another printf question!!

[drM]

I have looked at the faq and queried the archives, but cannot seem to
be able to get this to work. It's the usual factorial recursive
function, but that is not the problem. It hangs after the user enters a
number. However, as I indicate, if one adds something else after the
number, the function proceeds and finishes successfully.

I would appreciate some helpful hints.
thanks in advance.

>>>>>
#include <stdio.h>
#include <math.h>

int factorial( int);
main() {

int i, k;

printf ( "Please enter a number "); // <<<<< seems to hang here if
user enters number only, but
// works if user enters number eg 8 plus something else eg the letter
"m".
scanf (" %d ", &i);

k = factorial (i);
printf ( " the factorial of %d is %d\n ", i, k);

return (0);

}
int factorial ( int j){
if (j == 1)

return 1;

return j * factorial(j-1);

}
>>>>>

[David Barkol]

Remove the spaces from your scanf call:
scanf("%d", &i);

David Barkol
www.neudesic.com

[drM]

David,
You are a genius!!! But why...I thougth in C spaces did not count?

[David Barkol]

scanf reads formatted data from the standard input stream. This means
that if you have a format like: "%d %d" then scanf will not return
until you enter in two numbers seperated by a space. For example: 24
14. When dealing with formatting, spaces always count.

[drM]

thank you,

[Alan Balmer]

On 2 Feb 2005 14:24:08 -0800, "drM" <md**@comcast.n et> wrote:

David,
You are a genius!!! But why...I thougth in C spaces did not count?

Spaces in quotations are significant. In your scanf call, you could
write
scanf ( "%d " , &i );

without making a difference (except to the unfortunate person reading
it),.

--
Al Balmer
Balmer Consulting
re************* ***********@att .net

[drM]

It makes sense now...all part of the learning curve. Thanks for your
input.

[Default User]

drM wrote:

thank you,

Please learn to use the correct reply method when using the Google
interface. Click "show options" to expand the header of the message you
are replying to, then the Reply shown there. Don't use the one at the
bottom of the message. You'll then have proper attributions and quotes,
so people can understand what you are refering to.


Brian

[Mark McIntyre]

On 2 Feb 2005 14:45:11 -0800, in comp.lang.c , "drM" <md**@comcast.n et>
wrote:

It makes sense now...all part of the learning curve. Thanks for your
input.

You may also want to consider not using scanf for user input - its not very
robust or secure. Its often better to use fgets and sscanf. As you've
found scanf can't handle unexpected input very well.

What does this programme do, if the user types in "one" as the response?

#include <stdio.h>

int main(void)
{
int x=1;

printf("think of a number\n");
while(x > 0)
scanf("%d", &x);

return 0;
}

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

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[Taran]

drM wrote:

I have looked at the faq and queried the archives, but cannot seem to
be able to get this to work. It's the usual factorial recursive
function, but that is not the problem. It hangs after the user enters a number. However, as I indicate, if one adds something else after the
number, the function proceeds and finishes successfully.

I would appreciate some helpful hints.
thanks in advance.

>>>>>>
#include <stdio.h>
#include <math.h>

int factorial( int);
main() {

int i, k;

printf ( "Please enter a number "); // <<<<< seems to hang here if
user enters number only, but
// works if user enters number eg 8 plus something else eg the letter
"m".
scanf (" %d ", &i);

k = factorial (i);
printf ( " the factorial of %d is %d\n ", i, k);

return (0);

}
int factorial ( int j){
if (j == 1)

return 1;

return j * factorial(j-1);

}
>>>>>>>

I faced the same problems when I was new to C. Learned the hard way
though. Have been paranoid about scanf ever since. :)
A book on C by Schaum's Series was helpful regarding the nuances on
scanf. Sorry don't excatly remember the name. I rather you go thru it
once.

HTH

Regards,
Taran