overload operator+ in format (z + obj2)

I need help to overload the operator + in the format (z + obj2).

I have done it in two formats where 'n' becomes the sum of two objects and 'z' is z (scalar variable/constant/expression).
1. n = obj2 + obj 1 (done)
---> declaration
double operator+(const product&);
----> definition
// Overloading the operator+ (productObj2 + productObj1)
double product:perator +(const product & rhs)
{
return (*this).productCost + rhs.productCost ;
}

2. n = obj2 + z (scalar variable/constant/expression) (done)
---> declaration
double operator+(const double&)----> definition
----> definition
double product:perator +(const double & rhs)
{
cout << "The operator+ (productObj2 + z) function ran." << endl;
return (*this).productCost + rhs ;
}


3. n = z + obj2 <---------- Need help/tips/comments to overload operator +

<Need help/tips/comments to overload operator + in the above format>

Thanks.

Make it a friend to the class, with the signature operator+(const double &, const obj &)

Thanks zx-1, for you reply. But I am still having the issue.

Declaration-->
friend double operator+(const double&, const product &);

Definition-->
double product:: operator +(const double & num, const product & rhs )
{
......
}

But I am still getting the following error:
error C2511: '+' : overloaded member function 'double (const double &,const class product &)' not found in 'product'


I am not sure why compiler is still complaining?

Originally Posted by zx-1

Make it a friend to the class, with the signature operator+(const double &, const obj &)

Because the friend is not a member. Remove the product:: from the definition.

It worked finally!! Thanks a lot for the quick reply.

Originally Posted by CornedBee

Because the friend is not a member. Remove the product:: from the definition.

I am trying to overload operator+=, so that "obj += n" functionality can be accomplished. The code below doesn't put the new value added value of "obj + n" in obj data member.

Can somebody please point the error in the following syntax and help me get the correct syntax to accomplish "obj+= n" functionality?

Code:

double productCost ; // a private member of the class

Declaration:
double operator+=(const double);

Definition:
double product::operator +=(const double pCost)
{
    (*this).productCost = (*this).productCost + pCost ;
    return (*this).productCost;
}

Thanks in advance.

your code actually looks like it should work.
typically with ops like +=, -= and so on, you generally return a reference to this to allow operator chaining

Code:

Declaration:
class product
{
public:
    // constructors, etc
    product &operator+=(double cost); // const not necessary

private:
    double productCost; 
};

Definition:
product & product::operator +=(double cost)
{
    this->productCost += cost;
    return *this;
}

The declaration (if you're making it a member function) should read:

Code:

double product::operator+=(double);

Other than that, it should work fine. You don't have to use (*this).productCost to reference that member. You can access the private members by name, like this:

Code:

double product::operator+=(double pCost)
{
  productCost += pCost;
  return pCost;
}

[edit]oops, beaten...I went off to test something and forgot to check if anyone had replied...

Originally Posted by slrj

I am trying to overload operator+=, so that "obj += n" functionality can be accomplished. The code below doesn't put the new value added value of "obj + n" in obj data member.

Can somebody please point the error in the following syntax and help me get the correct syntax to accomplish "obj+= n" functionality?

Code:

double productCost ; // a private member of the class

Declaration:
double operator+=(const double);

Definition:
double product::operator +=(const double pCost)
{
    (*this).productCost = (*this).productCost + pCost ;
    return (*this).productCost;
}

Thanks in advance.

Why are you writing so much more than you need to?
(*this). is redundant.
And why not use operator += internaly?

Code:

double product::operator +=(double pCost)
{
    productCost += pCost;
    return productCost;
}

Also, you would usually return a reference to the object being modified:

Code:

return *this;

ChaosEngine/Decrypt/Imalc,

I really appreciate your help and tips. My code works now.

Thanks.

The overloading of extraction operator(>>) is giving the following errors. The insertion (<<)operator is working within the code. It looks like there are some header files missing to be included? or there are other errors which I can't see.

Code:

Declaration:
 #include <iostream>
.
.
class x{
	friend ostream &operator<<(ostream &, const product &); <--- Work fine
	friend istream &operator>>(istream &, product &); <---- Giving the errors shown below 

public:
}


Definition:
istream &operator >>(ostream &input, product &p)
{
.........
}

Compiler Error: 
------------------Configuration: useProduct - Win32 Debug--------------------
Compiling...
product.cpp
error C2143: syntax error : missing ';' before '&'
error C2433: 'istream' : 'friend' not permitted on data declarations
error C2501: 'istream' : missing storage-class or type specifiers
error C2244: 'istream' : unable to resolve function overload
error C2061: syntax error : identifier 'istream'
 error C2501: '>>' : missing storage-class or type specifiers
error C2805: binary 'operator >>' has too few parameters
Error executing cl.exe.

product.obj - 7 error(s), 0 warning(s)

Thanks.

Either add

Code:

using namespace std;

immediately after your #include line, or prefix istream/ostream etc with std::

Skeane,

I do have "using namespace std:" declared in the .cpp class definition, but the problem still persists. Do you have any other suggestions?

Originally Posted by SKeane

Either add

Code:

using namespace std;

immediately after your #include line, or prefix istream/ostream etc with std::

Typo caught in definition of the overloaded function (&operator>>). The parameter "input" should have been of type "istream" instead of "ostream".

Incorrect Definition:
istream &operator >>(ostream &input, product &p)
{
.........
}

Correct Definition:
istream &operator >>(istream &input, product &p)
{
.........
}


Thanks.

Originally Posted by slrj

The overloading of extraction operator(>>) is giving the following errors. The insertion (<<)operator is working within the code. It looks like there are some header files missing to be included? or there are other errors which I can't see.

Code:

Declaration:
 #include <iostream>
.
.
class x{
	friend ostream &operator<<(ostream &, const product &); <--- Work fine
	friend istream &operator>>(istream &, product &); <---- Giving the errors shown below 

public:
}


Definition:
istream &operator >>(ostream &input, product &p)
{
.........
}

Compiler Error: 
------------------Configuration: useProduct - Win32 Debug--------------------
Compiling...
product.cpp
error C2143: syntax error : missing ';' before '&'
error C2433: 'istream' : 'friend' not permitted on data declarations
error C2501: 'istream' : missing storage-class or type specifiers
error C2244: 'istream' : unable to resolve function overload
error C2061: syntax error : identifier 'istream'
 error C2501: '>>' : missing storage-class or type specifiers
error C2805: binary 'operator >>' has too few parameters
Error executing cl.exe.

product.obj - 7 error(s), 0 warning(s)

Thanks.

Code comiples on Unix (Solaris) but not on Visual C++? Any suggestions....

--------------------Configuration: useProduct - Win32 Debug--------------------
Compiling...
product.cpp
c:\scc\assign 2\product.h(39) : fatal error C1001: INTERNAL COMPILER ERROR
(compiler file 'msc1.cpp', line 1786)
Please choose the Technical Support command on the Visual C++
Help menu, or open the Technical Support help file for more information
Error executing cl.exe.

product.obj - 1 error(s), 0 warning(s)