Monoid instance for CSS

[m-bock]

could there be a monoid instance for CSS?

To me it looks like an empty style is something possible and it would be useful if you pass styles to a function and they should be optional. Because then you'd not have to wrap it in a Maybe.

But - maybe - there are good reasons for not having this.

[Benjmhart]

monoid, and Eq instances would both be very handy.

use case: I have an array of CSS in a state monad, I want to union over them with some new styles, then fold them down into a single rule to be used by a style tag.