Problem with overloading an operator.

**apacz** · 08-04-2006

Hello,
I have to overload "<" and ">" operators. So I do:

Code:

bool bignum::operator<(const bignum& a)
{
        // here is some code comparing *this and a.
}

now I want to use operator "<" to overload ">":

Code:

bool bignum::operator>(const bignum& a)
{
        return  a < *this;
}

and I get a compile error:

main.cpp: In member function `bool bignum::operator>(const bignum&)':
main.cpp:157: error: passing `const bignum' as `this' argument of `bool bignum::operator<(const bignum&)' discards qualifiers

Can anyone help me ?
--
Regards,
apacz

**laserlight** · 08-04-2006

I suggest making them friend functions, and then writing:

Code:

bool operator<(const bignum& lhs, const bignum& rhs)
{
	// here is some code comparing lhs and rhs.
}

bool operator>(const bignum& lhs, const bignum& rhs)
{
	return rhs < lhs;

Making them friend functions means that expressions like (1 < x) will be allowed, assuming that int is convertible to bignum (e.g. via a non-explicit constructor that accepts an int).

**apacz** · 08-04-2006

Thanks. But there is no way to make this overload look like: bool operator<(const bignum& rhs) ? Because your overload takes two arguments - what's the real difference between those two versions ?
--
Regards,
apacz

**laserlight** · 08-04-2006

But there is no way to make this overload look like: bool operator<(const bignum& rhs) ?

Yes, there is. Make your member function versions const.

Because your overload takes two arguments - what's the real difference between those two versions ?

The useful difference is what I mentioned: the friend function version is more flexible than the member function version. Actually, since operator> is implemented in terms of operator< you do not even need to make it a friend function.

Thread: Problem with overloading an operator.

Thread Tools

Search Thread

Display

Problem with overloading an operator.

Similar Threads

operator overloading slight problem

oops? not sure. operator overloading (possible) problem

bug in my operator += overloading method?

Full operator overloading in BCB5

operator overloading