More overlap with Control.Lens

[bergey]

A few more overlaps, not mentioned in #82:

at
view
over

I don't know how important these are to either library. For Metafont work, I hid at from Lens and view, over from Diagrams. It's likely that if I knew what the other 3 functions did, I'd use them.

[byorgey]

• at: for creating Located things in diagrams, and accessing indexed containers (e.g. arrays, maps) in lens. Both can be important, it depends on your use case.
• view: for setting a new Envelope in diagrams (probably not very common), and for turning a lens into a function (with (^.) as a synonym).
• over: in diagrams, re-exported from colour, for compositing two colors with transparency. In lens, for editing the contents of a setter (with (%~) as a synonym).

Of these I'd be fine with removing our re-export of over; most users will not need it, and those who explicitly want to do some fancy color computations can import Data.Colour.

Two libraries as huge as diagrams and lens are almost guaranteed to have some name clashes. I'd rather not waste time rearranging the furniture; if we run into clashes that are particularly common or annoying we can consider them on a case-by-case basis.

[bergey]

if we run into clashes that are particularly common or annoying we can consider them on a case-by-case basis.

Makes sense. I ran into these working on the MetaFont module, and hiding whichever I wasn't using wasn't annoying.