gistfile1.hs

-- medidor de beat
-- compilar: 'ghc --make beat.hs'
-- cuenta distancias en milisegundos entre clicks de teclado
-- salir con 'q'

import qualified Graphics.UI.SDL as SDL
import Graphics.UI.SDL.Keysym as K
import Graphics.UI.SDL.Time as T

import Data.Word(Word32)

avg :: [Word32] -> Word32
avg xs = round (suma / longitud) where
    suma = fromIntegral $ sum xs
    longitud = fromIntegral $ length xs

avg_integral :: [Word32] -> Word32
avg_integral xs = snd par where
    margen = 50
    promedio = avg xs
    rango = [(promedio - margen)..(promedio + margen)]
    f x = abs $ sum $ zipWith (-) xs (repeat x)
    par = minimum $ zip (map f rango) rango

main :: IO [Word32]
main = do
    SDL.init []
    SDL.setVideoMode 640 480 24 []
    xs <- eventLoop []
    SDL.quit
    let ys = zipWith (-) (tail xs) (drop 2 xs)
    print ys
    print $ avg_integral ys
    return xs
    where
    eventLoop :: [Word32] -> IO [Word32]
    eventLoop ys = SDL.waitEventBlocking >>= checkEvent ys
    checkEvent :: [Word32] -> SDL.Event -> IO [Word32]
    checkEvent ys (SDL.KeyDown (Keysym {symKey = K.SDLK_q})) = return ys
    checkEvent ys (SDL.KeyDown _) = T.getTicks >>= (\k -> eventLoop (k:ys))
    checkEvent ys _ = eventLoop ys