#include // printf #include // bool for _Bool and true for 1
#include "stdlib.h" // for rand()
#include "math.h"
/* event array and enum below must be in sync! */
enum state_codes { _idle=0, _goingUp=1, _goingDown=2, _AtTop=3, _AtBottom=4, _malfunction=5, _unexpected=6, _end=7 };
enum ret_codes { up=0, down=1, halt=2, top=3, bottom=4, fail=5, quit=6 };
enum state_codes x = _idle;
int target_floor_number = 8;
int current_floor_number = 1;
int accumulated_floor_number = 0;
#define TOP_FLOOR 9
#define BOTTOM_FLOOR 1
int event_idle(void){
printf("Idle!\n");
printf("Input target floor number in [1, 9] (which floor you want to go?): \n");
target_floor_number = getc(stdin) - '0';
if(current_floor_number < target_floor_number)
return up;
else if(current_floor_number > target_floor_number)
return down;
else if(current_floor_number == target_floor_number)
return halt;
}
int event_goingUp(void){
current_floor_number += 1;
accumulated_floor_number += 1;
printf("Going up! Floor number is %d\n", current_floor_number);
if(accumulated_floor_number > 100)
return fail;
else if(TOP_FLOOR == current_floor_number)
return top;
else if(BOTTOM_FLOOR == current_floor_number)
return bottom;
else if(current_floor_number < target_floor_number)
return up;
else if(current_floor_number == target_floor_number)
return halt;
else
return quit;
}
int event_goingDown(void){
current_floor_number -= 1;
accumulated_floor_number += 1;
printf("Going down! Floor number is %d\n", current_floor_number);
if(accumulated_floor_number > 100)
return fail;
else if(TOP_FLOOR == current_floor_number)
return top;
else if(BOTTOM_FLOOR == current_floor_number)
return bottom;
else if(current_floor_number > target_floor_number)
return down;
else if(current_floor_number == target_floor_number)
return halt;
else
return quit;
}
int event_atTop(void){
printf("At top! current_floor_number= %d\n", current_floor_number);
printf("Input target floor number in [1, 9] (which floor you want to go?): \n");
target_floor_number = getc(stdin) - '0';
if(current_floor_number > target_floor_number)
return down;
else if(current_floor_number == target_floor_number)
return halt;
}
int event_atBottom(void){
printf("At Bottom! current_floor_number= %d\n", current_floor_number);
printf("Input target floor number in [1, 9] (which floor you want to go?): \n");
target_floor_number = getc(stdin) - '0';
if(current_floor_number < target_floor_number)
return up;
else if(current_floor_number == target_floor_number)
return halt;}
int event_malfunction(void){
printf("Elevator needs maintanence!\n");
printf("accumulated_floor_number = %d\n", accumulated_floor_number);
return quit;
}
int event_end(void){
printf("Exit!");
return 0;
}
int event_unexpected(void){
printf("Debug.");
return quit;
}
int (* event[])(void) = { event_idle, event_goingUp, event_goingDown, event_atTop, event_atBottom, event_malfunction, event_unexpected, event_end };
// Nice, thanks for this. The only thing possible flaw here is that the lookup_transitions will likely be linear (O(n)) with this transition table datastructure. Its possible to make it better with multidimentional array - guaranteed O(1). Eg. the table can be represented as a multidimentional array where key is state and the value is an array where the key is the return code and value is the next state: int state_transitions[][3] = { [entry] = { foo, end, foo }, ... } /* ok, fail, repeat */
int lookup_transitions[][7] = {
// return codes:
// up down halt top bottom fail quit
[_idle] = {_goingUp, _goingDown, _idle, _unexpected, _unexpected, _malfunction, _end},
[_goingUp] = {_goingUp, _unexpected, _idle, _AtTop, _AtBottom, _malfunction, _end},
[_goingDown] = {_unexpected, _goingDown, _idle, _AtTop, _AtBottom, _malfunction, _end},
[_AtTop] = {_unexpected, _goingDown, _AtTop, _unexpected, _unexpected, _malfunction, _end},
[_AtBottom] = {_goingUp, _goingDown, _AtBottom, _unexpected, _unexpected, _malfunction, _end},
[_malfunction] = {_end, _end, _end, _end, _end, _end, _end},
[_unexpected] = {_end, _end, _end, _end, _end, _end, _end}
/* transitions from end state aren't needed */
};
#define ENTRY_STATE _idle
#define END_STATE _end
int main(void)
{
enum state_codes cur_state = ENTRY_STATE;
enum ret_codes rc;
int (* state_func)(void);
printf("Start the elevator!\n");
for (;;) {
state_func = event[cur_state];
rc = state_func();
if (END_STATE == cur_state)
break;
cur_state = lookup_transitions[cur_state][rc];
}
printf("END.");
getc(stdin);
getc(stdin);
getc(stdin);
return 0;
}
