anchor.diff:      no ->
           case find(S, Bbs) of
           {ok,V} -> V;
  -        error -> erlang:error({unbound_symb,S})
  +        error -> eval_error({unbound_symb,S})
           end
       end.
   
  
positive.code: match_symb(S, Val, Pbs, _) ->
      %% Check if Symb already bound.
      case find(S, Pbs) of
          {ok,_} -> erlang:error({multi_var,S});  %Already bound, multiple var
          error -> {yes,store(S, Val, Pbs)}       %Not yet bound
      end.
  
  
negative.code:         no -> no
      end;
  %% match([_|_], _, _, _) ->                        %No constructor
  %%     eval_error(illegal_pattern);
  match([], [], Pbs, _) -> {yes,Pbs};
  match(Symb, Val, Pbs, Env) when is_atom(Symb) ->
      match_symb(Symb, Val, Pbs, Env);
  