Below is the code ive written just to count the characters typed in. I
assumed EOF is -1, so if i type -1 and then press enter shouldnt the
program end? It orks if i put something like 'q' in the while loop to
end the loop.
what is up?
<code>
#include <stdio.h>
void main() {
long nc;
nc = 0;
while (getchar() != 'EOF') {
++nc;
}
printf("%ld\n", nc);
}
</code>
thanks
Dave
Nov 13 '05
28  4606 
Dave <no*****@noemai l.com> wrote in message news:<bj******* ***@titan.btint ernet.com>... Below is the code ive written just to count the characters typed in. I
assumed EOF is -1, so if i type -1 and then press enter shouldnt the
program end?
When you type -1 at the command line, you're entering a string of
characters, not a single integral value. What getchar() sees in the
input stream is '-', '1', not -1.
Entering an EOF at the command line varies from system to system.
Some may not allow it at all. You're better off using a specific
character like 'q' for an explicit quit command.
You could try Ctrl-D or Ctrl-Z, but don't expect them to work
everywhere.
It orks if i put something like 'q' in the while loop to
end the loop.
what is up?
<code>
#include <stdio.h>
void main() {
int main (void) {
long nc;
nc = 0;
while (getchar() != 'EOF') {
Lose the quotes around EOF.
while (getchar() != EOF) { ++nc;
}
printf("%ld\n", nc);
}
</code>
thanks
Dave
amanayin <ng******@netsc ape.net> writes: Do you people know that code is taken from page 18
of The C programming language by kernigan & ritchie.
I am sure that K&R would not use 'EOF' to test for end-of-file,
because they know how to write C.
--
char a[]="\n .CJacehknorstu" ;int putchar(int);in t main(void){unsi gned long b[]
={0x67dffdff,0x 9aa9aa6a,0xa77f fda9,0x7da6aa6a ,0xa67f6aaa,0xa a9aa9f6,0x1f6}, *p=
b,x,i=24;for(;p +=!*p;*p/=4)switch(x=*p& 3)case 0:{return 0;for(p--;i--;i--)case
2:{i++;if(1)bre ak;else default:continu e;if(0)case 1:putchar(a[i&15]);break;}}}
amanayin <ng******@netsc ape.net> wrote: Do you people know that code is taken from page 18
of The C programming language by kernigan & ritchie.
Let's see...
OP> #include <stdio.h>
OP>
OP> void main() {
OP>
OP> long nc;
OP>
OP> nc = 0;
OP> while (getchar() != 'EOF') {
OP> ++nc;
OP> }
OP> printf("%ld\n", nc);
OP> }
K&R> #include <stdio.h>
K&R>
K&R> main()
K&R> {
K&R> long nc;
K&R>
K&R> nc = 0;
K&R> while (getchar() != EOF)
K&R> ++nc;
K&R> printf("%ld\n", nc);
K&R> }
Notice the two differences?
Hint: one invokes UB in OP's code.
Irrwahn
--
Close your eyes and press escape three times.
On Thu, 11 Sep 2003 16:27:04 UTC, Johan Aurér <au***@axis.com > wrote: On Thu, 11 Sep 2003, Irrwahn Grausewitz wrote:
Dave <no*****@noemai l.com> wrote:
long nc;
nc = 0;
while (getchar() != 'EOF') {
^^^^^
illegal character constant, just write EOF (it is defined in stdio.h)
It's not "illegal," just implementation-defined. In fact, 'EOF' might
even equal EOF if you're lucky. :-)
No, 'abc' or 'EOF' or 'BAD' is NOT a character. A character is a
single char, not a sequence of chars. A sequence of chars is known a
string, but a string must be in double quotes. So the compiler will
throw a diagnistic.
--
Tschau/Bye
Herbert
eComStation 1.1 Deutsch Beta ist verügbar
In article <wmzsGguTDN6N-pn2-1wd4V82b3Onx@mo on>,
The Real OS/2 Guy <os****@pc-rosenau.de> wrote: On Thu, 11 Sep 2003 16:27:04 UTC, Johan Aurér <au***@axis.com > wrote:
It's not "illegal," just implementation-defined. In fact, 'EOF' might
even equal EOF if you're lucky. :-)
ITYM "not lucky".
