1.1 --- a/src/Pure/Isar/outer_parse.ML	Tue Oct 26 00:04:05 1999 +0200
     1.2 +++ b/src/Pure/Isar/outer_parse.ML	Tue Oct 26 14:34:50 1999 +0200
     1.3 @@ -26,6 +26,7 @@
     1.4    val sync: token list -> string * token list
     1.5    val eof: token list -> string * token list
     1.6    val not_eof: token list -> token * token list
     1.7 +  val opt_unit: token list -> unit * token list
     1.8    val nat: token list -> int * token list
     1.9    val enum: string -> (token list -> 'a * token list) -> token list -> 'a list * token list
    1.10    val enum1: string -> (token list -> 'a * token list) -> token list -> 'a list * token list
    1.11 @@ -136,6 +137,8 @@
    1.12  
    1.13  val not_eof = Scan.one OuterLex.not_eof;
    1.14  
    1.15 +val opt_unit = Scan.optional ($$$ "(" -- $$$ ")" >> (K ())) ();
    1.16 +
    1.17  
    1.18  (* enumerations *)
    1.19