OFFSET
0,3
COMMENTS
This Catalan bijection rotates binary trees left, if possible, otherwise reflects them with the Catalan bijection A057163.
LINKS
A. Karttunen, Gatomorphisms (with the complete Scheme source)
PROG
(Scheme) ;; Functions implementing this automorphism on list-structures:
(define (gma082335! s) (cond ((pair? s) (cond ((pair? (cdr s)) (robl! s)) (else (gma057163! s))))) s)
(define (robl! s) (let ((ex-car (car s))) (set-car! s (cddr s)) (set-cdr! (cdr s) ex-car) (swap! (cdr s)) (swap! s) s))
(define (swap! s) (let ((ex-car (car s))) (set-car! s (cdr s)) (set-cdr! s ex-car) s))
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 17 2003
STATUS
approved
