Question

Possible Duplicate:
Code convert from C++ to C
Converting a C++ class to a C struct (and beyond)

I used to be a C++ programmer, but now I need to write a program in C.
e.g. in C++

Main.cpp
=====================
int main
{
  ns::Sum sum(1, 2);
}

Sum.h
=====================
namespace ns
{
  class Sum
  {
    public:
    Sum(int a, int b);
    private:
    void AddThemUp();
    int a;
    int b;
  }
}

Sum.cpp
======================
namespace ns
{
  Sum::Sum(int a, int b)
  {
    this->a = a;
    this->b = b;
    AddThemUp();
  }

  void Sum::AddThemUp()
  {
     a + b;//stupid for returning nothing, just for instance
  }
}

That’s in C++
I don’t know how to put above in C. because there is no class there.
if I declare data member a & b in header file, they will become global variables.
I don’t like global variables. and is there namespace in C?
who can help? thank you

Answer 1

Here is a simple conversion from C++ to C. This method allows for stack objects, like how you use ns::Sum. As a note, you should also have a release function that cleans up any memory allocated by the structure.

// Main.c
// =====================

// Construction
ns_Sum sum;
ns_SumInitWithAAndB(&sum, 1, 2);

// Sum.h
// =====================

// All member variables are contained within a struct
typedef struct ns_Sum_
{
    int a;
    int b;
} ns_Sum;

// Public Methods
void ns_SumInitWithAAndB(ns_Sum *sum, int a, int b);

// Sum.c
// ======================

// Private Methods can be declared as static functions within the .c file
static void ns_SumAddThemUp(ns_Sum *sum);

void ns_SumInitWithAAndB(ns_Sum *sum, int a, int b)
{
    sum->a = a;
    sum->b = b;
    ns_SumAddThemUp(sum);
}

void ns_SumAddThemUp(ns_Sum *sum)
{
    a + b; //stupid for returning nothing, just for instance
}