float square(float x) {
    return x * x;
}
float area = square(2);

square(float x) {
    return x * x;
}
float area = square(2);

void square(float x) {
    return x * x;
}
area = square(2.0);

void square(float x) {
    x * x;
    return;
}
area = square(2);