SWI-Prolog -- varnumbers/3

Availability::- use_module(library(varnumbers)).(can be autoloaded)

[det]varnumbers(+Term, +Start, -Copy)

Inverse of numbervars/3. True when Copy is a copy of Term with all variables numbered >= Start consistently replaced by fresh variables. Variables in Term are shared with Copy rather than replaced by fresh variables.

Errors: domain_error(acyclic_term, Term) if Term is cyclic.
Compatibility: Quintus, SICStus. Not in YAP version of this library