Availability:built-in
numbervars(+Term,
+Start, -End, +Options)As numbervars/3,
providing the following options:
- functor_name(+Atom)
- Name of the functor to use instead of
$VAR.
- attvar(+Action)
- What to do if an attributed variable is encountered. Options are
skip, which causes numbervars/3
to ignore the attributed variable, bind which causes it to
treat it as a normal variable and assign the next '$VAR'(N)
term to it, or (default)
error which raises a type_error exception.117This
behaviour was decided after a long discussion between David Reitter,
Richard O'Keefe, Bart Demoen and Tom Schrijvers.
- singletons(+Bool)
- If
true (default false), numbervars/4
does singleton detection. Singleton variables are unified with '$VAR'('_'),
causing them to be printed as _ by write_term/2
using the numbervars option. This option is exploited by portray_clause/2
and write_canonical/2.bugCurrently
this option is ignored for cyclic terms.