Arc Forumnew | comments | leaders | submitlogin
2 points by almkglor 6046 days ago | link | parent

Here's a version that can actually be compiled by arc2c:

  (def prsall (rest)
    (if rest
      (do (pr (car rest) #\space)
          (prsall:cdr rest))))

  (def map (f l)
    (if l
      (cons (f:car l) (map f (cdr l)))))

  (def factorial (n)
    (if (> n 0)
        (* n (factorial (- n 1)))
        1))

  (def choose (n k)
    ; arc2c only supports two-arg forms for math
    (/ (/ (factorial n) (factorial k))
       (factorial (- n k))))

  (def indices (n)
    (let self nil
      ; no support for '= yet
      (set self
        (fn (i)
          (if (isnt i n)
              (cons i (self (+ i 1))))))
      (self 0)))

  (def pascal-triangle (n)
    (let self nil
      (set self
        (fn (i)
          (if (<= i n)
              (do
                ; Anarki make-br-fn not supported yet
                (prsall (map (fn (_) (mod (choose i _) 2)) (indices (+ i 1))))
                (prn)
                (self (+ i 1))))))
      (self 0)))

  (pascal-trangle 4)
If you're feeling particularly nasty, you can get the C output from arc2c and pass that ^^