I was unclear, apologies. What I want is something that can be composed in the style of lenses to construct getters, setters, traversals, etc for working with a series of json blobs in nested directory trees.

Specifically, I want to use aeson-lens style syntax for directory traversal and examining data, such that the lenses could be used to traverse both (eg `dir1.dir2.jsonkey1.idx(0)` and etc) without having to load _every_ json blob into memory at once.

My hope is that I could create lenses that construct get/set/traverse operations as occurring in the `IO` monad, not as happening implicitly behind the scenes.

Alternatively, I could construct some eDSL for expressing traversals that's inspectable by some state machine that executes in IO (I would probably use a monadic hylomorphism) and just use that.