Question: Isn't this possible without a full code-port? about copse HOT 5 CLOSED

The problem with newtyping the contained values so that they each hold runtime state required for ordering is that such state must be duplicated across every element in the collection. This has both time and space costs that can be avoided if that state is stored only once per collection.

from copse.

If I understand correctly, could you not then get around large total_orders by storing a Rc<impl TotalOrded> instead and storing the TotalOrder just the once in the BTreeMap Wrapper? Since there is only one impl TotalOrder per BTreeMap?

from copse.

Sure, but that still stores an additional pointer per element and suffers the cost of indirection to reach the ordering (in addition to the cost of the Rc's, or Arc's if multithreaded, alloc + refcounting).

from copse.

Also, your CustomOrdApplicator implementation above assumes that self and other have the same total_order. Perhaps if the library is carefully written, that assumption can be ensured, but to be strictly correct cmp should compare the total_order of the two arguments... and, if they differ, I guess its only option would be to panic? That would add additional cost too.

The outer wrapper type would furthermore have to do translation to/from the stored newtyped keys, which also adds further cost.

from copse.

That makes sense. For sure it would be a sub-optimal solution.

from copse.