Build a named list from the LHS of formulas
f_list.Rdf_list makes a new list; as_f_list takes an existing list.
Both take the LHS of any two-sided formulas and evaluate it, replacing the
current name with the result.
f_list.Rdf_list makes a new list; as_f_list takes an existing list.
Both take the LHS of any two-sided formulas and evaluate it, replacing the
current name with the result.