On 15/08/12 17:01, José Lopes wrote:

someFn docs = return concat `ap` (sequence $ intersperse (return "\n") (map loop docs))

First of all, "return x `ap` y" = "x `fmap` y" or "x <$> y". fmap (or its infix synonym (<$>)) is the answer here, you could write: someFn docs = concat . intersperse "\n" <$> mapM loop docs The function Data.List.intercalate is a compation of concat and intersperse, so you could write: someFn docs = intercalate "\n" <$> mapM loop docs or, depending on your preference, someFn = fmap (intercalate "\n") . mapM loop Twan

Try: concat . intersperse "\n" <$> (sequence $ map loop docs) On Wed, Aug 15, 2012 at 11:01 AM, José Lopes wrote:

Hello everyone,

I am quite new to monadic code so I would like to ask for improvement suggestions on the last line of the code below. I know I could do something like "do strs <- mapM ...; intercalate ..." etc, but I would like to avoid the use of "<-".

Thank you, José

data XmlState = XmlState Int type XmlM a = State XmlState a

loop :: Document -> XmlM String

someFn :: [Document] -> XmlM String someFn docs = return concat `ap` (sequence $ intersperse (return "\n") (map loop docs)) <--- improve this line

-- José António Branquinho de Oliveira Lopes 58612 - MEIC-A Instituto Superior Técnico (IST), Universidade Técnica de Lisboa (UTL) jose.lopes@ist.utl.pt

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