anchor.diff:      {Exp,St1} = exp_nequal(Es, Op, St0),
       {yes,Exp,St1};
   exp_predef([Op|Es], _, St0)
  -  when Op == '>'; Op == '>='; Op == '<'; Op == '=<';
  -       Op == '=='; Op == '=:=' ->
  +  when Op =:= '>'; Op =:= '>='; Op =:= '<'; Op =:= '=<';
  +       Op =:= '=='; Op =:= '=:=' ->
       case Es of
           [_|_] ->
               {Exp,St1} = exp_comp(Es, Op, St0),
  
positive.code:     B = foldl(fun ([V,_], Acc) -> exp_bif(Op, [Acc,V]) end, hd(hd(Ls)), tl(Ls)),
      {exp_let_star([Ls,B]),St1}.
  
  %% exp_comp(Args, Op, State) -> {Exp,State}.
  %%  Expand comparison test strictly forcing evaluation of all
  %%  arguments. Note that single argument version may need special
  
negative.code:     Exp = exp_cond(Cbody),
      {yes,Exp,St};
  exp_predef(['do'|Dbody], _, St0) ->
      {Exp,St1} = exp_do(Dbody, St0),
      {yes,Exp,St1};
  exp_predef([lc|Lbody], _, St0) ->
      %% (lc (qual ...) e ...)
  