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| From | Kaz Kylheku <kaz@kylheku.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. |
| Date | 2014-06-09 19:51 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <20140609121510.736@kylheku.com> (permalink) |
| References | <7128848c-179a-44d1-b2a8-cf8163bf6d2c@googlegroups.com> |
On 2014-06-09, Christos Kokaliaris <chrisk.msor@gmail.com> wrote:
> Greetings everybody,
>
> I am a Mathematics graduate and I need C in order to integrate it with R and
> other languages I use for statistics and simulation. I took C when
> undergraduate but it wasn't enough. Recently I decided to study analytically
> the classic book and solve every single exercise. After comparing my own code
> with the already suggested in the archives of clc-wiki, I thought of posting
> my solutions.
>
> Criticism and suggestions on the quality of the solutions I suggest are much needed and most welcome.
>
> Thank you for reading.
>
> // ex1-9
> #include <stdio.h>
>
> /* copy input into output, replacing
> one or more blanks by a single blank */
> main()
> {
> int c, nb=0;
>
Do not post tabs in Usenet; the indentation will get screwed up
when reply quotes are added, and as more levels of reply quotes
are piled on.
> while ((c=getchar()) != EOF) {
> /* if char is blank increase counter else reset counter.
> this notation will be mentioned later in the book
> (T) ? A : B; if TRUE then A else B */
> (c == ' ') ? (++nb) : (nb = 0);
While this is technically okay, and even laudable in some ways, most
"blub programmers" (i.e. the majority of your C programming colleagues) will
frown on a ternary conditional having its value discarded and being used as a
statement.
>
> //ex1-12
> #include <stdio.h>
>
> #define IN 1
> #define OUT 0
>
> // print input one word per line
> main()
> {
> int c, state;
> // start without a word
> state = OUT;
This could be:
int c;
enum { OUT, IN } state = out;
Don't use preprocessor symbols without a good reason, and restrict
the scope of identifiers to where they are actually used.
If you use an enum, then values of the state variable will probably be nicely
shown as OUT and IN in your debugger, too.
>
> while ((c = getchar()) != EOF) {
> // if the char is not blank, tab, newline
> if (c != ' ' && c != '\t' && c != '\n') {
> // inside a word
> state = IN;
> putchar(c);
> }
> // otherwise char is blank, tab, newline, word ended
> else if (state == IN) {
> state = OUT;
> putchar('\n');
> }
> }
> }
Multiple comparisons of integer variables are often more effectively expressed
using switch:
switch (ch) {
case ' ': case '\t': case '\n':
if (state == IN) {
state = OUT;
putchar('\n');
}
break;
default:
state = IN;
putchar(c);
break;
}
The program has the following flaw: what if the input happens to ends in the
middle of a word? That will not happen for a well-formed text stream; every
line is newline terminated. Still, in the situation of a malformed text stream,
it might be nice to do the putchar('\n') so that the output is a well-formed
text stream.
/* after loop */
if (state == IN) /* input ended/errored within word */
putchar('\n');
In general, when you write state machines like this, they often have final
clean-up actions to be done when they terminate. This is because EOF was
treated as an out-of-band signal rather than one of the symbols from
the input stream.
For that reason, it often behooves you to include EOF as a symbol.
We can incorporate that into the state machine like this:
do{
switch ((c = getchar())) {
case EOF:
case ' ': case '\t': case '\n':
if (state == IN) {
state = OUT;
putchar('\n');
}
break;
default:
state = IN;
putchar(c);
break;
}
} while (c != EOF);
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C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Christos Kokaliaris <chrisk.msor@gmail.com> - 2014-06-09 12:12 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Christos Kokaliaris <chrisk.msor@gmail.com> - 2014-06-09 12:41 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Barry Schwarz <schwarzb@dqel.com> - 2014-06-09 13:16 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-12 09:08 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. raltbos@xs4all.nl (Richard Bos) - 2014-06-12 16:35 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-13 07:27 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Jorgen Grahn <grahn+nntp@snipabacken.se> - 2014-06-14 00:13 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-16 07:07 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Jorgen Grahn <grahn+nntp@snipabacken.se> - 2014-06-16 20:04 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-17 08:56 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. raltbos@xs4all.nl (Richard Bos) - 2014-06-16 12:53 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-16 08:00 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Kaz Kylheku <kaz@kylheku.com> - 2014-06-16 16:01 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-17 08:24 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. raltbos@xs4all.nl (Richard Bos) - 2014-06-18 10:50 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-26 19:07 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Kaz Kylheku <kaz@kylheku.com> - 2014-06-09 19:51 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Jorgen Grahn <grahn+nntp@snipabacken.se> - 2014-06-09 20:15 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Christos Kokaliaris <chrisk.msor@gmail.com> - 2014-06-09 13:21 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Keith Thompson <kst-u@mib.org> - 2014-06-09 13:39 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-06-09 21:23 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Kaz Kylheku <kaz@kylheku.com> - 2014-06-09 21:43 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-06-10 00:17 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. "BartC" <bc@freeuk.com> - 2014-06-10 11:13 +0100
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Keith Thompson <kst-u@mib.org> - 2014-06-10 07:38 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. raltbos@xs4all.nl (Richard Bos) - 2014-06-10 10:23 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Dr Nick <nospam-4@temporary-address.org.uk> - 2014-06-10 18:55 +0100
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Keith Thompson <kst-u@mib.org> - 2014-06-09 15:14 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-06-10 00:21 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. James Kuyper <jameskuyper@verizon.net> - 2014-06-09 21:37 -0400
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Keith Thompson <kst-u@mib.org> - 2014-06-10 07:45 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-11 01:32 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Cal Dershowitz <Cal@example.invalid> - 2014-06-09 23:14 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. raltbos@xs4all.nl (Richard Bos) - 2014-06-10 10:14 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2014-06-10 22:06 +0300
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. raltbos@xs4all.nl (Richard Bos) - 2014-06-11 16:16 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Kaz Kylheku <kaz@kylheku.com> - 2014-06-11 16:47 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2014-06-11 20:50 +0300
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. raltbos@xs4all.nl (Richard Bos) - 2014-06-11 16:16 +0000
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2014-06-10 08:23 -0600
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Keith Thompson <kst-u@mib.org> - 2014-06-10 10:12 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-12 08:39 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Robert Wessel <robertwessel2@yahoo.com> - 2014-06-12 12:30 -0500
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Seungbeom Kim <musiphil@bawi.org> - 2014-06-10 23:34 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-11 00:35 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Keith Thompson <kst-u@mib.org> - 2014-06-11 08:35 -0700
Re: C Programming Language 2nd Ed, Exercise 1.9 and 1.12, Solution suggestion. Kaz Kylheku <kaz@kylheku.com> - 2014-06-11 15:49 +0000
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