在C中加倍到int

Question

I have this code :

#include <stdio.h>

int main ()
{
    double d = 10;
    int x = 5;

    x = (int) d + x;
    d = (double)x + d;

    printf("%lf\n" , d);
    printf("%d\n" , x);
}

the out put is :

-0.0000
15

Why is this working for int but not for double ? How to make this work?

Answer 1

In C89 use %f format specifer to print double value. With newer standards you might use %lf , in which case l has no effect (it was introduced for symmetry with scanf() ), but it's just asking for trouble, as it's undefined in previous standard.

#include <stdio.h>

int main(void)
{
    double d = 10;
    int x = 5;

    x = (int) d + x;
    d = (double)x + d;

    printf("%f\n", d);
    printf("%d\n", x);

    return 0;
}

Note that in C89 you probably should add return 0; . With C99/C11 return 0; is implicitly added when omitted (with exception to call of exit() function directly in main() , which serves for that as well).

Answer 2

Works fine for me

http://ideone.com/YBfHau

    #include <stdio.h>

int main ()
{
    double d = 10;
    int x = 5;

    x = (int) d + x;
    d = (double)x + d;

    printf("%lf\n" , d);
    printf("%d" , x);
return 0;

}

EDIT: Remember to add return 0