[[!comment format=mdwn username="picca" subject="comment 2" date="2016-02-10T06:41:49Z" content=""" Thanks a lot joey :) I am learning haskell for now and I am not very confortable yet with the haskell Monoid, functor, applicative and monad. So what you are saying is that it would be great to do something like instance monoid Property where mempty = doNothing mappend p1 p2 = combineProperty [p1, p2] mconcat ps = combineProperty ps in order to combine properties. my question is why did you choose to create combineProperty instead of a Monoid at first ? thanks Frederic """]]