Unnamed

(define (find-route orig dest G)
  (local ((define (neighbours v G)
            (cond
              [(empty? G) (error 'neighbours (string-append (symbol->string v) " not in graph"))]
              [else
               (cond
                 [(symbol=? v (first (first G))) (second (first G))]
                 [else (neighbours v (rest G))])]))
          (define (find-route-helper orig dest seen still-to-visit G)
            (cond
              [(and (empty? still-to-visit) (empty? (neighbours orig G))) false]
              [(member dest seen) still-to-visit]
              [(empty? (neighbours orig G)) 
                    (find-route-helper (first still-to-visit)
                                       dest
                                       seen
                                       (second (rest still-to-visit)) G)]
              [else (find-route-helper (first (neighbours orig G))
                                       dest
                                       (append (neighbours orig G) seen)
                                       (append (list (first seen) (rest (neighbours orig G))) (list still-to-visit))
                                       G)])))
  (find-route-helper orig dest (list orig) empty G)))

(define testGraph '((A (B1 B2)) (B1 (C)) (B2 (C)) (C (D1 D2)) (D1 (E)) (D2 (E)) (E ()) (F ()))) 
(equal? (find-route 'A 'F testGraph) false)
(equal? (find-route 'A 'C testGraph) '(A B1 C))