I wonder if exists a way to get top n distinct elements from a range (infinite too!)
A (not efficient) way to to this is range.array.sort.uniq.take(n) but it's a bit overkill, it sorts elements, and of course doesn't work with infinite ranges. Am i missing any function?
For an arbitrary infinite range, it is impossible from the mathematical point of view. An impossible example would be doing that with the infinite range of natural numbers, stored in bignums.
For a finite range, you can iterate over the range while maintaining a collection of the top n elements and discarding duplicates as you find them. For example, using a RedBlackTree as the collection, you will get O(log(n) * range.length) total time and O(n) total memory used. If n is small (on the order of 10s), an array will suffice, resulting in O(n * range.length) total time but with lower constant factor.
