valvallow

(define atom? 
  (lambda (x) 
    (and (not (pair? x)) 
         (not (null? x)))))

(define add1 
  (lambda (n) 
    (+ n 1)))

(define sub1 

valvallow

;; let loop
(let loop ((s 0))
           (if (< s 10)
               (begin
                 (print "hello")
                        (loop (+ 1 s)))))

;; for-each
(use srfi-1)
(for-each

valvallow

(((lambda (f) 
    (f f)) 
  (lambda (f) 
    (lambda (n) 
      (if (<= n 100)
          (begipn
            (print (cond
                    ((zero? (modulo n 15)) "FizzBuzz")
                    ((zero? (modulo n 5)) "Buzz")
                    ((zero? (modulo n 3)) "Fizz")

valvallow

(define fact
  (lambda (n)
    (if (zero? n)
        1
        (* n (fact (- n 1))))))
(fact 5)

;; apply
(use srfi-1)
(define fact

valvallow

(use srfi-1)
(define 9x9
  (lambda (row cnt inc mul)
    (append
     (cons
      (map (lambda (n)
            (cons (cons mul n)(cons (* n mul) '())))
           (iota cnt 1 inc))
      (if (zero? row)
          '()

valvallow

(define combination
  (lambda (r l)
    (cond
     ((null? l) '())
     ((or (zero? r)(> r (length l))) '())
     ((= r 1)(map list l))
     ((= r (length l))(list l))
     (else (append (map (lambda (n)(cons (car l) n))
                        (combination (- r 1)(cdr l)))
                   (combination r (cdr l)))))))

valvallow

(define date->gmt
  (lambda (date)
    (let ((g (lambda (ls dl)
               (string-join
                (map (lambda (f)
                       (format #f "~2,,,'0,@a" (f date))) ls) dl))))
      (let ((yyyyMMdd (g (list date-year date-month date-day) "-"))
            (hhmmdd (format #f "T~aZ"
                            (g (list date-hour date-minute date-second) ":"))))
        (string-append yyyyMMdd hhmmdd)))))

valvallow

(define make-pad
  (lambda (c len)
    (lambda (n)
      (format #f (string-append "~" (number->string len) ",,,'" c ",@a") n))))

valvallow

(map (lambda (f)
       (f 5 5))
     (list * + - /))
; -> (25 10 0 1)

(map (lambda (f)
       (f 5 5))
     '(* + - /))
; -> error

valvallow

((lambda (f)
   (f f 10))
 (lambda (f n)
   (if (< 0 n)
       (begin
         (print n)
         (f f (- n 1))))))
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