Curry: An Integrated Functional Logic Language

unwords :: [String] -> String
unwords ws = if ws==[] then []
else foldr1 (\w s -> w ++ ’ ’:s) ws
-- Reverse the order of all elements in a list
reverse :: [a] -> [a]
reverse = foldl (flip (:)) []
-- Compute the conjunction of a Boolean list
and :: [Bool] -> Bool
and = foldr (&&) True
-- Compute the disjunction of a Boolean list
or :: [Bool] -> Bool
or = foldr (||) False
-- Is there an element in a list satisfying a given predicate?
any :: (a -> Bool) -> [a] -> Bool
any p = or . map p
-- Is a given predicate satisfied by all elements in a list?
all :: (a -> Bool) -> [a] -> Bool
all p = and . map p
-- Element of a list?
elem :: a -> [a] -> Bool
elem x = any (x==)
-- Not element of a list?
notElem :: a -> [a] -> Bool
notElem x = all (x/=)
--- Looks up a key in an association list.
lookup :: a -> [(a,b)] -> Maybe b
lookup _ [] = Nothing
lookup k ((x,y):xys)
| k==x = Just y
| otherwise = lookup k xys
-- Generating arithmetic sequences:
enumFrom :: Int -> [Int] -- [n..]
enumFrom n = n : enumFrom (n+1)
enumFromThen :: Int -> Int -> [Int] -- [n1,n2..]
53