[Haskell-cafe] Recursive timezone-loading function

https://github.com/dlthomas/tzcache A small bit of code, but seems likely to be useful enough that I figured I should share. I've a few notes/questions: 1) Does this already exist somewhere I missed? 2) It seems silly to make this its own library - any suggestions where it could be added? 3) Is the traverse-a-directory-and-populate-a-map pattern one worth abstracting? If so, where should that go? 4) Presently, it's a static cache entirely pre-loaded. This seems fine, as it's not a terribly huge amount of data, but it's worth noting. 5) Any comments on the code generally? Improvements? Complaints? Thanks, - David