MonadAccum

[kozross]

This defines a type class, along with a helper DerivingVia type, a bunch of instances, documentation and laws, to address the corresponding entry in #86.

This is WIP for now, as I want to add some details about the meaning of the various instances, which may not be 100% obvious to a first-time reader.

[emilypi]

WIP, needs some expanded docs, but otherwise LGTM

[emilypi]

I actually kind of like this doc style. 👍

[kozross]

Can't claim any credit here. I'm just using what already existed for (at least) MonadCont.

[emilypi]

I would name these laws:

1. [Pure-Quot] (in the sense of pure x being quotiented with (x, mempty))
2. [Const-Accum] because it is what it says it is.

[kozross]

We'd need to name all the others too, then. Good idea though.

[turion]

I guess you're aware of #89, on which I took a break because I didn't quite get how the docs were supposed to be structured.

[turion]

And, I should add, I can finish #89 if that saves you work & brain capacity.

[kozross]

@turion At this point I'm nearly done anyway - I just have some docs to add and that's it. But thanks for offering!

[emilypi]

@kozross we should add @turion as a coauthor on the squash/rebased commit to master just to acknowledge their additions. We (chessai and myself) let their PR languish, and that's why it didn't go in.

[kozross]

@emilypi My work is clean-room, though I'm happy to add @turion into the list of authors.

[kozross]

@emilypi and @chessai - I wrote the docs I wanted, and addressed all the things needing addressing. I couldn't do a proper description of what the SelectT stack does, but that's because I don't even know what SelectT does in general, as @emilypi is aware.