
copy_term(?OldTerm, -NewTerm)

   A copy of OldTerm with new variables is created and unified with NewTerm.



Arguments
   OldTerm             Prolog term.
   NewTerm             Prolog term.

Type
   Term Manipulation

Description
   A copy of OldTerm is created, ie.  a term that is similar to OldTerm but
   the free variables of OldTerm have been replaced by new variables which
   do not occur elsewhere.  In other words, the new term is a most general
   variant of the old one in the sense of variant/2.


   Metaterms are treated like normal variables, except that their
   attributes are copied as specified by the corresponding copy_term handler.


   The effect of copy_term/2 is almost the same as of the sequence



    setval(reserved_name, OldTerm),
    getval(reserved_name, NewTerm)

   or a similar application of record/erase or assert/retract.  However,
   copy_term/2 is faster, handles attributed variables more sensibly and is also
   more space efficient since it does not physically copy ground subterms.


   Note that when the structure of the term to be copied is known, then
   it is more efficient to use specialised unification code or a combination
   of functor/3 and arg/3 to do the job.




Modes and Determinism
   copy_term(?, -) is det

Examples
   
   Success:
   copy_term(a, C).          (gives C=a).
   copy_term(s(X,a,Y,X), C). (gives C=s(_g1, a, _g2, _g1)).
   copy_term([X,2|Y], C).    (gives C=[_g1, 2| _g2]).
   copy_term(X, C).
   copy_term(X, s(1,2,3)).
   Fail:
   copy_term(s(X,X), s(3,4)).





See Also
   copy_term_vars / 3, copy_term / 3, variant / 2, functor / 3, term_variables / 2
