Re: [Haskell-cafe] Could someone teach me why we use Data.Monoid?

Magnus Therning wrote:

On Fri, Nov 13, 2009 at 4:52 PM, Andrew Coppin wrote:

...

A class that represents "any possible thing that can technically be considered a monoid" seems so absurdly general as to be almost useless. If you don't know what an operator *does*, being able to abstract over it isn't especially helpful...

But can't you say exactly the same about Monads?

I know nothing about how mathematicians use monads. However, Haskell uses them in one specific way: for controlling (not necessarily _sequencing_) statement execution. This is a fairly rigidly-defined notion. By contrast, Integer forms an infinite family of different monoids, yet it can have only a single Monoid instance... I notice that there's a an Alternative class, which is isomorphic to Monoid, but rather than being some arbitrary monoid, it's a monoid with a specific meaning. This, I would argue, is far more useful.