Explicitly allow for typecasting between primary and user defined type

Question

I have a Fraction class that I want to be able to typecast to a double. Is there a way to write that explicitly? (Like operator overloading)

This is my constructor:

Fraction::Fraction(double n, double d) : numerator(n), denominator(d)
{
    if (d == 0) throw Error::DIVIDE_BY_ZERO;
}

When overloading operators, e.g.:

bool operator==(const Fraction& left, const Fraction& right)

I want that overload to be able to take a double as well without having to write overloads with (const Fraction&, const double) and (const double, const Fraction&)

it's not clear for me, do you want your overloading implementation of operator == to accept both `Fraction` and `double` as input? — bogdan tudose, Feb 09 '19 at 13:43
@bogdantudose Yes, that was my goal. The reference solved my problem. — snzm, Feb 09 '19 at 13:46

score 0 · Answer 1 · answered Feb 09 '19 at 14:15

I would use template specialization for this task instead of cast_operator.

template<typename T>
friend bool operator==(const T& left, const T& right) // member template

Also you should implement your operator overloading as free function (with friend) otherwise you cannot pass two arguments to it.

Please refer to operator == overloading

Explicitly allow for typecasting between primary and user defined type

1 Answers1