Can we improve fromList?

[treeowl]

O(n log n) is pretty wretched. One simple option is to use fromListN with length. It's kind of nasty though, and may or may not be faster in practice.

[treeowl]

I think I have a sensible approach to this. Using mutable array primitives, fill successively larger arrays with elements (O(n)), keeping track of the count. Once the elements are exhausted, build the stack/queue. Note that unlike anything else in the package, we almost certainly want to use "large" arrays rather than small ones if we do this, since mutation may be interleaved with computation.