interface SExpr
	imports Symbol END;

(* @@does ILU have subtyping rules?
	it should be the case that
		SExpr.T <: Refany.T
		if not in ISL, then in the
		implementation languages *)

TYPE T = OPTIONAL Cell;

TYPE Cell = UNION
	pair: Pair,
	symbol: Symbol.T,
	int: INTEGER,
	(* #@float/rat/real? *)
	string: String,
	(* #@intseq, stringseq? *)
	table: Table
	END;
	
TYPE	String = ilu.CString;

TYPE	Pair = 
	       OBJECT BRAND "Pair 1.0" METHODS
		FUNCTIONAL first(): T,
		FUNCTIONAL rest(): T
	End;

(* table allows natural marshalling of:
	perl associative arrays
	scheme hash tables
	python dictionarys
	postscript dictionaries
	SmallTalk dictionaries
*)

TYPE Table = SEQUENCE OF Pair;

(*@@@@@@@@@@2

INTERFACE SExpr;

TYPE Cons = RECORD
     	  car : T,
     	  cdr : T
        END;

TYPE Node = COLLECTABLE OBJECT METHODS
	FUNCTIONAL (*???*) first(): T;
	FUNCTIONAL (*???*) rest(): T;
	END;

TYPE Symbol = ilu.CString; (* hmm... package? some kind of tag? *)

TYPE Cell = UNION
	  node   : Node,
     	  cons   : Cons,
          symbol : Symbol,
          string : ilu.CString,
     	  int    : INTEGER
        END;

TYPE T = OPTIONAL Cell;

*)