Availability:built-in
[det]term_hash(+Term, 
+Depth, +Range, -HashKey)As term_hash/2, 
but only considers Term to the specified
Depth. The top-level term has depth 1, its arguments have 
depth 2, etc. That is, Depth = 0 hashes nothing; Depth 
= 1 hashes atomic values or the functor and arity of a compound 
term, not its arguments; Depth = 2 also indexes 
the immediate arguments, etc.
HashKey is in the range [0 ...Range-1]. Range 
must be in the range [1 ... 2147483647].