My apologies my lack of clarity.

The De functor represents a fixed delay, rather than an arbitrary one. I’m dividing time into discrete slices. De x is the type of an x due at the next slice. De (De x) is thus the type of an x due in two slices’ time, and you can’t make it turn up any sooner!

By contrast, Venanzio Capretta’s famed

{-co-}data General x = Now x | Later (General x)

is a monad, with a join that joins up all the delays.

But that ain’t my game here.

Does this make sense?

Cheers

Conor

You write: “Structure cops will note that De is another example of an applicative functor which is not a monad — join would bring things from the far future to the near future, and that had better not be possible. ”

I haven’t made a good effort yet at trying to understand the whole post, but that particular snippet doesn’t sound very convincing to me—somewhat in the same way that an infinity of infinities isn’t that much more of an infinity than a single one.

Is that a wrong way to look at it?