On Wed, Apr 22, 2015 at 11:38 AM, Shishir Srivastava < shishir.srivastava@gmail.com> wrote:
My next question was how do i only get "34" or "3" i.e. the Maybe value without wrapped in to a 'Maybe' ?
"do" syntax lets you temporarily "unwrap" the value, but it must be rewrapped later. And if the specific monad in question is not IO, you cannot do I/O (e.g. "print" the value as in your initial message). This reflects the mapping of "do" to uses of (>>=) Prelude> :t (>>=) (>>=) :: Monad m => m a -> (a -> m b) -> m b In this example, `m` is Maybe. As it turns out, Maybe is one of the monads that lets you use pattern matching to extract values. Not all monads do; you cannot do this with IO, for example. The `maybe` function is often used instead of explicit pattern matching. -- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net