C++ redefinition

I am trying to implement a function class, but got a error of redefinition. I 开发者_开发知识库know it is stupid, but can anyone please help?

=== header file ===

#ifndef _NS4_h
#define _NS4_h

#include <vector>
#include <list>

namespace NS4{
    class complex{
    double r, i;
    public:
        complex(double a=0, double b=0) : r(a), i(b) {};    
        complex operator+(complex c);
        complex &operator+=(complex c);
        complex &operator=(complex c);
    };

    // function class 
    class Add{      
        complex val;
    public:
        Add(complex c){ val = c; }
        Add(double r, double i) { val = complex(r, i); }
        void operator()(complex& c) const { c += val; } 
    };

    void h(std::vector<complex> &aa, std::list<complex> ll, complex z);
}
#endif 

=== Part of the cpp file ===

using namespace NS4;
void test9()
{

    vector<complex> aa;
    aa.push_back(complex(0,1));
    aa.push_back(complex(0,2));
    aa.push_back(complex(0,3));

    list<complex> ll;
    ll.push_back(complex(1,1));
    ll.push_back(complex(1,2));
    ll.push_back(complex(1,3));

    complex zz(1,1);

    // the following line is not working
    // error C2371: 'zz' : redefinition; different basic types
    Add(zz);  // Add(complex(1,1)) is working.

    h(aa,ll, zz);
}

You have an Add class, so you need to create an instance of it, in order to call the constructor.

So in the below case, a is an instance of our Add class.

Add a(zz);

You can optionally put parenthesis around the variable name in a declaration.

int (i);

is the same as

int i;

So in your case you are declaring a variable named zz of type Add, and a variable named zz already exists. You probably meant to pass zz as an argument to Add constructor, but then you should give some name to the variable:

Add adder(zz);

However, I don't see where that instance is used at all.

But if you just want to invoke the constructor of Add without declaring a variable, you can put parenthesis around the whole expression:

(Add(zz)); //just calls Add::Add(Complex);

Welcome to C++ ;)

What is Add(zz) supposed to mean? What do you think it means?

Add(zz) is actually a declaration of object zz of type Add, i.e.

Add(zz);

is equivalent to

Add zz;

You have already defined zz before, which is why you get the redefinition error. No surprise here.

There's no way to help you further without knowing what you were trying to do by that Add(zz) line.