On Fri, Nov 19, 2010 at 15:21, Brent Yorgey
On Fri, Nov 19, 2010 at 07:56:02AM +0100, Tim Baumgartner wrote:
Hi,
while learning about monads, I had something like
do line <- getLine something 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
using 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.
I'm not sure I see any benefit of ': m a -> b -> m b' over 'm a -> m ()'. When would you want to use the former? /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe