strange overload = operator on some book, c-style?

Question

I find some books which this kind of code:

but if I try to compile somethings similar, it says that miss argument?

struct Test {
    double offsetDetected = 0.0;

    Test() {}
    Test &operator=() // removed here
};

what's wrong, and why books write this way those stuff? c-style?

Answer 1

This is C++, there's no "C style" for it. The book you're citing has a typo. That's all. I doubt that you find some "books". You found one book, I bet. The assignment operator requires an argument, since it's a binary operator.

Answer 2

It is a binary operator.As the other asnwere mentioned it might have a typing error.

#include <iostream>

struct Test {
    double offsetDetected = 0.0;

    Test() {}

    Test &operator=(const Test &obj); // removed here
};

int main() {

}