import "Prelude" hiding (findFirst)

infinity = 1e9

@inline
findFirst :: (a -> <e> Maybe b) -> [a] -> <e> Maybe b
findFirst f l = loop 0
  where
    len = length l
    loop i                         
        | i >= len  = Nothing
        | otherwise = match f (l!i) with
                        s @ (Just _) -> s
                        Nothing      -> loop (i+1)

dfsFirst :: (a -> <e> Boolean) -> (a -> <e> [a]) -> [a] -> <e> (Maybe a)
dfsFirst acceptable successors initial = tryAll initial
  where
    tryAll l = findFirst loop l
    loop p 
        | acceptable p = Just p
        | otherwise    = tryAll (successors p)

data Weighted a = Weighted a Double

//type SearchAlgorithm e a =
//    (a -> <e> Boolean) -> (a -> <e> [Weighted a]) -> [Weighted a] -> <e> Weighted (Maybe a)
    
//dfs :: SearchAlgorithm e a
dfs :: (a -> <e> Boolean) -> (a -> <e> [Weighted a]) -> [Weighted a] -> <e> Weighted (Maybe a)
dfs acceptable successors initial = foldl loop (Weighted Nothing infinity) initial
  where
    loop best@(Weighted _ bestW) (Weighted p w)
        | w >= bestW   = best
        | acceptable p = Weighted (Just p) w
        | otherwise    = foldl loop best
                       $ map (\(Weighted p' w') -> Weighted p' (w+w'))
                       $ successors p

/*
bfs :: SearchAlgorithm e a

aStar :: (a -> <e> Double) -> SearchAlgorithm e a
*/
main = "Hello"
--
Hello