2012 Start Haskell#2 http://wiki.haskell.jp/Workshop/StartHaskell/LYHGG/exercise/3

exercise.hs

{-# OPTIONS -Wall #-}

-- Not,And,Or,Xor を独自実装
myAnd :: Bool -> Bool -> Bool
myAnd True True = True
myAnd _ _ = False

myNot :: Bool -> Bool
myNot False = True
myNot _ = False

myOr :: Bool -> Bool -> Bool
myOr True False = True
myOr False True = True
myOr True True = True
myOr _ _ = False

myXor :: Bool -> Bool -> Bool
myXor True False = True
myXor False True = True
myXor _ _ = False

-- うるう年判定
isLeap :: Int -> Bool
isLeap i
    | i `mod` 400 == 0 = True
    | i `mod` 100 == 0 = False
    | i `mod` 4 == 0 = True
    | otherwise = False

-- FizzBuzz
fizzBuzz :: Int -> String
fizzBuzz x
    | x `mod` 15 == 0 = "FizzBuzz"
    | x `mod` 3 == 0 = "Fizz"
    | x `mod` 5 == 0 = "Buzz"
    | otherwise  = show x

-- 文字列解析
analysisLine :: String -> String
analysisLine [] = "empty"
analysisLine [_] = "a character"
analysisLine s'
    | last s' == '.' = "a sentence"
    | ' ' `elem` s' = "some words"
    | otherwise = "a word"

-- cancat を独自実装
concatR :: [[a]] -> [a]
concatR = foldr (++) []

concatL :: [[a]] -> [a]
concatL = foldl (++) []

-- シーザー暗号化
caesarSucc :: Char -> Char
caesarSucc 'z' = 'a'
caesarSucc 'Z' = 'A'
caesarSucc ' ' = ' '
caesarSucc c = succ c

caesar :: Int -> String -> String
caesar 0 s = s
caesar i s = caesar (i-1) . map caesarSucc $ s

-- シーザー複合化
caesarPred :: Char -> Char
caesarPred 'a' = 'z'
caesarPred 'A' = 'Z'
caesarPred ' ' = ' '
caesarPred c = pred c

caesarComposite :: Int -> String -> String
caesarComposite 0 s = s
caesarComposite i s = caesarComposite (i-1) . map caesarPred $ s