11.4.14.1 Term Comparison
- int PL_compare(term_t t1, term_t t2)
 - Compares two terms using the standard order of terms and returns -1, 0 or 1. See also compare/3.
 - int PL_same_compound(term_t t1, term_t t2)
 - Yields 
TRUEif t1 and t2 refer to physically the same compound term andFALSEotherwise.