SCL Examples
Revision as of 13:37, 20 June 2012 by Hannu Niemisto (talk | contribs) (Created page with "== Eight queens puzzle == <pre> > n = 8 > allPositions = [0..n-1] > possibleNextPositions l = allPositions \\ (l + lq + uq) where m = length l lq = [l!i - (m-i) ...")
Eight queens puzzle
> n = 8
> allPositions = [0..n-1]
> possibleNextPositions l = allPositions \\ (l + lq + uq)
where
m = length l
lq = [l!i - (m-i) | i <- [0..m-1]]
uq = [l!i + (m-i) | i <- [0..m-1]]
> expandSolution l =
x <- possibleNextPositions l
return (l + [x])
> solve k cur = if k == n
then return cur
else expandSolution cur >>= solve (k+1)
> solutions = solve 0 []
> length solutions
> repeatString k (s :: String) = sum [s | x <- [1..k]]
> rowText k = repeatString k "." + "X" + repeatString (n-k-1) "."
> printSolution (l :: [Integer]) =
printString (repeatString n "-")
mapM (printString . rowText) l
> mapM printSolution solutions
