small calculation reduction

kern/synchprobs/traffic_synch.c

@@ -56,14 +56,9 @@ static void push(car * newcar)
 }
 
 // called when a car clears the intersection
-static void clearint(car * done)
+static void clearint(car * done, int pos)
 {
-  // dirs + origin is our offset for where to start in the array
-  // compass + origin is the array we use to determine what to add to the first number
-  // newcar->dest gives the direction, which we use to find the offset indicating it's additive value
-  // set the array of active cars to null at this value
-  int total = dirs[done->origin] + *(compass[done->origin] + done->dest);
-  active[total] = NULL;
+  active[pos] = NULL;
   
   if (done->cv) // if this car was blocking something
   {
@@ -173,6 +168,6 @@ void intersection_after_exit(Direction origin, Direction destination)
 {
   lock_acquire(globlock);
   int position = dirs[origin] + *(compass[origin] + destination);
-  clearint(active[position]);
+  clearint(active[position], position);
   lock_release(globlock);
 }