What is the scope of this while loop?

[JS]

#include <stdio.h>

main(){

int c, i, nwhite, nother;
int ndigit[10];

nwhite = nother = 0;

for (i = 0; i < 10; ++i)
ndigit = 0;

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
++ndigit[c-'0'];
else
if (c == ' ' || c == '\n' || c == '\t')
++nwhite;
else
++nother;

printf("digits =");
for (i = 0; i < 10; ++i)
printf(" %d", ndigit);

printf(", white space = %d, other = %d\n",
nwhite, nother);

}

Where does the above while loop end?? For some reason all the examples I
have read with C code there is no brackets to confine the while loop (like
in Java).

JS

 

[Mike Deskevich]

here's the bracketed version. i'm pretty sure i got it right, but you
better double check the output of both versions to make sure they
match.



#include <stdio.h>

main()
{
int c, i, nwhite, nother;
int ndigit[10];

nwhite = nother = 0;

for (i = 0; i < 10; ++i)
{
ndigit = 0;
}

while ((c = getchar()) != EOF)
{
if (c >= '0' && c <= '9')
{
++ndigit[c-'0'];
}
else
{
if (c == ' ' || c == '\n' || c == '\t')
{
++nwhite;
}
else
{
++nother;
}
}
}

printf("digits =");

for (i = 0; i < 10; ++i)
{
printf(" %d", ndigit);
}

printf(", white space = %d, other = %d\n",
nwhite, nother);

}

 

[Lew Pitcher]

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#include <stdio.h>

main(){

int c, i, nwhite, nother;
int ndigit[10];

nwhite = nother = 0;

for (i = 0; i < 10; ++i)
ndigit = 0;

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
++ndigit[c-'0'];
else
if (c == ' ' || c == '\n' || c == '\t')
++nwhite;
else
++nother;

printf("digits =");
for (i = 0; i < 10; ++i)
printf(" %d", ndigit);

printf(", white space = %d, other = %d\n",
nwhite, nother);

}

Where does the above while loop end??

In C, a while() statement consists of three parts:
1) the 'while' keyword,
2) a condition, enclosed in parenthesis, and
3) a single statement to be executed if the condition tests true

In C, a series of statements, enclosed in brace brackets, is considered to be a
single statement.

Thus:
while (1) printf("Continious loop\n");
and
while (1) { printf("Continious loop\n");
are equivalent.

So, to answer your question, the while() statement in your example code extends
from the while() to the ++nother;

Or in other words, the following is a whole while() statement.

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
++ndigit[c-'0'];
else
if (c == ' ' || c == '\n' || c == '\t')
++nwhite;
else
++nother;

For some reason all the examples I
have read with C code there is no brackets to confine the while loop (like
in Java).

The implication is that Java requires that the body of a while loop be enclosed
in brace brackets. So?? What's Java got to do with it? Different languages have
different rules.

- --
Lew Pitcher
IT Specialist, Enterprise Data Systems,
Enterprise Technology Solutions, TD Bank Financial Group

(Opinions expressed are my own, not my employers')
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[Lew Pitcher]

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Lew Pitcher wrote:
[snip]

In C, a while() statement consists of three parts:
1) the 'while' keyword,
2) a condition, enclosed in parenthesis, and
3) a single statement to be executed if the condition tests true

In C, a series of statements, enclosed in brace brackets, is considered to be a
single statement.

Thus:
while (1) printf("Continious loop\n");
and
while (1) { printf("Continious loop\n");

Oops. Correction
while (1) { printf("Continious loop\n"); }

are equivalent.

[snip]

- --
Lew Pitcher
IT Specialist, Enterprise Data Systems,
Enterprise Technology Solutions, TD Bank Financial Group

(Opinions expressed are my own, not my employers')
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[Vig]

--
--
Vig

#include <stdio.h>

main(){

int c, i, nwhite, nother;
int ndigit[10];

nwhite = nother = 0;

for (i = 0; i < 10; ++i)
ndigit = 0;

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
++ndigit[c-'0'];
else
if (c == ' ' || c == '\n' || c == '\t')
++nwhite;
else
++nother;

printf("digits =");
for (i = 0; i < 10; ++i)
printf(" %d", ndigit);

printf(", white space = %d, other = %d\n",
nwhite, nother);

}

Where does the above while loop end?? For some reason all the examples I
have read with C code there is no brackets to confine the while loop (like
in Java).

