anchor.diff:  eval(Sexpr) -> eval(Sexpr, lfe_env:new()).  %Empty environment.
   eval(Sexpr, Env) -> lfe_eval:expr(Sexpr, Env).
   
  +'macro-function'(Symb) -> 'macro-function'(Symb, lfe_env:new()).
  +'macro-function'(Symb, Env) ->
  +    case lfe_env:get_mbinding(Symb, Env) of
  +        {yes,Macro} ->
  +            Macro;
  +        no -> []
  +    end.
  +
   macroexpand(Form) -> macroexpand(Form, lfe_env:new()).
   macroexpand(Form, Env) ->
       case lfe_macro:expand_expr(Form, Env) of
  -    {yes,Exp} -> Exp;
  -    no -> Form
  +        {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
  +        {yes,Exp} -> Exp;
  +        no -> Form
       end.
   
   'macroexpand-all'(Form) -> 'macroexpand-all'(Form, lfe_env:new()).
  
positive.code: is_lfe_bif(sublis, 2) -> true;
  is_lfe_bif(eval, 1) -> true;
  is_lfe_bif(eval, 2) -> true;
  is_lfe_bif(macroexpand, 1) -> true;
  is_lfe_bif(macroexpand, 2) -> true;
  is_lfe_bif('macroexpand-1', 1) -> true;
  
negative.code: %% subst-if-not(New, Test, Tree) -> Tree.
  %% sublis(Alist, Tree) -> Tree.
  %% eval(Sexpr) -> Value.
  %% macro-function(Name [,Environment]) -> Macro | [].
  %% macroexpand(Form [,Environment]) -> Expansion | Form.
  %% macroexpand-1(Form [,Environment]) -> Expansion | Form.
  %% macroexpand-all(Form [,Environment]) -> Expansion | Form.
  
  is_lfe_bif(acons, 3) -> true;
  is_lfe_bif(pairlis, 2) -> true;
  