operator overloading error

This is a discussion on operator overloading error within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream> using std::cout; using std::endl; class CEstimatedInteger { private: int value; bool estimated; public: // Constructor CEstimatedInteger(int val ...

  1. #1
    Registered User
    Join Date
    Nov 2007
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    164

    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 ==========

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Since your operator + doesn't change the lhs, you should specify as much:
    Code:
    CEstimatedInteger operator+(const int& n) const

  3. #3
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    Didn't know it's mandatory

    tY

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by manzoor View Post
    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.

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