No, 'abc' or 'EOF' or 'BAD' is NOT a character. A character is a
single char, not a sequence of chars. A sequence of chars is known a
string, but a string must be in double quotes. So the compiler will
throw a diagnistic.
Quoth n869 (6.4.4.4):
--------
Description
[#2] An integer character constant is a sequence of one or
^^^^^^
more multibyte characters enclosed in single-quotes, as in
^^^^
'x' or 'ab'. A wide character constant is the same, except
prefixed by the letter L. With a few exceptions detailed
later, the elements of the sequence are any members of the
source character set; they are mapped in an implementation-
defined manner to members of the execution character set.
--------
So 'abc' is no less a character constant than 'a'. It may or may not
correspond to an acceptable char value, but it's perfectly acceptable as a
source code construct. (And, just for if you're going to try to nitpick
on the 'may not correspond to an acceptable value', I'll point out that
'a' isn't a "character" either, only a character constant whose value
(of integer type) corresponds to the appropriate character.)
dave
--
Dave Vandervies dj******@csclub .uwaterloo.ca
Fortunately programmers who actually use those anomalous cases are few,
and getting fewer every time we catch up to one.
--David Thompson in comp.lang.c
"The Real OS/2 Guy" <os****@pc-rosenau.de> wrote: On Thu, 11 Sep 2003 16:27:04 UTC, Johan Aurér <au***@axis.com > wrote:
On Thu, 11 Sep 2003, Irrwahn Grausewitz wrote:
> Dave <no*****@noemai l.com> wrote:
>
> >
> > long nc;
> >
> > nc = 0;
> > while (getchar() != 'EOF') {
> ^^^^^
> illegal character constant, just write EOF (it is defined in stdio.h)
It's not "illegal," just implementation-defined. In fact, 'EOF' might
even equal EOF if you're lucky. :-)
No, 'abc' or 'EOF' or 'BAD' is NOT a character.
It's not a character, it's a (integer) character constant with
implementation-defined value.
From WG14/N843, section 6.4.4.4:
[...]
[#2] An integer character constant is a sequence of one or
more multibyte characters enclosed in single-quotes, as in
'x' or 'ab'. A wide character constant is the same, except
prefixed by the letter L. With a few exceptions detailed
later, the elements of the sequence are any members of the
source character set; they are mapped in an implementation-
defined manner to members of the execution character set.
[...]
[#10] An integer character constant has type int. The value
of an integer character constant containing a single
character that maps to a member of the basic execution
character set is the numerical value of the representation
of the mapped character interpreted as an integer. The
value of an integer character constant containing more than
one character, or containing a character or escape sequence
not represented in the basic execution character set, is
implementation-defined. If an integer character constant
contains a single character or escape sequence, its value is
the one that results when an object with type char whose
value is that of the single character or escape sequence is
converted to type int.
<SNIP>
Irrwahn
--
I can't see it from here, but it looks good to me.
The Real OS/2 Guy wrote: On Thu, 11 Sep 2003 16:27:04 UTC, Johan Aurer <au***@axis.com > wrote:
It's not "illegal," just implementation-defined. In fact, 'EOF' might
even equal EOF if you're lucky. :-)
No, 'abc' or 'EOF' or 'BAD' is NOT a character.
It is, however, a character constant.
The Standard says: "An integer character constant is a sequence of one or
more multibyte characters enclosed in single-quotes, as in 'x' or 'ab'."
A character is a
single char,
So 'a' is not a character, then?
(Hint: 'a' is of type int, not char.)
--
Richard Heathfield : bi****@eton.pow ernet.co.uk
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton
The Real OS/2 Guy wrote: No, 'abc' or 'EOF' or 'BAD' is NOT a character. A character is a
single char, not a sequence of chars. A sequence of chars is known a
string, but a string must be in double quotes. So the compiler will
throw a diagnistic.
