getline.hs

module Tets where

getLine' :: IO [Char]
getLine' = getChar >>= \c ->
    if c == '\n' then
      return []
    else
      getLine' >>= \cs ->
      return (c : cs)

getLine'' :: IO [Char]
getLine'' =
  sequenceWhile notNewline $ repeat getChar
  where notNewline c = not (c == '\n')

sequenceWhile :: (a -> Bool) -> [IO a] -> IO [a]
sequenceWhile _ [] = return []
sequenceWhile f (op:ops) =
  op >>= \result ->
  if f result then
    sequenceWhile f ops >>= \results ->
    return (result : results)
  else
    return []

main :: IO ()
main = getLine'' >>= putStrLn

import Control.Monad (when)

-- when is: when p s = if p then s else return ()

getLine' = do
x <- getChar
putChar x
when (x /= '\n') getLine'