The Haskell way to do IO Loops (without explicit recursion)?

Question

I want to read a list of strings seperated by newlines from STDIN, until a new line is witnessed and I want an action of the type IO [String]. Here is how I would do it with recursion:

myReadList :: IO String
myReadList = go []
where 
    go :: [String] -> IO [String]   
    go l = do {
                 inp <- getLine;
                 if (inp == "") then 
                     return l;
                 else go (inp:l);
                }

However, this method of using go obscures readability and is a pattern so common that one would ideally want to abstract this out.

So, this was my attempt:

whileM :: (Monad m) => (a -> Bool) -> [m a] -> m [a]
whileM p []     = return []
whileM p (x:xs) = do
    s <- x
    if p s
    then do
        l <- whileM p xs
        return (s:l)
    else
        return []

myReadList :: IO [String]
myReadList = whileM (/= "") (repeat getLine)

I am guessing there is some default implementation of this whileM or something similar already. However I cannot find it.

Could someone point out what is the most natural and elegant way to deal with this problem?

Answer 1

unfoldWhileM is same as your whileM except that it takes an action (not a list) as second argument.

myReadList = unfoldWhileM (/= "") getLine