State Machines

// from http://c-faq.com/decl/recurfuncp.html
// Mod by JDN
// Simple efficent way to model state machines in C


#include <stdio.h>

typedef void *(*pFunc)(); // for typecast for calling function

// States -- you need this forward dcl for the compiler and calling

// led-off --> led-on ---|
//   ^-------------------|
// all driven from main (or here setup fct)

void *led_on();  // as name indicates ...
void *led_off();

void *led_on() {
  printf("on\n");
  return (void *)led_off; // next state
}

void *led_off() {
   printf("off \n");
   return (void *)led_on; // next state
}


void main() {

  pFunc statefunc = led_on, oldfunc = led_on;

  while(1) {
    oldfunc = statefunc;  // if you want to see the previous state  - line can be omitted
    statefunc = (pFunc)(*statefunc)();
     // nice thing of design is you can easily track all state changes bq you will pass by here :-)
  }

  return ; // should not get here
}

// from http://c-faq.com/decl/recurfuncp.html
// Mod by JDN for Arduino
//
// Simple efficent way to model state machines in C

typedef void *(*pFunc)(); // for typecast for calling function

// States -- you need this forward dcl for the compiler and calling

// led-off --> led-on ---|
//   ^-------------------|
// all driven from main (or here setup fct)

void *led_on();  // as name indicates ...
void *led_off();

void *led_on() {
  digitalWrite(13,HIGH);
  delay(1000); // sleep for a second

  return (void *)led_off; // next state
}

void *led_off() {
  digitalWrite(13,LOW);
  delay(1000); // sleep for a second

  return (void *)led_on; // next state
}


void setup() {


  pinMode(13,OUTPUT);

}

pFunc statefunc = led_on, oldfunc = led_on;


/*
* The idea
* Variable named statefunc(aka state) holds address of next function to be called
* when you leave a function you simply return reference to enxt function or state to be called
* This address is stored in variable statefunc.
* The code loops and call again and now we call next state
* Instead of having code in loop you could have it every where like

* while (1) {
*   oldfunc = statefunc;  // just if you want to see the previous state     - debugging !!!
*   statefunc = (pFunc)(*statefunc)();
* }
*
*/
void loop() {
   oldfunc = statefunc;  // just if you want to see the previous state     - debugging !!!
   statefunc = (pFunc)(*statefunc)();
}