구조체를 사용한 복소수의 절대값만들기.

#include
#include

struct number{
double realnumber;
double imaginarynumber;
};
typedef struct number number;

void add(number number1, number number2){
printf("덧셈 \n");
double x, y, a, b;
x = number1.realnumber;
y = number1.imaginarynumber;
a = number2.realnumber;
b = number2.imaginarynumber;
printf("(%.2lf+%.2lfi) + (%.2lf%.2lfi) = (%.2lf + %.2lfi)\n", x, y, a, b, x + a, y + b);
printf("\n");
}
void minus(number number1, number number2){
printf("뺄셈 \n");
double x, y, a, b;
x = number1.realnumber;
y = number1.imaginarynumber;
a = number2.realnumber;
b = number2.imaginarynumber;
printf("(%.2lf+%.2lfi) - (%.2lf%.2lfi) = (%.2lf + %.2lfi)\n", x, y, a, b, x - a, y - b);
printf("\n");
}
void multiply(number number1, number number2){
printf("곱셈 \n");
double x, y, a, b;
x = number1.realnumber;
y = number1.imaginarynumber;
a = number2.realnumber;
b = number2.imaginarynumber;
printf("(%.2lf+%.2lfi) * (%.2lf%.2lfi) = (%.2lf %.2lfi)\n", x, y, a, b, (x * a) + (-(y*b)), (x * b) + (y*a));
printf("\n");
}

void abs(number number2){
double x, y;
x = number2.realnumber;
y = number2.imaginarynumber;
printf("%.2lf", sqrt(x*x + y*y));
}

void main(){
number number1 = { +4.50, +5.60 };
number number2 = { -3.70, -5.50 };
add(number1, number2);
minus(number1, number2);
multiply(number1, number2);
printf("첫번째 복소수 절대값 \n");
abs(number1);
printf("두번째 복소수 절대값 \n");
abs(number2);
}

문제인 부분은 abs함수인데요 오류 나오는것이 cannot convert from 'number' to 'int'라고 뜨는데.. abs 부분에 int로 바꾸는부분도 없는데 왜이러는거죠??