defining a template class problem

[dvirol]

Hi,

I have defined the following class:

template<class T,char var>
class CGenPoly : public CList
{
    
public:
	CGenPoly();
	//genpoly(int num);
	CGenPoly(T elem);
	CGenPoly(const CGenPoly& p);
	void SetCoef(int power,T elem);   //Omri
	CGenPoly operator+ (const CGenPoly& p); 
	CGenPoly operator* (const CGenPoly& p);
	CGenPoly& operator+= (const CGenPoly& p);
	CGenPoly& operator*= (const CGenPoly& p);    
	CGenPoly& operator= (const CGenPoly& p);   //Omri
	CGenPoly operator^ (int power);  // Omri
    CGenPoly operator* (const T& elem);
    CGenPoly operator+ (const T& elem);  //Omri  //poly + T
	T operator() (T point);    
	friend ostream& operator << <T,var>(ostream& os, const CGenPoly& p);  //Omri
	friend CGenPoly operator * <T,var>(const T& elem, const CGenPoly& p);
       friend CGenPoly operator + <T,var>(const T& elem, const CGenPoly& p);  // Omri  //T + poly

};

all the methods are ok except of the last two. I get the following error about those two:
genpoly.h(85) : error C2143: syntax error : missing ';' before '<'

I can't find what I did wrong and I would appreaicate it if someone could help me.

Thanks

[Codeplug]

This should clear up your syntax issues: http://www.parashift.com/c++-faq-lit...html#faq-35.16

Here's how to use code tags for the next time you post code
http://www.codeguru.com/forum/misc.php?do=bbcode#code

gg

[Paul McKenzie]

CGenPoly operator^ (int power);  // Omri

This is not going to work as you expect. Operator ^ has low precedence, not high precedence as a true "power" operator would need.

That's why you won't find any C++ based math libraries overloading operator ^ to do powers -- it just won't work correctly.

Regards,

Paul McKenzie

[dvirol]

I am sorry for not posting my massage right.

It was the first time for me.

Thanks a lot for your answers.

[dvirol]

Paul,

how low is the precedence of the Operator ^?

is it even lower than +?

what if I try it like that: "(x+1)^3"

will it work?

[dvirol]

This should clear up your syntax issues: http://www.parashift.com/c++-faq-lit...html#faq-35.16

Here's how to use code tags for the next time you post code
http://www.codeguru.com/forum/misc.php?do=bbcode#code

gg

I tried using what was said there and it still won't work.

I suspect the problem in my program is in this line

friend CGenPoly<T,var> operator* <T,var>(const T& elem, const CGenPoly& p);

I also tried like that:

friend CGenPoly<T,var> operator* <T,var>(const <T>& elem, const CGenPoly& p);

and it didn't work. I think I am using "T" wrong.
(this line is found in the class declaration.)

The following declaration for operator << is working:

friend ostream& operator << <T,var>(ostream& os, const CGenPoly& p);

Can you see how I can fix it?

[GrimmRiffer]

Why is there a template parameter list in each of your friend function declarations?

friend CGenPoly operator * <T,var>(const T& elem, const CGenPoly& p);

[Peter_B]

Why is there a template parameter list in each of your friend function declarations?

friend CGenPoly operator * <T,var>(const T& elem, const CGenPoly& p);

And this one doesn't even use them:

	friend ostream& operator << <T,var>(ostream& os, const CGenPoly& p); //Omri

[dvirol]

I got it working like this if you are interested:

public:
	CGenPoly();
	CGenPoly(T elem);
	CGenPoly(const CGenPoly& p);
	void SetCoef(int power,T elem);   //Omri
	CGenPoly operator+ (const CGenPoly& p); 
	CGenPoly operator* (const CGenPoly& p);
	CGenPoly& operator+= (const CGenPoly& p);
	CGenPoly& operator*= (const CGenPoly& p);    
	CGenPoly& operator= (const CGenPoly& p);   //Omri
	CGenPoly operator^ (int power);  // Omri
        CGenPoly operator* (const T& elem);
        CGenPoly operator+ (const T& elem);  //Omri
        T operator() (T point);    
        friend ostream& operator << <T,var>(ostream& os, const CGenPoly& p);  //Omr

};
  template<class T,char var>
  CGenPoly<T,var> operator* (const T& elem,  CGenPoly<T,var>& p);
  template<class T,char var>
  CGenPoly<T,var> operator+ (const T& elem, CGenPoly<T,var>& p);  // Omri

However, the code works only in VS.
When I try to compile it with GNU g++ it still makes some problems.
Please let me know if you can see why that happens, while I keep searching for it myself.

[Codeplug]

>> Can you see how I can fix it?
Go back and re-read the article. It shows all the various ways it can be fixed. You're trying to mix syntax rules for the various ways it could be fixed.

Also, always assume that errors/warnings provided by the compiler are relevant when posting code that doesn't compile.

#include<iostream>
using namespace std;

// forward declarations of CGenPoly
template<class T, char v> 
class CGenPoly;

// forward declaration to explicitly declare foo() as a template function
template<class T, char v> 
CGenPoly<T,v> foo(const CGenPoly<T,v> &p);

template<class T, char v>
class CGenPoly 
{
public:
    // template syntax not used, must be implemented inline
    friend ostream& operator << (ostream &os, const CGenPoly &p)
    {
        return os;
    }//operator ostream << CGenPoly

    // template parameters explicitly written on CGenPoly, must be inline
    friend CGenPoly<T,v> operator * (const T &elem, const CGenPoly<T,v> &p)
    {
        return CGenPoly<T,v>();
    }//operator*

    // template syntax used explicitly, (declaring new template parameter names
    // when implemented inline), function body may be moved outside the class
    // without a forward declaration since it's declared as a template function
    // here.
    template<class U, char v1>
    friend CGenPoly<U,v1> operator + (const U &elem, const CGenPoly<U,v1> &p)
    {
        return CGenPoly<U,v1>();
    }//operator+

    // "template" syntax not used, foo must be forward declared as a template 
    // and "<>" syntax used here so compiler knows we are referring to the 
    // template function foo (and not some other foo)
    // note: "<>" is more readable than "<T,v>" as a "I'm a template" declarator
    friend CGenPoly<T,v> foo<>(const CGenPoly<T,v> &p);
};//CGenPoly

template<class T, char v> 
CGenPoly<T,v> foo(const CGenPoly<T,v> &p)
{
    return CGenPoly<T,v>();
}//foo

int main()
{
    CGenPoly<int, 'a'> test;
    cout << test << 1 + test << 1 * test << foo(test) << endl;
    return 0;
}//main

gg

[Paul McKenzie]

Paul,

how low is the precedence of the Operator ^?

is it even lower than +?

Yes.

http://www.cppreference.com/wiki/operator_precedence

what if I try it like that: "(x+1)^3"

And what if I did this?

"x-1^3"

Whatever you come up with, there is another that doesn't work. Basically, operator ^ cannot be used for powers, because it is easily broken with a simple mathematical expression. Operator ^ is a bitwise operator, not a mathematical operator. Using it for math operations is not what it's intended for.

Regards,

Paul McKenzie