That must come as a shock to the guys who wrote the Standard:
[#2] An integer character constant is a sequence of one or
more multibyte characters enclosed in single-quotes, as in
'x' or 'ab'. A wide character constant is the same, except
prefixed by the letter L. With a few exceptions detailed
later, the elements of the sequence are any members of the
source character set; they are mapped in an implementation-
defined manner to members of the execution character set.
Brian Rodenborn
Irrwahn Grausewitz <ir*****@freene t.de> wrote in message news:<f3******* *************** **********@4ax. com>... "The Real OS/2 Guy" <os****@pc-rosenau.de> wrote:
On Thu, 11 Sep 2003 16:27:04 UTC, Johan Aurér <au***@axis.com > wrote:
On Thu, 11 Sep 2003, Irrwahn Grausewitz wrote:
> Dave <no*****@noemai l.com> wrote:
>
> >
> > long nc;
> >
> > nc = 0;
> > while (getchar() != 'EOF') {
> ^^^^^
> illegal character constant, just write EOF (it is defined in stdio.h)
It's not "illegal," just implementation-defined. In fact, 'EOF' might
even equal EOF if you're lucky. :-)
No, 'abc' or 'EOF' or 'BAD' is NOT a character.
It's not a character, it's a (integer) character constant with
implementation-defined value.
From WG14/N843, section 6.4.4.4:
[...]
[#2] An integer character constant is a sequence of one or
more multibyte characters enclosed in single-quotes, as in
'x' or 'ab'. A wide character constant is the same, except
prefixed by the letter L. With a few exceptions detailed
later, the elements of the sequence are any members of the
source character set; they are mapped in an implementation-
defined manner to members of the execution character set.
[...]
[#10] An integer character constant has type int. The value
of an integer character constant containing a single
character that maps to a member of the basic execution
character set is the numerical value of the representation
of the mapped character interpreted as an integer. The
value of an integer character constant containing more than
one character, or containing a character or escape sequence
not represented in the basic execution character set, is
implementation-defined. If an integer character constant
contains a single character or escape sequence, its value is
the one that results when an object with type char whose
value is that of the single character or escape sequence is
converted to type int.
<SNIP>
Irrwahn
When I use:
printf("%c\n", 'EOF');
It prints 'F', is it suppose to print that or am I invoking undefined behavior? ne*****@tokyo.c om (Mantorok Redgormor) wrote: Irrwahn Grausewitz <ir*****@freene t.de> wrote in message news:<f3******* *************** **********@4ax. com>..."The Real OS/2 Guy" <os****@pc-rosenau.de> wrote:
<SNIP>No, 'abc' or 'EOF' or 'BAD' is NOT a character.
It's not a character, it's a (integer) character constant with
implementatio n-defined value.
From WG14/N843, section 6.4.4.4:
[...]
[#2] An integer character constant is a sequence of one or
more multibyte characters enclosed in single-quotes, as in
'x' or 'ab'. A wide character constant is the same, except
prefixed by the letter L. With a few exceptions detailed
later, the elements of the sequence are any members of the
source character set; they are mapped in an implementation-
defined manner to members of the execution character set.
[...]
[#10] An integer character constant has type int. The value
of an integer character constant containing a single
character that maps to a member of the basic execution
character set is the numerical value of the representation
of the mapped character interpreted as an integer. The <
value of an integer character constant containing more than <
one character, or containing a character or escape sequence <
not represented in the basic execution character set, is <
implementation-defined. If an integer character constant <
contains a single character or escape sequence, its value is
the one that results when an object with type char whose
value is that of the single character or escape sequence is
converted to type int.
<SNIP>
When I use:
printf("%c\n", 'EOF');
It prints 'F', is it suppose to print that or am I invoking undefined behavior?
It prints whatever the implementor intended. I've marked the relevant
section in the quote above with '<'s. You are not invoking any UB, but
the result is implementation-defined. Thus, you cannot use it in
portable code, but as long as you stick to one implementation you may
use it, for whatever purpose. If you want to find out what the value
of such a multi-character-constant is like, you have to consult the
documentation that comes with your compiler.
Regards
Irrwahn
--
I can't see it from here, but it looks good to me. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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