How to change local static variable value from outside function

Question

#include 

void func() {
   static int x = 0;  // x is initialized only once across three calls of
                      //     func()
   printf(\"%d\\n\"         


        

Answer 1

Do you want the function always to reset the counter after three invocations? or do you want to the caller to reset the count at arbitrary times?

If it is the former, you can do it like this:

void func() {
  static int x = 0;
  printf("%d\n", x);
  x = (x + 1) % 3;
}

If it is the latter, using a local static variable is probably a bad choice; you could instead use the following design:

class Func
{
  int x;
  // disable copying

public:
  Func() : x(0) {}

  void operator() {
    printf("%d\n", x);
    x = x + 1;
  }

  void reset() {
    x = 0;
  }
};

Func func;

You should make it either non-copyable to avoid two objects increasing two different counters (or make it a singleton), or make the counter a static member, so that every object increments the same counter. Now you use it like this:

int main(int argc, char * const argv[]) {
  func(); // prints 0
  func(); // prints 1
  func(); // prints 2

  func.reset();
  return 0;
}