Availability:built-in
[det]variant_hash(+Term, 
-HashKey)Similar to variant_sha1/2, 
but using a non-cryptographic hash and produces an integer result like term_hash/2. 
This version does deal with attributed variables, processing them as 
normal variables. This hash is primarily intended to speedup finding 
variant terms in a set of terms.
bugAs variant_sha1/2, 
cyclic terms result in an exception.