anchor.diff:  
   exp_macro([Name|_]=Call, Env, St) ->
       case lfe_lib:is_core_form(Name) of
  -    true -> no;                %Never expand core forms
  -    false ->
  -        case get_mbinding(Name, Env) of
  -        {yes,Def} ->
  -            %% User macro bindings.
  -            exp_userdef_macro(Call, Def, Env, St);
  -        no ->
  -            %% Default macro bindings.
  -            exp_predef_macro(Call, Env, St)
  -        end
  +        true -> no;                             %Never expand core forms
  +        false ->
  +            case get_mbinding(Name, Env) of
  +                {yes,Def} ->
  +                    %% User macro bindings.
  +                    exp_userdef_macro(Call, Def, Env, St);
  +                no ->
  +                    %% Default macro bindings.
  +                    exp_predef_macro(Call, Env, St)
  +            end
       end.
   
   %% exp_userdef_macro(Call, Def, Env, State) -> {yes,Exp,State}.
  
positive.code: -export([format_error/1]).
  
  -export([mbe_syntax_rules_proc/4,mbe_syntax_rules_proc/5,
       mbe_match_pat/3,mbe_get_bindings/3,mbe_expand_pattern/3]).
  
  %% -compile([export_all]).
  
  -import(lfe_env, [new/0,add_fbinding/4,is_fbound/3,
            add_mbinding/3,is_mbound/2,get_mbinding/2]).
  
  -import(lfe_lib, [is_symb_list/1,is_proper_list/1]).
  
  -import(lists, [any/2,all/2,map/2,foldl/3,foldr/3,mapfoldl/3,
          reverse/1,reverse/2,member/2,concat/1]).
  -import(orddict, [find/2,store/3]).
  -import(ordsets, [add_element/2,is_element/2]).
  
  -include("lfe_comp.hrl").
  -include("lfe_macro.hrl").
  
  %% Errors
  format_error({bad_form,Type}) ->
  
negative.code:     %%lfe_io:format("udef: ~p\n", [[Mac|Args]]),
      %%lfe_io:format("macro: ~p\n", [Def0]),
      try
          {Def1,St1} = exp_form(Def0, Env, St0),  %Expand definition
          Exp = lfe_eval:apply(Def1, [Args,Env], Env),
          {yes,Exp,St1}
      catch
          error:Error ->
              Stack = erlang:get_stacktrace(),
              erlang:error({expand_macro,[Mac|Args],{Error,Stack}})
      end.
  
  %% exp_predef_macro(Call, Env, State) -> {yes,Exp,State} | no.
  