Splitting task among several functions

I am looking for 开发者_开发问答something which enables me to do something like a function in a function. Here is an example to make it more obvious:

class A{
 private: 
 int n;
 int c;
 public:
 void foo();
}

However foo is a function with is supposed to change c, but needs n for that. foo is somewhat complicated so I want to split it into different subfunctions. Since foo needs n it is not simple doable through a friend function (without passing n (there are tons of variables in my real problem)

Just put all those sub-functions inside the same class and make them private?

class A
{
    int n;
    int c;
    void foo_thing_1();
    void foo_thing_2();
public:
    void foo() { foo_thing_1(); foo_thing_2(); }
};

As it was pointed by other answers already, simple private functions should suffice - unless you also need acess to original function internal variables - which in c++11 is not possible. In upcoming c++0x you might want to look at lambda functions - though i am sure that's not what they were meant for.