The built-in predicates described in this section allows the user to compare
Prolog terms. Prolog terms are totally ordered according to the standard
total ordering of terms which is as follows (from the smallest term to the
greatest):
atoms, in alphabetical (i.e. character code) order.
compound terms, ordered first by arity, then by the name of the
principal functor and by the arguments in left-to-right order.
A list is treated as a compound term (whose principal functor is
'.'/2).
The portability of the order of variables is not guaranteed (in the ISO
reference the oder of variables is system dependent).
6.3.2
(==)/2 - term identical,
(\==)/2 - term not identical, (@<)/2 - term less than,
(@=<)/2 - term less than or equal to, (@>)/2 - term greater than,
(@>=)/2 - term greater than or equal to