anchor.diff:  is_lfe_bif(sublis, 2) -> true;
   is_lfe_bif(eval, 1) -> true;
   is_lfe_bif(eval, 2) -> true;
  +is_lfe_bif('macro-function', 1) -> true;
  +is_lfe_bif('macro-function', 2) -> true;
   is_lfe_bif(macroexpand, 1) -> true;
   is_lfe_bif(macroexpand, 2) -> true;
   is_lfe_bif('macroexpand-1', 1) -> true;
  
positive.code: eval(Sexpr) -> eval(Sexpr, lfe_env:new()).  %Empty environment.
  eval(Sexpr, Env) -> lfe_eval:expr(Sexpr, Env).
  
  macroexpand(Form) -> macroexpand(Form, lfe_env:new()).
  macroexpand(Form, Env) ->
      case lfe_macro:expand_expr(Form, Env) of
      {yes,Exp} -> Exp;
      no -> Form
      end.
  
  'macroexpand-1'(Form) -> 'macroexpand-1'(Form, lfe_env:new()).
  'macroexpand-1'(Form, Env) ->
      case lfe_macro:expand_expr_1(Form, Env) of
      {yes,Exp} -> Exp;
      no -> Form
      end.
  
  'macroexpand-all'(Form) -> 'macroexpand-all'(Form, lfe_env:new()).
  
negative.code: 
  %% Standard lisp library.
  -export([is_lfe_bif/2,
           acons/3,pairlis/2,pairlis/3,
           assoc/2,'assoc-if'/2,'assoc-if-not'/2,
           rassoc/2,'rassoc-if'/2,'rassoc-if-not'/2,
           subst/3,'subst-if'/3,'subst-if-not'/3,sublis/2,
           eval/1,eval/2,
           'macro-function'/1,'macro-function'/2,
           macroexpand/1,macroexpand/2,
           'macroexpand-1'/1,'macroexpand-1'/2,
           'macroexpand-all'/1,'macroexpand-all'/2]).
  
  %% Miscellaneous useful LFE functions.
  -export([format_exception/6,format_stacktrace/3]).
  