PtmapSourceMaps over integers implemented as Patricia trees.
The following signature is a subset of Map.S with type key = int, with the same specifications (not repeated here) unless specified otherwise.
These are little-endian Patricia trees, so there is no efficient ordering of keys within the structure. Consequently,
min/max_binding, find_first/last are rather inefficient (linear)iter, fold *do not* iterate in the key orderbindings is *not sorted* by keys