bfq.hs

module Main where

import System.Environment
import qualified RotatingQ as Q
import RotatingQ (Queue)

breadthFirst :: (a -> [a]) -> a -> [a]
breadthFirst b r  =  bf b [r]

bf :: (a -> [a]) -> [a] -> [a]
bf _ []      =  []
bf b (x:xs)  =  x : bf b (xs ++ b x)

bfQ :: (a -> [a]) -> Queue a -> [a]
bfQ b q | Q.isEmpty q  = []
        | otherwise    = x : bfQ b (foldl Q.snoc xs (b x))
            where (x, xs) = (Q.head q, Q.tail q)


main :: IO ()
main = do
    print (Q.queue [1, 2, 3] :: Queue Int)
    [n'] <- map (read :: String -> Int) <$> getArgs
    let f n = [(2 * n) + 1, 2 * (n + 1)]
    print $ last . take n' . bfQ f . Q.queue $ [0..]
    -- print $ last . take n' . bf f $ [0..]