[Haskell-cafe] Re: Monads and Functions sequence and sequence_

On 2010-10-30 07:07, Mark Spezzano wrote:

Hi,

Can somebody please explain exactly how the monad functions "sequence" and "sequence_" are meant to work?

I have almost every Haskell textbook, but there's surprisingly little information in them about the two functions.

From what I can gather, "sequence" and "sequence_" behave differently depending on the types of the Monads that they are processing. Is this correct? Some concrete examples would be really helpful.

sequence [m1,m2,m3,m4,...] = do x1 <- m1 x2 <- m2 x3 <- m3 x4 <- m4 ... return [x1,x2,x3,x4,...] sequence_ [m1,m2,m3,m4,...] = do m1 m2 m3 m4 ... return () Cheers,