すごいH本読書会 in 大阪#2の練習問題を解いた

sugoi2.hs

import Data.Char (toUpper, intToDigit)
import Data.List (concat, words, tails, isPrefixOf)

upperCase :: String -> String
upperCase = map toUpper

removeSpace :: String -> String
removeSpace = concat . words

cover :: Eq a => [a] -> [a] -> Bool
cover lst1 lst2 = foldr (\x acc -> if (lst1 `isPrefixOf` x) then True else acc) False $ tails lst2

uniq :: Eq a => [a] -> [a]
uniq = foldr (\x acc -> if (x `elem` acc) then acc else x:acc) []

binExp :: (Integral a, Show a) => a -> String
binExp 0 = intToDigit 0:[]
binExp 1 = intToDigit 1:[]
binExp n = (binExp $ n `div` 2) ++ (show $ n `mod` 2)

main = do
    print $ upperCase "Hello World"
    print $ removeSpace "Hello World\nI'm John."
    print $ [2..4] `cover` [1..4]
    print $ [2..6] `cover` [1..4]
    print $ uniq [1, 2, 1, 7, 6, 2, 4, 8]
    print $ binExp 10