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Joined 2026-09-21 Message
Incoming links: Uncurrying
Curried function 2026-10-31
In functional programming, currying represents a function of several arguments as successive one-argument functions. In Haskell, arrows associate to the right:
a -> b -> c means a -> (b -> c). Supplying an argument of type a therefore returns a function of type b -> c, while a function of type (a,b) -> c expects a tuple. Uncurrying converts the first representation to the second.The map function changes each element of a list while preserving its order and length. List concatenation removes one level of nesting. Currying changes a function on a pair into a function taking its two arguments separately; uncurrying reverses this conversion:
map :: (a -> b) -> [a] -> [b]
map f [] = []
map f (x:xs) = f x : map f xs
concat :: [[a]] -> [a]
concat [] = []
concat (xs:xss) = xs ++ concat xss
curry :: ((a, b) -> c) -> a -> b -> c
curry f x y = f (x, y)
uncurry :: (a -> b -> c) -> (a, b) -> c
uncurry f (x, y) = f x yThese polymorphic type signatures impose no numerical, equality or ordering constraints: the definitions only inspect list or pair structure and apply a supplied function. In particular,The recursive equations describe the two possible list constructors, so they also explain how the empty case terminates each finite computation.
infixr 9 .
(.) :: (b -> c) -> (a -> b) -> a -> c
(f . g) x = f (g x)
zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
zipWith f (x:xs) (y:ys) = f x y : zipWith f xs ys
zipWith _ _ _ = []
uncurry :: (a -> b -> c) -> (a,b) -> c
uncurry f (x,y) = f x yFunction composition passes the result of the second function into the first.
zipWith combines corresponding list elements and stops when either list ends. Uncurrying converts a function taking two successive arguments into one taking a pair. None of these operations needs a numeric or ordering constraint.