Thread: How efficient do you think is this Int To String Converter Function?

Originally Posted by babaliaris

Nice tip!!

Yeah. Except it doesn't actually do what it's supposed to do :/

Edit: viz, eliminate undefined behaviour is what the tip is, I assume, intended to do but it doesn't

Because the negative side of the integer has more numbers than the positive one, about the only thing you can do to switch the sign safely is use a bigger type.
One notices that there are no problems with this example...

Code:

#include <stdio.h>
#include <stdint.h>
#include <limits.h>
int main(void) {
   printf("%lu\n", -(uint64_t)INT_MIN);
   return 0;
}

Originally Posted by Hodor

Yeah. Except it doesn't actually do what it's supposed to do :/
Edit: viz, eliminate undefined behaviour is what the tip is, I assume, intended to do but it doesn't

Hodor is right, but only because I (obviously) made a mistake, due to haste. It should be:

Code:

void print_int(int n) {
    unsigned u;
    if (n < 0) {
        u = (unsigned)(-(n + 1)) + 1u;
        putchar('-');
    } else
        u = n;
    print_uint(u);
}

Originally Posted by whiteflags

Because the negative side of the integer has more numbers than the positive one, about the only thing you can do to switch the sign safely is use a bigger type. One notices that there are no problems with this example...

There's nothing wrong with the corrected version of my example.
And since you will eventually run out of bigger types, the unsigned trick is generally better.