•Unlike a hashed map, there’s no need for ordered map "=" to search for the key, since the keys are
already in sort order.
•If the key in the left map is equivalent to
the corresponding key in the
right map (equivalence being defined
in terms of key "<"), then ordered map "=" compares the associated elements for equality. (This is the only time when element "=" is actually
used.)
•Note that the key and element are both used to compute ordered map equality, but key equality is not used. (In fact key
equality is never used in this API.)