[Haskell-beginners] Ignoring the result of a monadic computation
byorgey at seas.upenn.edu
Fri Nov 19 10:21:10 EST 2010
On Fri, Nov 19, 2010 at 07:56:02AM +0100, Tim Baumgartner wrote:
> while learning about monads, I had something like
> line <- getLine
> putStrLn line
> and I wondered if I could write it in one line, without naming of parameters.
> I finally came up with
> getLine >>= ignore something >>= putStrLn
> ignore :: Monad m => m a -> b -> m b
> ignore m a = m >> return a
> I'm satisfied with this solution but searching hoogle I didn't find
> a standard function for my ignore. Am I missing something?
Nope, there isn't such a function, but I like it. It reminds me of
(*>) and (<*) from Control.Applicative. Note that you sometimes see
the name 'ignore' used for a slightly different function, namely
ignore :: Monad m => m a -> m ()
ignore m = m >> return ()
but yours is a bit more general. Other names for your function might
be 'passThrough' or something like that.
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