#include <stdio.h>

struct cmplx {
	double a;
	double b;
};

struct cmplx cprod(struct cmplx za, struct cmplx zb) {
	struct cmplx tmp;
	tmp.a = za.a*zb.a-za.b*zb.b;
	tmp.b = za.a*zb.b+za.b*zb.a;
	return tmp;
}

int main(int argc, char const* argv[])
{
	struct cmplx a = {1,2};
	struct cmplx b = {2,4};
	struct cmplx c = cprod(a,b);
	printf("%f+%fi * %f+%fi = %f+%fi\n",
			a.a,a.b,
			b.a,b.b,
			c.a,c.b);
	return 0;
}