How do they represent complex numbers in C?

Question

How to represent a complex number z = x + yi?

Answer 1

It would be by including complex.h:

#include <stdio.h>
#include <complex.h>

int main() {
    double x = 1.0;
    double y = 2.0;
    double complex z = x + y * I;
    printf("%.2f %+.2fi\n", creal(z), cimag(z));
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.