Re: [Haskell-beginners] how to skip pattern match error when applying a mapM_

I don't know if 'row' contains any side effects that should also be executed if the returned 'Maybe' is 'Nothing', if this isn't the case, then you might be able to switch the return type of 'row' from 'IO (Maybe ...)' to 'Maybe (IO ...)' and then you could get the described behaviour for 'Maybe'.

As soon as one side effect return Nothing, it should stop the IO monad. so I should definitiely switch to Maybe IO now how can I know the behaviour in between the line of a Monad. I aimagine that this is the purpose of the bind method (>>=). Where is this defined for Maybe and IO ? Thanks Frederic