Overloading ** in C++

Question

In Python, we have nice simple syntax to take an arbitrary int/float to a power. Namely, for you non-Python programmers, we can have the following statement:

y = 2 ** 3 
print y

This will print 8 to the console, and has nice syntax as there is a built in "power" operator. Is it possible to overload "**" as a single operator in C++? Specifically, I want to accomplish something like this:

int a = 2;
int b = 3;
cout << (a**b) << endl;

or, if this isn't possible, something like this:

MyInt a = new MyInt(2); // Wrapper class around ints to play nicely with **
MyInt b = new MyInt(3);
cout << (a**b) << end; // Assume ostream overridden for MyInt

These should also print 8 to console. I understand that it would be much easier to override the "^" operator to do the same thing, but I'm mostly interested to see whether or not I can overload "**". Would the operator "*" (for the MyInt class case, if it were a member function) have to look to see if the argument was another "*", as I don't know of a way to specify "**" as a single operator? Is it even possible to pass an operator as an argument?

Additional/bonus stipulation if possible (as if I haven't already said enough): No macros!!!

Answer 1

You mean something like this?

#include <iostream>
#include <cmath>

struct MyInt {
    int val;
    struct MyProxy { int val; };

    MyProxy operator *() const{ return MyProxy{val}; }
    MyInt operator * (const MyProxy& b) { return MyInt{ static_cast<int>(std::pow(val, b.val)) }; }

};

std::ostream& operator << (std::ostream& o, const MyInt& m) { return o << m.val; }

int main(){
    MyInt a{5}, b{3};
    std::cout << a**b << std::endl;
}

See it live here http://coliru.stacked-crooked.com/a/ab56b9cd6e422e12

Explanation:

1. Overload the unary * operator to return a proxy object
2. Overload the binary * operator to use the proxy... Simple :-)
3. I used a proxy class to avoid subtle bugs..

C++ is fun... I want to believe you are doing this for fun AND not in production... Cause its a very bad idea in production, just call std::pow

Answer 2

Short answer: No. There is no way to "overload" arbitrary character/token sequences in C++.

Longer answer: a**b is equivalent to a * (*b), so you could overload both binary * (i.e. multiply) and unary * (i.e. dereference) in some gross way. But that would be completely opaque/unexpected to anyone reading your code, and painful to debug/maintain in future.

Just write a function called pow()!