c++ - Why this class doesn't make error? -

#include <iostream> using namespace std;  class item{ private:     int cnt;  public:     item(){}      void func(item a){         a.cnt = 10;     } };  int main(){     return 0; } 

i assume red line make error. because 'a.cnt' value private value. learned private value must modified inner of class.

void func(a a){     a.cnt = 10; //valid } 

notice function inside class, becomes member , class member functions have access private members.

note being modified inner of class item using member function,which valid