There are two orthogonal errors going on here:
1. You need to use auto to embed constants. See the comments at the code
below on how to use it.
2. You need to wrap [Matrix a] in a newtype. grad requires you to
provide a function f a -> a, however sc2 _ has the type [Matrix a] -> a
so if you replace [] by f you end up with f (Matrix a) -> a which
results in the error you’re seeing.
Miguel A. Santos
mv _ [] = [] mv (M []) _ = [] mv ( M m ) v = ( dot (head m) v ) : (mv (M (tail m)) v ) --- two matrices
You need explicit type annotations to make this polymorphic here because of the monomorphism restriction. mbW1 :: Num a => Matrix a
mbW1 = M $ [[1,0,0],[-1,5,1],[1,2,-3]] mbW2 = M $ [[0,0,0],[1,3,-1],[-2,4,6]] --- two different scoring functions
-- Provide a type signature and map auto over the constants sc1 :: (Floating b, Mode b) => [Scalar b] -> Matrix b -> b sc1 v m = foldr (+) 0 $ (phi' . (mv m) ) (map auto v) -- Provide a type signature, use auto and use the newtype newtype MatrixList a = MatrixList [Matrix a] deriving (Functor,Foldable,Traversable) sc2 :: (Floating a,Mode a) => [Scalar a] -> MatrixList a -> a sc2 v [m1, m2] = foldr (+) 0 $ (phi' . (mv m2) . phi' . (mv m1) ) (map auto v)
strToInt = read :: String -> Double strLToIntL = map strToInt--- testing main = do putStrLn $ "mbW1:" ++ (show mbW1) putStrLn $ "mbW2:" ++ (show mbW2) rawInput <- readFile "/dev/stdin" let xin= strLToIntL $ lines rawInput putStrLn "sc xin mbW1"
-- That needs an explicit type annotation because mbW1 is polymorphic print $ sc1 xin (mbW1 :: Matrix Double) --- ok. =
putStrLn "grad (sc1 xin) mbW1" print $ grad ( sc1 xin) mbW1 -- yields an error: expects xin [Reverse s Double] instead of [Double] putStrLn "grad (sc1 [3,5,7]) mbW1" print $ grad ( sc1 [3,5,7]) mbW1 --- ok. = putStrLn "sc2 xin [mbW1,mbW2]" print $ sc2 xin [mbW1, mbW2] putStrLn "grad (sc2 [3,5,7) [mbW1,mbW2]"
-- Use the newtype defined above print $ grad ( sc2 [3,5,7]) (MatrixList [mbW1, mbW2]) --- Error: see text Also as a general recommendation, write your type signatures explicitely at least for top level definitions. Cheers Moritz