Simple perceptron train in Haskell.

perceptron.hs

type Vector = (Double, Double)


dotV :: Vector -> Vector -> Double
dotV (x, y) (u, v) = x * u + y * v


addV :: Vector -> Vector -> Vector
addV (x, y) (u, v) = (x + u, y + v)


negV :: Vector -> Vector
negV (x, y) = (-x, -y)


predict :: Vector -> Vector -> Int
predict xy uv | dotV xy uv > 0 =  1
              | otherwise      = -1


predictAll :: Vector -> [Vector] -> [Int]
predictAll xy = map $ predict xy


trainOnce :: Vector -> Vector -> Int -> Vector
trainOnce xy uv z | z == predict xy uv = xy
                  | z == 1             = addV xy uv
                  | otherwise          = addV xy (negV uv)


train :: Vector -> [(Vector,Int)] -> Vector
train = foldl $ \xy (uv,z) -> trainOnce xy uv z


getPerceptron :: IO (Vector, Int)
getPerceptron = do
    raw <- getLine
    let [u,v] = take 2 $ map read $ words raw
        z     = read $ last $ words raw
    return ((u,v),z)


main :: IO ()
main = do
    rn <- getLine
    ls <- sequence $ replicate (read rn) getPerceptron 
    print $ train (0,0) ls