Sorry for not getting back to you sooner on this. Indexing into an extrapolation object like that should work - if you haven't already solved that problem, could you please file an issue with a complete (runnable) code sample?
Regarding the comprehension, did you do that in the repl or in a script? Does it still yield Any[] if you wrap it in a function? If so, it might indicate a type stability issue in extrapolate - please file an issue for that too then. Thanks! // T
