めもめも
忘れそうなのでメモだけしちゃいますね☆
import Data.Char import Control.Monad import List import Numeric import Text.Show joinList sep = concat . intersperse sep main :: IO () main = putStrLn . show =<< do -- return $ map (\i -> i * 2) [1, 2, 3] return $ joinList ", " $ map (\x -> [intToDigit x]) [1, 2, 3]