caltech.edu> writes:
>>> Keith Thompson <kst-u@mib.org> writes:
[...]
>>>> It never makes sense to store the value EOF in a char, signed char,
>>>> or unsigned char object. It's intended as an in-band signal,
>>>> distinct from any valid input character. [snip]
>>>
>>> Presumably you meant to say out-of-band rather than in-band.
>>
>> No, I meant to say in-band. It's possible I misused the term, but I
>> don't think so.
>>
>> Calling getchar() repeatedly gives you a sequence of int values. Most
>> of those values are going to represent character values in the range
>> 0..UCHAR_MAX. The value EOF in the same sequence does not represent a
>> character value.
>
> Which term applies depends on what is considered "the band". I
> think of getchar() as returning a character - the type is int,
> but what the value represents is a character. I think most C
> developers think of getchar() as returning a character. From
> this perspective, the value EOF, which is negative whereas all
> character values are non-negative (with the usual assumption that
> UCHAR_MAX <= INT_MAX), qualifies as an "out-of-band" value. To
> say this another way, there is no character that can be written
> to a file which when read back (under the same assumption as
> before) would give EOF.
>
> I agree of course that getchar() returns int values, but it does
> that precisely so that it can accommodate an extra value (EOF)
> that corresponds to no character. The range of the type is not
> the same as the range of the values.
>
> Let me add that there is nothing logically wrong with thinking
> of "the band" as being all character values plus EOF, or as
> being all int values even though most of the negative ones are
> never returned. I just think that doesn't correspond to most
> developers' mental model for what getchar() is used for.
Thinking of getchar() as a function that returns a character is what
leads a lot of (mostly beginning) programmers to incorrectly assign its
return value to a char object. (I'm sure you don't make that mistake
yourself.)
It seems to be that getchar()'s behavior matches the idea of in-band
signalling almost perfectly.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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Reading beyond the end of file janus <emekamicro@gmail.com> - 2015-08-17 16:24 -0700
Re: Reading beyond the end of file Bartc <bc@freeuk.com> - 2015-08-18 00:53 +0100
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-08-17 18:44 -0700
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 14:41 -0700
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-09-06 17:09 -0700
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-11 10:06 -0700
Re: Reading beyond the end of file Geoff <geoff@invalid.invalid> - 2015-09-11 12:41 -0700
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-26 14:24 -0700
Re: Reading beyond the end of file Geoff <geoff@invalid.invalid> - 2015-09-26 21:49 -0700
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 13:57 -0700
Re: Reading beyond the end of file Geoff <geoff@invalid.invalid> - 2015-10-01 17:22 -0700
Re: Reading beyond the end of file raltbos@xs4all.nl (Richard Bos) - 2015-10-02 13:05 +0000
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 17:56 -0700
Re: Reading beyond the end of file Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-09-11 13:55 -0600
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-26 14:14 -0700
Re: Reading beyond the end of file Siri Cruz <chine.bleu@yahoo.com> - 2015-09-26 14:43 -0700
Re: Reading beyond the end of file Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-09-26 17:57 -0400
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 14:01 -0700
Re: Reading beyond the end of file Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-09-26 22:18 -0600
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 12:58 -0700
Re: Reading beyond the end of file Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-10-01 15:08 -0600
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 18:03 -0700
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 04:02 +0000
Re: Reading beyond the end of file raltbos@xs4all.nl (Richard Bos) - 2015-10-02 13:11 +0000
Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-02 09:31 -0700
Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-03 16:07 -0400
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 19:06 -0700
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-09-11 14:36 -0700
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-26 14:05 -0700
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-09-26 18:53 -0700
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 13:49 -0700
Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-01 20:23 -0400
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-02 06:14 +0000
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 19:03 -0700
Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-04 22:55 -0400
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 04:27 +0000
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-04 22:21 -0700
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 09:53 +0000
Re: Reading beyond the end of file James Kuyper <jameskuyper@verizon.net> - 2015-10-05 13:15 -0400
Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-05 10:25 -0700
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:30 +0000
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:27 +0000
Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-05 10:17 -0700
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-05 11:59 -0700
Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-05 13:44 -0700
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:58 +0000
Ones' complement subtraction supercat@casperkitty.com - 2015-10-05 15:28 -0700
Re: Ones' complement subtraction glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 02:14 +0000
Re: Ones' complement subtraction supercat@casperkitty.com - 2015-10-06 08:48 -0700
Re: Ones' complement subtraction glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 20:55 +0000
Re: Ones' complement subtraction supercat@casperkitty.com - 2015-10-06 14:41 -0700
Re: Ones' complement subtraction glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-07 00:14 +0000
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-05 15:24 -0700
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:39 +0000
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-05 15:31 -0700
Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 03:04 +0000
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-06 08:55 -0700
Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-06 11:44 -0700
Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-05 23:16 -0400
Re: Reading beyond the end of file James Kuyper <jameskuyper@verizon.net> - 2015-10-06 10:29 -0400
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-06 08:56 -0700
Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-06 23:13 -0400
Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-06 22:01 -0700
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-07 08:43 -0700
Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-07 10:02 -0700
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-07 13:08 -0700
Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-07 22:03 -0400
Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-05 01:47 -0700
Re: Reading beyond the end of file James Kuyper <jameskuyper@verizon.net> - 2015-08-17 20:10 -0400
Re: Reading beyond the end of file janus <emekamicro@gmail.com> - 2015-08-18 00:54 -0700
Re: Reading beyond the end of file janus <emekamicro@gmail.com> - 2015-08-18 01:43 -0700
Re: Reading beyond the end of file James Kuyper <jameskuyper@verizon.net> - 2015-08-18 10:18 -0400
Re: Reading beyond the end of file Barry Schwarz <schwarzb@dqel.com> - 2015-08-18 09:18 -0700
Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-08-18 11:17 -0700
Re: Reading beyond the end of file Barry Schwarz <schwarzb@dqel.com> - 2015-08-18 13:24 -0700
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