Question

Operator ovleroading errors

Asked by: Falmarri

So I'm learning about operator overloading in class, and I totally get the concept, but I'm having syntax issues and such. Here are the methods that aren't compiling. First, I was under the impression you should have 2 different operator[] overloads for assignment and read only. It's says however

/home/falmarri/Dropbox/Programs/hw06-knapp-david/src/polyclass.h:34: error: int& PolyClass::operator[](int) cannot be overloaded

/home/falmarri/Dropbox/Programs/hw06-knapp-david/src/polyclass.h:32: error: with const int PolyClass::operator[](int)

And then I get several of these:

/home/falmarri/Dropbox/Programs/hw06-knapp-david/src/polyclass.cpp:147: error: std::ostream& PolyClass::operator<<(std::ostream&, const PolyClass&) must take exactly one argument

I was told that errors like that suggest that I've forgotten to make that method a friend function. But I've included it as a friend like I know how. It may not be correct.

/home/falmarri/Dropbox/Programs/hw06-knapp-david/src/polyclass.cpp:100: error: PolyClass PolyClass::operator+(const PolyClass&, const PolyClass&) must take either zero or one argument

I can post more information if needed, I'd prefer not to post all my source though. I'm assuming it's just fundamental misunderstanding of how this works.

32	const int operator[] ( const int lhs);
	
34	int& operator[] (const int lhs);
 
 
	friend std::ostream &operator<<(std::ostream &out, const PolyClass& rhs);

                                  
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Asked On
2009-10-29 at 23:45:32ID24857245
Tags

C++

,

operator

,

overloading

,

operator overloading

Topics

Microsoft Visual C++.Net

,

C++ Programming Language

Participating Experts
2
Points
500
Comments
8

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Answers

 

by: Let_Me_BePosted on 2009-10-30 at 00:03:25ID: 25700596

It is what it says int& operator[] (const int lhs); and const int operator[] ( const int lhs); cannot be in a class together. You probably meant int operator[] ( const int lhs) const; instead of const int operator[] ( const int lhs);

 

by: Let_Me_BePosted on 2009-10-30 at 00:06:31ID: 25700606

The one argument errors mean, that you implemented something as a method but forgot to adjust the number of parameters accordingly.

PolyClass::operator+ is a clear indication its not a friend but a method.

 

by: Subrat2009Posted on 2009-10-30 at 01:02:06ID: 25700839

Operator overloading never depends upon return type.

 

by: Let_Me_BePosted on 2009-10-30 at 01:06:54ID: 25700858

> Operator overloading never depends upon return type.

Any type of overloading. Return type is not part of the prototype (function, method, operator).

 

by: Subrat2009Posted on 2009-10-30 at 01:19:57ID: 25700902

>>Return type is not part of the prototype
Hi Let_Me_Be can u plz tell me more about this

Lets I'm going to write prototype of a function which accepts two ints and returns int
I should write int Fun(int, int) as the prototype.
Shall I write Fun(int, int)   as the prototype?
My Ans:   No.
Possible in C but not at _all_ in C++ which is strictly prohibited.

So how can I omit the return type????? How can I say it's not part of the prototype?
Plz let me know if I'm missing something...

 

by: Let_Me_BePosted on 2009-10-30 at 01:27:23ID: 25700934

Well, that depends on what you consider a prototype. int Fun(int,int); is a function declaration, or a function header. The prototype is actually "two params, first type int, second type int".

Also the return type is not included in the mangled symbol name.

 

by: FalmarriPosted on 2009-10-30 at 01:40:54ID: 25701003

That totally makes sense Let_Me_Be. I never thought about why it was MyClass::Method() before.

 

by: Subrat2009Posted on 2009-10-30 at 02:08:44ID: 25701154

Hi
Plz have a look on http://en.wikipedia.org/wiki/Function_prototype

A function prototype in C or C++ is a declaration of a function that omits the function body but does specify the function's name, arity, argument types and return type.

Thanks,
Subrat

20120131-EE-VQP-002

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