错误 C2677：二进制“*”：未找到全局运算符

Question

Sorry for asking a similar question that has been asked before, but I wasn't able to understand the answers.

Header file

    float Dot(const Point& other) const;

CPP

Point Point::operator*(float operand) const
{
    return Point(mX * operand, mY * operand);
}

and I am getting Error C2677: binary '*': no global operator found

what is the problem??

Answer 1

You have implemented operator* in the cpp file but in the header file you only declared a simple Dot function.

You either move the operator* inline in the header file or you add a declaration for it in the header file, ie:

Class Point {
[...]
    Point operator*( float operand ) const {
        return Point( mX * operand, mY * operand) );
    } 
};

That operator defined that way is a member operator because you have declared inside the class itself. You might also want to add a global operator , for example a comparison operator, which you will place outside your class declaration, for example:

Class Point {
[...]
    Point operator*( float operand ) const {
        return Point( mX * operand, mY * operand) );
    } 
};

bool operator==(const Point& left, const Point& right) 
{
    return left.value == right.value;
};

Final thought:

So to recap the error you've got it most probably means that you didnt' declare the operator* as global operator as shown above. Also I think you might confusing a dot product with a multiplication, (operator*), which held two very different results, also notice one is a scalar operation (in any dimension), the other is a Point, in this case, two dimension.