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