[volta83]

> You need some way to enforce that the orderings are the _same_

Just require that the Ord type is the same for all heaps ?

MaxHeap(MaxHeap(T, MyOrd), MyOrd) uses the same ordering, but MaxHeap(MaxHeap(T, Ord0), Ord1) does not.

[volta83]

A simple way to do this is to:

MyNestedMaxHeap(T, Ord) = MaxHeap(MaxHeap(T, Ord), Ord)

such that when using MyNestedMaxHeap only one Ord type can be passed.