The `sequence`, `mapM`, and `mapM_` functions may be what you are looking for.
let allTogether = sequence [doA, doB, doC, doZ]
case allTogether of
Nothing -> ...
Just as -> ...
Use `maybe` and `fromMaybe` to avoid case statements:
fromMaybe "failure!" $ do
as <- sequence [doA, doB, doC, doZ]
return $ "Success: " ++ show (length as)
The `catMaybes` function can be used to execute each computation in
the list even if some of them return nothing.
On Fri, Sep 6, 2013 at 12:49 PM, Emmanuel Touzery
Hello,
I'm often using the Maybe monad to combine Maybe computations one after the other without conditionals.
But I'm not sure how to do it, when I have several operations which return Maybe and I want all the indiviual values in the end, not a combination of the values.
Currently I do:
let allTogether = do ma <- doA mb <- doB return (ma, mb) case allTogether of Nothing -> ... Just (a, b) -> ...
This way in this case I have one case instead of two, however I'm sure there must be a nicer way to achieve this result?
Thank you!
Emmanuel
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