Question

Learning C++ and see the class laid out like this:

class CRectangle {
    int x, y;
  public:
    void set_values (int,int);
    int area () {return (x*y);}
};

void CRectangle::set_values (int a, int b) {
  x = a;
  y = b;
}

I know Java and methods(functions) in Java are written within the class. The class looks like a Java interface. I know I can write the class like this:

class CRectangle {
    int x, y;
  public:
    void set_values (int a, int b) {
      x = a;
      y = b;
    };
    int area () {return (x*y);}
};

But is there a difference or standard?

Answer 1

There’s a difference. When you write the definition of the function within the class definition (case 2), then the function is considered to have been declared inline. This is standard C++.

Usage, is to declare the member functions (Java methods) within the class definition, in a header file (.h), and to define these member functions in a C++ file (.cpp, .cc, or .C, …) This reduces compilation time, when you change the body of a function, only the C++ file has to be compiled, whereas if you change something in the header file, all C++ files that include this header are to be compiled.