Term comparison and manipulation

• Term1 == Term2: The terms Term1 and Term2 are strictly identical.

• Term1 \== Term2: The terms Term1 and Term2 are not strictly identical.

• Term1 @< Term2: The term Term1 precedes the term Term2 in the standard order.

• Term1 @=< Term2: The term Term1 either precedes, or is identical to, the term Term2 in the standard order.

• Term1 @> Term2: The term Term1 follows the term Term2 in the standard order.

• Term1 @>= Term2: The term Term1 either follows, or is identical to, the term Term2 in the standard order.

• compare(Op,Term1,Term2): Op is the result of comparing the terms Term1 and Term2.

• copy_term(Term,CopyOfTerm): CopyOfTerm is an independent copy of Term. For an attributed variable, the copy does not carry any of the attributes.

• acyclic_term(Term): This fails if Term is cyclic, and succeeds otherwise.

• number_vars(Term,N0,N):
• numbervars(Term,N0,N): Number the variables in Term by using the integers starting from N0. N is the next integer that is available after the term is numbered. Let N0, N1, ..., N-1 be the sequence of integers. The first variable is bound to the term $var(N0), the second variable is bound to $var(N1), and so on. Different variables receive different numberings. All occurrences of the same variable receive the same numbering. (not in ISO).

• unnumber_vars(Term1,Term2): Term2 is a copy of Term1, with all numbered variables $var(N) being replaced by Prolog variables. Different numbered variables are replaced by different Prolog variables.

  Number the variables in Term by using the integers starting from N0. N is the next integer that is available after the term is numbered. Let N0, N1, ..., N-1 be the sequence of integers. The first variable is bound to the term $var(N0), the second variable is bound to $var(N1), and so on. Different variables receive different numberings. All occurrences of the same variable all receive the same numbering. (not in ISO).

• term_variables(Term,Vars):
• vars_set(Term,Vars): Vars is a list of variables that occur in Term.

• term_variables(Term,Vars,Tail): This is the difference list version of term_variables/2. Tail is the tail of the incomplete list Vars.

• variant(Term1,Term2): This is true if Term1 is a variant of Term2. No attributed variables can occur in Term1 or in Term2.

• subsumes_term(Term1,Term2): This is true if Term1 subsumes Term2. No attributed variables can occur in Term1 or in Term2.

• acyclic_term(Term): This succeeds if Term is acyclic, and fails otherwise.