-#define PUSH(low, high) ((void) ((top->lo = (low)), (top->hi = (high)), ++top))
-#define POP(low, high) ((void) (--top, (low = top->lo), (high = top->hi)))
-#define STACK_NOT_EMPTY (stack < top)
+#define PUSH(low, high) ((void) ((stack[i].lo = (low)), (stack[i].hi = (high)), i++))
+#define POP(low, high) ((void) (i--, (low = stack[i].lo), (high = stack[i].hi)))