Little uncurry example.

uncurryE.hs

module Main where

------------------------------------------------------------------------------
{- |
    First, define some example functions.
-}
------------------------------------------------------------------------------
foo2 :: Int -> Int -> Int
foo2 a b = a + b
------------------------------------------------------------------------------
foo3 :: Int -> Int -> Int -> Int
foo3 a b c = a + b + c
------------------------------------------------------------------------------
foo4 :: Int -> Int -> Int -> Int -> Int
foo4 a b c d = a + b + c + d
------------------------------------------------------------------------------


------------------------------------------------------------------------------
{- |
    Then, utilities.
-}
------------------------------------------------------------------------------
args :: [a] -> (a, a)
args (x:xs) = (x, xs !! 0)
------------------------------------------------------------------------------
{-| 3 arguments: -}
uncurry3 :: (a -> b -> c -> d) -> (a, b, c) -> d
uncurry3 f (x,y,z) = f x y z
------------------------------------------------------------------------------
args3 :: [a] -> (a, a, a)
args3 (x:y:xs) = (x, y, xs !! 0)
------------------------------------------------------------------------------

------------------------------------------------------------------------------
{-| 4 arguments: -}
uncurry4 :: (a -> b -> c -> d -> e) -> (a, b, c, d) -> e
uncurry4 f (a,b,c,d) = f a b c d
------------------------------------------------------------------------------
args4 :: [a] -> (a, a, a, a)
args4 (x:y:z:xs) = (x, y, z, xs !! 0)
------------------------------------------------------------------------------

------------------------------------------------------------------------------
{- |
    Finally, demonstrate!
-}
main = do
    print $ uncurry foo2 (args [1,2])
    print $ uncurry3 foo3 (args3 [1, 2, 3])
    print $ uncurry4 foo4 (args4 [1, 2, 3, 4])