I need to get the factorial of the number n inputted by the user and I have to use the for loop without a body to get the factorial. But in that case the scope of the variable k is the for loop, and when I try to print the k after the loop, it prints 1 (i. e. the value as k was initialized). What can I do?
Code:#include <stdio.h> int main(void) { int n, k = 1; scanf("%d", &n); for (int i = 1, k; i <= n; k *= i, i++); printf("%d", k); return 0; }
Remove the declaration of k from the loop.
Anyway, this is a bad idea: the updating of k logically belongs in the loop body, so taking it out just to have more concise code is pointless. Sometimes, you will find that there really is no reason to have anything in the loop body, in which case go ahead and make it empty.
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
Just remove the k
E.g.
That will work, but even better would be to avoid using the comma operator for no (good) reasonCode:for (int i = 1; i <= n; k *= i, i++) ;
Edit: Notice in the first example I gave I moved the semicolon to a line of its own and indented it? This is not for the compiler (which doesn't care). This is for readability for both you and other human beings. It makes it clear that "yes, I meant this loop to have an empty body" and didn't accidentally put the semicolon there. Some compilers (clang at least, I haven't even checked gcc but I suspect it now behaves the same) will warn if the semi-colon isn't on the next line and at a larger indentation level than the actual for(...)Code:for (int i = 1; i <= n; i++) k *= i;
Last edited by Hodor; 11-28-2015 at 01:29 AM.
Thanks Hodor and laserlight, removed the k and it worked fine! And I know that I could write the k *= i; part inside the body of for but I needed to achieve the result with an empty-body-for.
Well, you could still do it without using the comma operator. E.g.
Although I will concede that this is just as obfuscated (perhaps more so, depending on your point of view) and pointless as using the comma operator. But if it's for a class exercise or something then I guess ya just have to go with the flow.Code:for (int i = n + 1; --i > 1; k *= i) ;
