Creating a finite state machine in C language

 Finite state machine implementation in C

This is an implementation of FSM in C as you can see there are 3 functions named
cheese_day(),grapes_day() & lettuce_day() which represents the state/nodes
fsm is an array of pointers to function, which is used to access the functions
i.e. void (*fsm[])()= { cheese_day , grapes_day, lettuce_day };Now we are using the index of the fsm to jump to the specific function
i.e. fsm[input_symbol]();

1. #include <cstdio>
2. #include <cstdlib>
3. #include <cstring>
4. #define IM_STARVING 0
5. #define LETS_GO_SHOPPING 0
6. #define ILL_HAVE_CHEESE_TOMMORROW 1
7. #define ILL_HAVE_LETTUCE_TOMMORROW 2
8. #define ILL_HAVE_GRAPES_TOMMORROW 3
9. int inp[5]= {ILL_HAVE_CHEESE_TOMMORROW ,ILL_HAVE_LETTUCE_TOMMORROW,ILL_HAVE_CHEESE_TOMMORROW,ILL_HAVE_GRAPES_TOMMORROW,IM_STARVING};  // automated Input!
10. void cheese_day()
11. {
12.   printf("state :- cheese day\n");
13. }
14. void grapes_day()
15. {
16.   printf("state :- grapes day\n");
17. }
18. void lettuce_day()
19. {
20.   printf("state :- lettuce day\n");
21. }
22. void (*fsm[])()= { cheese_day , grapes_day, lettuce_day };
23. int main()
24. { int j=0;
25.   while(j< 5)
26.   { int input_symbol=inp[j++];
27.    switch(input_symbol) {
28.     case 1:
29.     input_symbol=ILL_HAVE_CHEESE_TOMMORROW - 1;
30.     fsm[input_symbol]();
31.     break;
32.     case 2:
33.     input_symbol=ILL_HAVE_LETTUCE_TOMMORROW - 1;
34.     fsm[input_symbol]();
35.     break;
36.     case 3:
37.     input_symbol=ILL_HAVE_GRAPES_TOMMORROW - 1;
38.     fsm[input_symbol]();
39.     break;
40.     default:
41.     fsm[input_symbol]();
42.    }
43.   }
44.  return 0;
45. }