de bruijn index -> number

gistfile1.scm

(define n-0 '(L (L (V 0))))

(define n-1 '(L (L (A (V 1) (V 0)))))

(define n-2 '(L (L (A (V 1) (A (V 1) (V 0))))))

(define n-3 '(L (L (A (V 1) (A (V 1) (A (V 1) (V 0)))))))


(define (unwrap n) (cadr (cadr n)))

(define (V? x) (eq? (car x) 'V))

(define (A? x) (eq? (car x) 'A))

(define (A-expr2 x) (caddr x))

(define (conv- m)
  (cond
   ((V? m) 0)
   ((A? m) (+ (conv- (A-expr2 m)) 1))))

(define (conv n) (conv- (unwrap n)))