I believe the while loop extends till the line just prior to the first
printf statement. This is because only the line immediately after a while
loop is in its scope. However, the if statemnt's scope extends back to the
while loop.

 

[Keith Thompson]

#include <stdio.h>

main(){

int c, i, nwhite, nother;
int ndigit[10];

nwhite = nother = 0;

for (i = 0; i < 10; ++i)
ndigit = 0;

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
++ndigit[c-'0'];
else
if (c == ' ' || c == '\n' || c == '\t')
++nwhite;
else
++nother;

printf("digits =");
for (i = 0; i < 10; ++i)
printf(" %d", ndigit);

printf(", white space = %d, other = %d\n",
nwhite, nother);

}

Where does the above while loop end?? For some reason all the examples I
have read with C code there is no brackets to confine the while loop (like
in Java).

A while() always controls a single statement. Typically that single
statement is a compound statement, which is delimited by '{' and '}',
but it can be any statement.

In this case, the single statement is the if-else statement consisting
of the 7 lines following the while().

Note that the indentation on the last two of those lines is incorrect;
the "else" should be directly under the "if", and the "++nother;"
should be directly under the "++nwhite;". (This isn't incorrect in
the sense that a compiler is going to complain about it, but it's
misleading.)

Personally, I always use braces around sub-statements like this (a
habit I picked up from Perl, which requires them). Mike Deskevich's
fully braced version of your program appears to be correct.

 

[CBFalconer]

#include <stdio.h>

main(){

int c, i, nwhite, nother;
int ndigit[10];

nwhite = nother = 0;

for (i = 0; i < 10; ++i)
ndigit = 0;

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
++ndigit[c-'0'];
else
if (c == ' ' || c == '\n' || c == '\t')
++nwhite;
else
++nother;

printf("digits =");
for (i = 0; i < 10; ++i)
printf(" %d", ndigit);

printf(", white space = %d, other = %d\n",
nwhite, nother);

}

Where does the above while loop end?? For some reason all the
examples I have read with C code there is no brackets to confine
the while loop (like in Java).

It ends after one statement, which may be a compound statement,
effected via {}. Better indentation and formatting will show
things up clearly, as in:

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9') ++ndigit[c-'0'];
else if (c == ' ' || c == '\n' || c == '\t') ++nwhite;
else ++nother;

I don't believe in extra braces when the complete condition/action
can be specified on one line of reasonable length.

 

[Peter Nilsson]

... Better indentation and formatting will show
things up clearly, as in:
.
while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9') ++ndigit[c-'0'];
else if (c == ' ' || c == '\n' || c == '\t') ++nwhite;
else ++nother;
.
I don't believe in extra braces when the complete condition/action
can be specified on one line of reasonable length.

Does that mean you're writing...

while (blah) continue;

....instead of...

while (blah)
{
continue;
}

....these days!

 

[pete]

... Better indentation and formatting will show
things up clearly, as in:
.
while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9') ++ndigit[c-'0'];
else if (c == ' ' || c == '\n' || c == '\t') ++nwhite;
else ++nother;
.
I don't believe in extra braces when the complete condition/action
can be specified on one line of reasonable length.

Does that mean you're writing...

while (blah) continue;

...instead of...

while (blah)
{
continue;
}

...these days!

I prefer compound statements with all ifs and loops.
It makes reading simpler.

 

[CBFalconer]

... Better indentation and formatting will show
things up clearly, as in:
.
while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9') ++ndigit[c-'0'];
else if (c == ' ' || c == '\n' || c == '\t') ++nwhite;
else ++nother;
.
I don't believe in extra braces when the complete condition/action
can be specified on one line of reasonable length.

Does that mean you're writing...

while (blah) continue;

...instead of...

while (blah)
{
continue;
}

...these days!

Definitely. Wouldn't have it any other way

int flushln(FILE *f)
{
int ch;

while (('\n' != (ch = getc(f))) && (EOF != ch)) continue;
return ch;
}