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C++ operator overloading

Started by Asuralm Jan 17, 2008 at 8:47 AM 2 replies 950+ views

Original Post

Jan 17, 2008 at 8:47 AM

Hi all: The code is as follows:

[source lang='cpp']
class My_Class{
public:
....
    inline My_Class operator*(float d){
        ....;
    }
....
}

And when I multiply a float float on the left hand side, like following, it doesn't work.


int main(){
    My_Class x;
    float d;
    My_Class y = d * x;
}

But it works like:


int main(){
    My_Class x;
    float d;
    My_Class y = x * d;
}

Could anyone tell me why this happens please? And how can I overload the operator properly so both left and right handside can work? Thanks

SiCrane

Mod

473

SiCrane

Jan 17, 2008 at 8:56 AM

In order to get a the left hand side of operator* to work with a primitive, you need to declare a non-member operator* overload. Ex:

MyClass operator*(float lhs, const MyClass & rhs) {  do stuff}

Note that this only declares a float * MyClass overload. If you also want a MyClass * float overload you either need to declare the member function overload or another non-member overload with the argument types reversed.

Asuralm

Author

Asuralm

Jan 17, 2008 at 9:06 AM

Thanks.

And I have another question.

If I have a class called my class, how can I overload the unary operator "-" please?
Like:

My_Class x;My_Class y = -x;

Should it be like:

My_Class operator-(){...}

Is it correct?
Thanks

the_edd

115

the_edd

Jan 17, 2008 at 9:37 AM

That's correct, yes. Ideally your operator-() should be const, however:

class My_Class{public:    // ...    My_Class operator-() const { /* ... */ }    // ...};

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