Primitive for updating the upper and lower bounds of Var, also used as the set_bounds handler for the IC attribute. As with lwb/2 and upb/2, it is intended for use in implementing constraint propagators, and should not be called from ordinary user code (use ::/2 instead). Its semantics is essentially:
lwb(Var, Lo), upb(Var, Hi), wake.
Please see the documentation for lwb/2 and upb/2 for more details.