ERROR: empty-deque ;
: peek-front ( deque -- obj )
- peek-front* [ drop empty-deque ] unless ;
+ peek-front* [ drop throw-empty-deque ] unless ;
: ?peek-front ( deque -- obj/f )
peek-front* [ drop f ] unless ;
: peek-back ( deque -- obj )
- peek-back* [ drop empty-deque ] unless ;
+ peek-back* [ drop throw-empty-deque ] unless ;
: ?peek-back ( deque -- obj/f )
peek-back* [ drop f ] unless ;