// calling functions

unsigned long timer, interval = 1500; // timing variables in milliseconds
int counter = 0; // a counter
byte functions = 5; // the number of functions available (f0 through f4)

void setup() {
  Serial.begin(115200);
}

void loop() {
  if (millis() - timer > interval) { // program running longer than "interval"
    timer = millis(); // store new "time zero"

    if (counter > functions - 1) { // check counter
      Serial.println(); // new line
      counter = 0; // reset counter
    }

    switch (counter) { // check value
      case (0): { // if 0
          function_0(); // call function
          break; // exit this case
        }
      case (1): {
          function_1();
          break;
        }
      case (2): {
          function_2();
          break;
        }
      case (3): {
          function_3();
          break;
        }
      case (4): {
          function_4();
          break;
        }
      default: break;
    }
    counter++; // increment function counter
  }
}

void function_0() {
  Serial.print("f0 Never ");
}
void function_1() {
  Serial.print("f1 gonna ");
}
void function_2() {
  Serial.print("f2 give ");
}
void function_3() {
  Serial.print("f3 you ");
}
void function_4() {
  Serial.print("f4 up ");
}