+ var new_index = input_index;
+ while (true) {
+ var next = new_index + direction;
+ if (next < 0) {
+ say("At beginning");
+ return;
+ }
+ if (next >= files.length) {
+ say("At end");
+ return;
+ }
+ new_index = next;
+ if (filter(new_index)) {
+ break;
+ }
+ }
+ input_index = new_index;