#include <stdio.h>
#include <stdlib.h>

/* 複素数型の定義 */
typedef struct { double re, im; } Complex;

/* 複素数の初期化関数 */
Complex ComplexInit(double re, double im)
{
	Complex c;

	c.re = re;
	c.im = im;

	return (c);
}

/* 複素数を表示する関数 */
void ComplexPrint(char *str, Complex c)
{
	if (c.im < 0.0) {
		printf("%s %f - %f i\n", str, c.re, -c.im);
	} else {
		printf("%s %f + %f i\n", str, c.re, c.im);
	}
}

/* 複素数の積を計算する関数 */
Complex ComplexProduct(Complex a, Complex b)
{
	Complex c;

	c.re = a.re*b.re - a.im*b.im;
	c.im = a.re*b.im + a.im*b.re;
	return (c);
}

/* メイン関数 */
int main()
{
	Complex a = {1.0, 1.0};
	Complex b, c;

	b = ComplexInit(1.0, -1.0);
	ComplexPrint("a = ", a);
	ComplexPrint("b = ", b);

	c = ComplexProduct(a, b);
	ComplexPrint("a*b = ", c);

	return (EXIT_SUCCESS);
}