anchor.diff:  
   -export([module/1,module/2,form/1,expr/1,expr/2,
            pattern/1,pattern/2,format_error/1]).
  -
  --import(lfe_env, [new/0,is_vbound/2,is_fbound/3,is_gbound/3,
  -                  add_vbinding/3,add_fbinding/4,add_ibinding/5]).
   
   -import(lfe_lib, [is_erl_bif/2,is_guard_bif/2,
                     is_symb_list/1,is_proper_list/1]).
  
positive.code:     %% Add the imports.
      Env0 = foldl(fun ({M,Fs}, Env) ->
                           foldl(fun ({{F,A},R}, E) ->
                                         add_ibinding(M, F, A, R, E)
                                 end, Env, Fs)
                   end, lfe_env:new(), St#lint.imps),
      %% Basic predefines
  
negative.code: %%  Check if Symbol is bound.
  
  check_symb(Symb, Env, L, St) ->
      case lfe_env:is_vbound(Symb, Env) of
          true -> St;
          false -> add_error(L, {unbound_symb,Symb}, St)
      end.
  