[Haskell-cafe] Newbie : What does the sequence function make?
Benjamin Franksen
benjamin.franksen at bessy.de
Mon May 2 14:45:39 EDT 2005
On Monday 02 May 2005 19:42, mandziy at web.de wrote:
> Please,can anyone explain it to me?
From
http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control.Monad.html
sequence :: Monad m => [m a] -> m [a]
Evaluate each action in the sequence from left to right, and collect the
results.
Another way to explain what sequence does is the following implementation,
which I find a bit easier to understand for the beginner than the one given
in http://www.haskell.org/onlinelibrary/standard-prelude.html :
sequence [] = []
sequence m:ms = do
x <- m
xs <- sequence ms
return (x:xs)
HTH,
Ben
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