Arc Forumnew | comments | leaders | submitlogin
1 point by map 6142 days ago | link | parent

  (def rot ((x . y)) (join y `(,x)))


  (def nqueens (n)
    (withs (r (range 1 n) o (keep odd r) e (keep even r) m (mod n 12))
      (if (pos m '(3 9)) (= m -1))
      (join (if (is m -1) (rot e) e)
        (case m
          2 (join '(3 1) (cut o 3 -1) '(5))
          8 (flat:map rev (pair o))
          -1 (rot:rot o)
          o))))


2 points by cchooper 6142 days ago | link

Instead of (= m -1) you could use (nil! m) and then test it with (no m). That's 2 fewer atoms!

-----

2 points by kens1 6142 days ago | link

Is nil! an Anarki thing? (wipe m) is the Arc expression to set m to nil. (And (assert m) sets m to t. Assert tops my list of confusingly named functions.)

-----

2 points by nex3 6142 days ago | link

No, nil! was just the old name for wipe.

-----

1 point by map 6142 days ago | link

Good idea. But "(nil! m)" gives me an error. After making the other changes you suggested, it occurred to me to combine the two "if" clauses into one.

  (def rot ((x . y)) (join y `(,x)))
  (def nqueens (n)
    (withs (r (range 1 n) o (keep odd r) e (keep even r) m (mod n 12))
      (join (if (pos m '(3 9))(or wipe.m rot.e) e)
        (case m
          2 (flat:list 3 1 (cut o 3 -1) 5)
          8 (flat:map rev pair.o)
          nil (rot:rot o)
          o))))
Edit: used "wipe" as suggested below.

Edit: using "flat:list" for case 2.

Edit: replaced (wipe m) with wipe.m, etc.

-----