Thread: operator overloading error

Code:

#include <iostream>

using std::cout;
using std::endl;


class CEstimatedInteger
{
private:
	int value;
	bool estimated;

public:
	// Constructor
	CEstimatedInteger(int val = 0, bool est = false) : value(val), estimated(est) { }
	
	// Function to print value and estimation flag
	void Print()
	{
		if (estimated)
			cout << 'E';
		cout << value;
	}

	// Addition operator for operands CEstimatedInteger + int
	CEstimatedInteger operator+(const int& n)
	{
		return CEstimatedInteger(value + n, estimated);
	}

	// Addition operator for operands CEstimatedInteger + CEstimatedInteger
	CEstimatedInteger operator+(const CEstimatedInteger& n)
	{
		return CEstimatedInteger(value + n.value, estimated || n.estimated);
	}
};

CEstimatedInteger operator+(const int& a, const CEstimatedInteger& b)
{
	return b + a;
}

int main()
{
	CEstimatedInteger a;
	return EXIT_SUCCESS;
}

Whats wrong with the above code?

I'm getting the following errors while compiling in Visual Studio 2008

Code:

1>------ Build started: Project: C++Test, Configuration: Debug Win32 ------
1>Compiling...
1>Test.cpp
1>c:\documents and settings\administrator\my documents\visual studio 2005\projects\c++test\c++test\test.cpp(40) : error C2678: binary '+' : no operator found which takes a left-hand operand of type 'const CEstimatedInteger' (or there is no acceptable conversion)
1>        c:\documents and settings\administrator\my documents\visual studio 2005\projects\c++test\c++test\test.cpp(38): could be 'CEstimatedInteger operator +(const int &,const CEstimatedInteger &)'
1>        c:\documents and settings\administrator\my documents\visual studio 2005\projects\c++test\c++test\test.cpp(26): or 'CEstimatedInteger CEstimatedInteger::operator +(const int &)'
1>        c:\documents and settings\administrator\my documents\visual studio 2005\projects\c++test\c++test\test.cpp(32): or 'CEstimatedInteger CEstimatedInteger::operator +(const CEstimatedInteger &)'
1>        while trying to match the argument list '(const CEstimatedInteger, const int)'
1>Build log was saved at "file://c:\Documents and Settings\Administrator\My Documents\Visual Studio 2005\Projects\C++Test\C++Test\Debug\BuildLog.htm"
1>C++Test - 1 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Since your operator + doesn't change the lhs, you should specify as much:

Code:

CEstimatedInteger operator+(const int& n) const

Didn't know it's mandatory

tY

Originally Posted by manzoor

Didn't know it's mandatory

tY

It's only mandatory if you want to use it on a const variable (which you do in your other operator +). It's a good idea, always.