C++ Overload operator% for two doubles

is it possible to overload the operator% for two doubles?

const double operator%(const double& lhs, const double& rhs)
{
    return fmod(lhs, rhs);
}

Of course, this generates an error because one of the two parameters must have a class type. So I thought about utilizing the possibility of implicit constructor calls of C++ to get around of this problem. I did it in the following way:

class MyDouble {
public:
    MyDouble(double val) : val_(val) {}
    ~MyDouble() {}

    double val() const { return val_; }

private:
    double val_;
};


const double operator%(const MyDouble& lhs, const double& rhs)
{
    return fmod(lhs.val(), rhs);
}

const double o开发者_运维百科perator%(const double& lhs, const MyDouble& rhs)
{
    return fmod(lhs, rhs.val());
}

... and:

double a = 15.3;
double b = 6.7;

double res = a % b; // hopefully calling operator%(const MyDouble&, const double) using a implicit constructor call

Unfortunately, this does not work! Any hints, ideas, ... are appreciated! Thanks in advance, Jonas

---

The reason this doesn't work is because overload resolution for user defined operator functions is only triggered if at least one operand of the expression has a class or enumeration type.

So you are out of luck. This won't work.

I think the best you could try is waiting for a C++0x compiler and instead of writing 3.14, you write 3.14_myd, as a user defined literal.

---

alternatively, implement double MyDouble::operator%(const double&) const;, like so:

#include <iostream>
#include <cmath>

class t_double {
public:
    t_double(const double& val) : d_val(val) {
    }

    t_double(const t_double& other) : d_val(other.d_val) {
    }

    ~t_double() {
    }

    const double& val() const {
        return this->d_val;
    }

    double operator%(const double& rhs) const {
        return fmod(this->val(), rhs);
    }

    double operator%(const t_double& rhs) const {
        return fmod(this->val(), rhs.val());
    }

private:
    double d_val;
};

int main(int argc, char* const argv[]) {

    const t_double a(15.3);
    const t_double b(6.7);

    std::cout << a % b << " == " << a.val() << " % " << b.val() << "\n";

    return 0;
}