anchor.diff:  -type c_let()     :: #c_let{}.
   -type c_letrec()  :: #c_letrec{}.
   -type c_literal() :: #c_literal{}.
  +-type c_map()     :: #c_map{}.
  +-type c_map_pair_assoc()  :: #c_map_pair_assoc{}.
  +-type c_map_pair_exact()  :: #c_map_pair_exact{}.
   -type c_module()  :: #c_module{}.
   -type c_primop()  :: #c_primop{}.
   -type c_receive() :: #c_receive{}.
  
positive.code: 
  %% ---------------------------------------------------------------------
  %% maps
  
  map_es(#c_map{es = Es}) ->
      Es.
  
negative.code: -type c_var()     :: #c_var{}.
  
  -type cerl() :: c_alias()  | c_apply()  | c_binary()  | c_bitstr()
                | c_call()   | c_case()   | c_catch()   | c_clause()  | c_cons()
                | c_fun()    | c_let()    | c_letrec()  | c_literal()
  	      | c_map()    | c_map_pair_assoc()       | c_map_pair_exact()
  	      | c_module() | c_primop() | c_receive() | c_seq()
                | c_try()    | c_tuple()  | c_values()  | c_var().
  
  %% =====================================================================
  