Nonzero magnitude: Prisms and lenses

More on affine traversals (how to define them)

The first part of this series argues that affine traversals should be considered the core optics concept. You might ask, if that's true, why does everybody talk about “prisms” and “lenses” so much?

The centrality of AffineTraversal

Part two gave an example of a class of affine traversals, but I did not give instances to define them.

Positive integers and affine traversal

Here I pick up where that left off, and in the process I…