Hi David, David Thomas wrote:

https://github.com/dlthomas/tzcache A small bit of code, but seems likely to be useful enough that I figured I should share.

Thanks for sharing this!

1) Does this already exist somewhere I missed?

I haven't seen it anywhere.

2) It seems silly to make this its own library

- any suggestions where it could be added?

If you feel it is appropriate, I would be willing to add it to timezone-olson. Does anyone else have an opinion about it? 3) Is the traverse-a-directory-and-populate-a-map pattern one worth abstracting? If so, where should that go?

I think the proper abstraction would be a more general fold or traversal over a directory structure. Some languages have something like that (e.g., os.walk in Python). But look how simply it worked out for you in Haskell - perhaps that's why there doesn't seem to be a standard function for this anywhere. That said, it might be interesting to have this as a lens-package-style traversal. 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.

Yes. The total amount of timezone data in the world is likely to continue increasing at a significantly slower rate than Moore's law. 5) Any comments on the code generally? Improvements? Complaints?

I like your code. I'm not sure how well this brute-force mapM recursion would scale over a timezone directory structure with, say, millions of nodes. But that's not the use case here at all. Thanks, Yitz