Please, how can I have this kind of logics?

class SomeClass
  public:
    SomeClass ;
    void (*modifier)(int&) {m1};
  private:
    void m1(int& i) {i++;}
    void m2(int& i) {i--;}
    void changer (bool condition) {
      if(condition) {
        modifier=m1;
      } else {
        modifier=m2;
      }
    }

when I try to compile such code, I get

error: cannot convert 'SomeClass::m1' from type 'void (SomeClass::)(int&)' to type 'void (SomeClass::*)(int&)'