Hofstadter Figure-Figure sequences: Difference between revisions

=={{header|EchoLisp}}==

<lang scheme>

(define (FFR n)

(+ (FFR (1- n)) (FFS (1- n))))

(define (FFS n)

(define next (1+ (FFS (1- n))))

(for ((k (in-naturals next)))

#:break (not (vector-search* k (cache 'FFR))) => k

))

(remember 'FFR #(0 1)) ;; init cache

(remember 'FFS #(0 2))

</lang>

{{out}}

<lang scheme>

(define-macro m-range [a .. b] (range a (1+ b)))

(map FFR [1 .. 10])

→ (1 3 7 12 18 26 35 45 56 69)

;; checking

(equal? [1 .. 1000] (list-sort < (append (map FFR [1 .. 40]) (map FFS [1 .. 960]))))

→ #t

</lang>