a comparator to compare {HEAD ~ the search key} to {TAIL ~ the entry} determined to most likely be a match 
to
a comparator to compare { HEAD ~ the search key } to { TAIL ~ the entry } determined to most likely be a match
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH