I'd rather go for LocalTime from the time package, if there must be a custom data type for time and date. But beware: If you parse the line into a Map, then you can not mix the types of the individual fields: all must be the same. Hence in my example I went for String. It is the duty of downstream functions to transform the Map String String into a more detailed data structure. Olaf

Am 19.04.2019 um 16:18 schrieb Jinxuan Zhu :

I feel like the type with Map is not very nice (as map can be anything). Given the simplicity of year parsing , how about traditional

``` data DateTime = DT Int Int Int timeP :: Parser DateTime timeP = DT <*> p <$> p <$> p where p = integer <* char '/' ```

Olaf Klinke writes:

...

You could emulate this with some custom parser combinators on top of any monadic parser combinator library such as attoparsec or megaparsec.

keyed :: (Ord key, Functor parser) => key -> parser a -> parser (Map key a) keyed key = fmap (singleton key)

Then, assuming 'char' and 'digitChar' exists in the parser library, you may write

integer = some digitChar logline = fmap mconcat $ sequence [ keyed "year" (integer <* char '/'), keyed "month" (integer <* char '/'), keyed "day" (integer <* char ' '), -- etc. ]

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