reduce-right-sample.scm

(cond-expand
  (gauche (import (gauche base) (scheme base) (scheme write)))
  (guile  (import (srfi srfi-1)))
  (chibi  (import (srfi 1) (scheme small))))

(define (f x y) (list (list (+ (* (caar   x) (caar   y))
                               (* (cadar  x) (caadr  y)))
                            (+ (* (caar   x) (cadar  y))
                               (* (cadar  x) (cadadr y))))
                      (list (+ (* (caadr  x) (caar   y))
                               (* (cadadr x) (caadr  y)))
                            (+ (* (caadr  x) (cadar  y))
                               (* (cadadr x) (cadadr y))))))
(define ridentity '((1 0) (0 1)))

(display (f '((10 11) (12 13)) ridentity)) (newline)
;; => ((10 11) (12 13))

(display (list
          (reduce-right f ridentity '())
          (reduce-right f ridentity '(((2 3) (4 5))))
          (reduce-right f ridentity '(((2 3) (4 5)) ((6 7) (8 9))))))
(newline)
;; => (((1 0) (0 1)) ((2 3) (4 5)) ((36 41) (64 73)))

かなり原始的な書き方してるのは気にしないで下さい．他の高階関数にあまり依存したくなかったんですよ…（言い訳）．