root/lang/ruby/nendo/trunk/init.nnd @ 32307

;;-*- mode: scheme; syntax: scheme -*-;;

;; ruby's p like function.
(define p
  (lambda (x)
    (printf "%s\n" x)
    x))

;; ----------------------------------------
;; Higher-order functions
;; ----------------------------------------
(define map
  (lambda (pred lst)
    (if (null? lst)
        '()
        (cons
         (pred (car lst))
         (map pred (cdr lst))))))
(define foreach map)

(define filter
  (lambda (pred lst)
    (if (null? lst)
        '()
        (let ((result  (pred (car lst))))
          (if result
              (cons
               result
               (filter pred (cdr lst)))
              (filter pred (cdr lst)))))))


;; ----------------------------------------
;; List Utility functions
;; ----------------------------------------
  

;;(define (iota num)
;;  (begin
;;    (def _iota
;;         (lambda
;;             (num)
;;           
;;           (if (<= num 0)
;;               '()
;;               (cons
;;                num            
;;                (_iota (- num 1))))))
;;    (reverse (_iota (num))))))



;; test code
;; (filter pass '(1))
;; (filter pass '(1 2 true false nil 3 a b c)))

;; ----------------------------------------
;; Utility function for testing
;; ----------------------------------------
;; pass through the argument value as return value.
(define pass
  (lambda (x)
    x))