最近はじめた
練習でエイトクイーン書いたのでだれかコードレビューしてくれよん
MaybeからListに変換するあたりがどうすんのかよくわかってない
import System.IO
import Control.Applicative
main = do
let e = [[]] >>=putOne >>= putOne >>= putOne >>= putOne >>= putOne >>= putOne >>= putOne >>= putOne
print $ e !! 0
print $ e !! 1
print $ e !! 2
print $ e !! 3
print $ e !! 4
print $ length e
type Positions = [(Int, Int)]
-- put one queen on (x,y)
put :: Positions->Int->Int->Maybe Positions
put poss x y
| canPut poss x y = Just $ (x,y):poss
| otherwise = Nothing
where
canPut poss x y = (inBoard x y) && not (crossAny poss x y)
inBoard x y = all (\x->x `elem` [1..8]) [x,y]
cross pos x y = fst pos == x || snd pos == y || abs (fst pos - x) == abs (snd pos - y)
crossAny poss x y = any (\pos->cross pos x y) poss
-- put one queen on puttable place
putOne :: Positions -> [Positions]
putOne [] = map (:[]) $ (,) <$> [1..8] <*> [1..8]
putOne poss@(pos:_) = let xys = [(x,y) | x<-[1..8], y<-[1..8], x>fst pos || (x == fst pos && y>snd pos)] in
xys >>= (\(x,y)->maybeToList $ put poss x y)
where
maybeToList maybe = case maybe of
Nothing -> []
Just(a) -> [a]