すごいHaskell読書会の演習

gread_haskell_no1.hs

slice :: Int -> Int -> [a] -> [a]
slice i j [] = []
slice i j all@(x:xs)
  | i < 0  = slice 0 j all
  | i > j  = []
  | i == 0 = take j all
  | i > 0  = slice (i-1) (j-1) xs

fib :: Int -> Int
fib 1 = 1
fib 2 = 1
fib n
  | n <= 0    = error "not defined"
  | otherwise = fib(n-1) + fib(n-2)

fizzBuzz :: Int -> Int -> [String]
fizzBuzz n m = [ fb x | x <- [n..m]]
  where fb x
          | x `mod` 15 == 0 = "FizzBuzz"
          | x `mod`  5 == 0 = "Buzz"
          | x `mod`  3 == 0 = "Fizz"
          | otherwise       = show x

goodNum :: Int -> Bool
goodNum x
  | x < 100   = False
  | x > 999   = False
  | otherwise = (x `mod` sum1 x == 0) && (x `mod` sum2 x == 0)
  where sum1 x = (x `div` 10) + (x `mod` 10)
        sum2 x = (x `div` 100) + (x `mod` 100)
goodNums = take 4 [x | x <- [100..], x `mod` 10 /= 0, goodNum x]