{TAIL ~ The computer readable storage medium} 10, wherein {HEAD ~ the operation} is parameterized by an element type parameter and a key type parameter 
{ TAIL ~ The computer readable storage medium } 10 , wherein { HEAD ~ the operation } is parameterized by an element type parameter and a key type parameter
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH