points.hs

{-# LANGUAGE BangPatterns #-}
import qualified Data.Vector.Unboxed as V
import System.CPUTime
import Text.Printf

time :: IO t -> IO t
time a = do
    start <- getCPUTime
    v <- a
    end   <- getCPUTime
    let diff = (fromIntegral (end - start)) / (10^12)
    printf "Computation time: %0.3f sec\n" (diff :: Double)
    return v

-- data Point = P {-# UNPACK #-} !Int !Int  deriving Show
type Point = (Int, Int)

-- f :: Int -> Int -> Int -> Int -> V.Vector Point
-- f from_y to_y from_x to_x =
--     let a = V.fromList [(from_x, y) | y <- [from_y .. to_y `div` 2 - 1]]
--         b = V.fromList [(to_x, y) | y <- [to_y `div` 2 .. to_y - 1]]
--     in V.concat [a, b]

-- g :: Int -> Int -> Int -> Int -> V.Vector Point
-- g from_y to_y from_x to_x =
--     let a = V.generate (to_y `div` 2 - from_y) (\y -> P from_x (y+from_y))
--         b = V.generate (to_y - to_y `div` 2)   (\y -> P to_x (y + to_y `div` 2))
--     in V.concat [a, b]

g :: Int -> Int -> Int -> Int -> V.Vector Point
g from_y to_y from_x to_x =
    let a = V.generate (to_y `div` 2 - from_y) (\y -> (from_x, y+from_y))
        b = V.generate (to_y - to_y `div` 2)   (\y -> (to_x, y + to_y `div` 2))
    in V.concat [a, b]


main = time $
    let v = g 20000000 80000000 1 2
    in print (V.last v)