ocaml - ドル + ミリ単位の識別子

Question

私は型チェッカーの$startposと$endposを見ます：.mly

recursive_def:
| f = term_variable
  ty_args = multiple(formal_type_arguments)
  te_args = multiple(term_arguments)
  codomain = preceded(COLON,typ)
  EQ t = loc(term)
    { let loc = ($startpos(ty_args), $endpos(t)) in
      make_recursive_definition f loc ty_args te_args codomain t }
    (* one should check that the right-hand side of a recursive definition
       is a value, e.g. a function or a data constructor application; this
       is not done for the moment. *)

...

pattern:
| d = data_constructor tvars = multiple(formal_type_arguments) LBRACE fields = semi(term_variable) RBRACE
    { SynPatData (($startpos, $endpos), d, tvars, fields) }

...

(* Recording locations. *)

loc(TERM):
| t = TERM
    { SynTeLoc (($startpos, $endpos), t) }

$+の意味を教えてくださいidentifier。それらは関数ですか、それとも変数ですか? それらの値はどのように供給されますか?