#include <complex>
#include <cstdio>
#include <random>

int
main()
{
    std::random_device                      random;
    std::uniform_real_distribution<double>  uniform(-100, 100);

    std::complex<double> z(uniform(random), uniform(random));

    printf("z = (%lf, %lf)\n", z.real(), z.imag());

    // or

    z = std::complex<double>(uniform(random), uniform(random));

    printf("z = (%lf, %lf)\n", z.real(), z.imag());
}