Re: [Haskell-cafe] instance Monoid a => Monad ((,) a)

5 Aug 2019

      On 2019-08-05 2:33 p.m., Jinxuan Zhu wrote:

    … Bool can be monoid by either || or && operations, which would lead
    to ambiguity if Bool is monoid by default.

    You can:

     1. use Maybe Unit instead
     2. (overkill) Define AndMonoid Bool newtype and use DeriveVia and
        coerce

|Data.Monoid| from |base| already has |Any| and |All| for this.

Re: [Haskell-cafe] instance Monoid a => Monad ((,) a)

Neil Mayhew