Return a functor for comparing two value_type objects by comparing their respective keys using key_comp(). Note that this comparator compares objects of type value_type (i.e., bsl::pair<const KEY, VALUE>).
value_type
key_comp()
bsl::pair<const KEY, VALUE>
Declared in <bslstl_map.h>
<bslstl_map.h>
value_compare value_comp() const;