Thanks. That looks like the right thing. It's kind of a strange name for it though, without the context. Basically, Semi m = Constant . Constant m I wonder if something similar by a different name might fit in transformers. On Mon, Jun 22, 2015 at 1:13 PM, Patrick Chilton wrote:

Looks like Semi from semigroupoids: https://hackage.haskell.org/package/semigroupoids-5.0.0.2/docs/Data-Semigrou...

On Mon, Jun 22, 2015 at 5:51 PM, David Feuer wrote:

...

Is there a newtype defined in some normal sort of place for turning Monoids into Categories? I'm looking for something like this:

newtype ConstConst m a b = ConstConst m

instance Monoid m => Category (ConstConst m) where id = ConstConst mempty ConstConst x . ConstConst y = ConstConst (x <> y)

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