Hello Conal,

I have a type

defined in

which is part of the

grapefruit-data package. I introduced it because I wanted to make use of the fact that for every applicative functor a and every monoid m, a m is again a monoid.

defines an instance

(Applicative a, Monoid m) => Monoid (WrappedApplicative a m)

.
Actually,

is just application of a

type to a

type. So it seems much better to define a “composition” type which “composes” a unary type with a nullary type. Such a “composition” would be an instance of

if an applicative functor is composed with a monoid. Thereby I could get rid of

.
Interestingly,

is also type application. Maybe the above ideas could also be used to remove

. Maybe this would lead us to libraries which don’t introduce all kinds of wrapper types.

What do you think?

-- Wolfgang Jeltsch 18:23, 4 December 2007 (UTC)