rotate a matrix 90 degrees to the right in scheme

rotate90.scm

(define (transpose m)
  (apply map list m))

(define (rotate-90 m)
  (transpose (reverse m)))

(define matrix
  (list (list 'a 'b 'c 'd)
        (list 'e 'f 'g 'h)
        (list 'i 'j 'k 'l)
        (list 'm 'n 'o 'p)))

(define rotated-matrix
  (list (list 'm 'i 'e 'a)
        (list 'n 'j 'f 'b)
        (list 'o 'k 'g 'c)
        (list 'p 'l 'h 'd)))

(equal? (rotate-90 matrix) rotated-matrix))