varnumbers.pl -- Utilities for numbered terms
This library provides the inverse functionality of the built-in
numbervars/3. Note that this library suffers from the known issues that
'$VAR'(X) is a normal Prolog term and, -unlike the built-in numbervars-,
the inverse predicates do not process cyclic terms. The following
predicate is true for any acyclic term that contains no '$VAR'(X),
integer(X) terms and no constraint variables:
always_true(X) :- copy_term(X, X2), numbervars(X), varnumbers(X, Copy), Copy =@= X2.
- numbervars(+Term) is det
- Number variables in Term using $VAR(N). Equivalent to
numbervars(Term, 0, _).
- varnumbers(+Term, -Copy) is det
- Inverse of numbervars/1. Equivalent to
varnumbers(Term, 0, Copy).
- varnumbers(+Term, +Start, -Copy) is det
- 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.
- max_var_number(+Term, +Start, -Max) is det
- True when Max is the max of Start and the highest numbered $VAR(N) term.
- varnumbers_names(+Term, -Copy, -VariableNames) is det
- If Term is a term with numbered and named variables using the
reserved term '$VAR'(X), Copy is a copy of Term where each
'$VAR'(X) is consistently replaced by a fresh variable and
Bindings is a list
X = Var, relating the X terms with the variable it is mapped to.