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copy_term(+OldTerm, ?NewTerm, ?MetaTerms)

A copy of OldTerm with new variables is created and unified with NewTerm. MetaTerms is a list mapping the metaterms in OldTerm to the corresponding variables in NewTerm.
+OldTerm
Prolog term.
?NewTerm
Prolog term, normally a variable.
?MetaTerms
List of Pairs or a variable.

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 a term that is similar to OldTerm but the free variables of OldTerm have been replaced by new variables which do not occur elsewhere.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.

This predicate is a more primitive version of copy_term/2 and does not imply a particular handling of metaterms. Instead it copies the metaterms as normal variables, and returns the MetaTerms list as a means to define the copying of metaterms separately. MetaTerms is a list of pairs [<metaterm>|<variable>] which maps the metaterms in OldTerm to the corresponding fresh variables in NewTerm. By processing this list, the variables can be instantiated to whatever the user defines as the copy of the metaterm.

Note that copy_term/2 is implemented as 

    copy_term(X, Y) :-
        copy_term(X, Y, Metas),
        apply_copy_term_handlers(Metas).

Fail Conditions

Fails if NewTerm does not unify with the copy of OldTerm.

Resatisfiable

No.

Examples

[eclipse 1]: set_flag(output_mode, "QPMV").

yes.
[eclipse 3]: copy_term(s(a,X{a},Y, Z{b}), Copy, Metas).

X = X_m234{a}
Y = Y_g224
Z = Z_m212{b}
Copy = s(a, _g282, Y_g288, _g292)
Metas = [[Z_m212{b}|_g292], [X_m234{a}|_g282]]
yes.

See Also

copy_term / 2, copy_term_vars / 3, variant / 2, term_variables / 2