//PureLisp
import gi.*;

class PureLisp extends SLR1_Grammar {
//PureLisp.Pair
/*\semantics*/	class Pair {

		Object car;
		Object cdr;

		Pair(Object car, Object cdr) {
			this.car = car;
			this.cdr = cdr;
		}

		public String toString() {
			return format(this);
		}
//PureLisp.Pair
	}/*\off*/
//PureLisp.cons
/*\semantics*/	Object cons(Object e1, Object e2) {
		return new Pair(e1, e2);
	}

	Object car(Object e) throws Exception {
		if (!(e instanceof Pair)) throw new Exception(
			"car operation undefined");

		return ((Pair)e).car;
	}

	Object cdr(Object e) throws Exception {
		if (!(e instanceof Pair)) throw new Exception(
			"cdr operation undefined");

		return ((Pair)e).cdr;
	}

	Object cadr(Object e) throws Exception {return car(cdr(e));}
	Object caddr(Object e) throws Exception {return car(cdr(cdr(e)));}
	Object caar(Object e) throws Exception {return car(car(e));}
	Object cadar(Object e) throws Exception {return car(cdr(car(e)));}
	Object caddar(Object e) throws Exception {return car(cdr(cdr(car(e))));}/*\off*/
//PureLisp.eq
/*\semantics*/	boolean eq(Object e1, Object e2) throws Exception {
		if (e1 == null && e2 == null)
			return true;
		else if (e1 instanceof String && e2 instanceof String)
			return e1.equals(e2);
		else if (e1 instanceof Pair && e2 instanceof Pair)
			return eq(car(e1), car(e2)) && eq(cdr(e1), cdr(e2));
		else
			return false;
	}/*\off*/
//PureLisp.condval
/*\semantics*/	Object condval(Object cases, Object env) throws Exception {
		if (cases == null) throw new Exception(
			"cond operation undefined");

		if (eval(caar(cases), env) != null)
			return eval(cadar(cases), env);
		else
			return condval(cdr(cases), env);
	}/*\off*/
//PureLisp.atomval
/*\semantics*/	Object atomval(Object identifier, Object env) throws Exception {
		if (env == null) throw new Exception(
			identifier + " undefined");

		if (eq(identifier, caar(env)))
			return cdr(car(env));
		else
			return atomval(identifier, cdr(env));
	}/*\off*/
//PureLisp.bind
/*\semantics*/	Object bind(Object formals, Object exprs, Object env) throws Exception {
		if (formals == null && exprs == null)
			return env;
		else
			return cons(cons(car(formals), eval(car(exprs), env)),
					bind(cdr(formals), cdr(exprs), env));
	}/*\off*/
//PureLisp.eval
/*\semantics*/	Object eval(Object e, Object env) throws Exception {
		if (e == null)
			return e;
		else if (e instanceof String)
			return (e.equals("T")) ? e : atomval(e, env);
		else if (car(e) instanceof String)
			if (car(e).equals("quote"))
				return cadr(e);
			else if (car(e).equals("car"))
				return car(eval(cadr(e), env));
			else if (car(e).equals("cdr"))
				return cdr(eval(cadr(e), env));
			else if (car(e).equals("cons"))
				return cons(eval(cadr(e), env), eval(caddr(e), env));
			else if (car(e).equals("atom"))
				return (eval(cadr(e), env) instanceof String) ? "T" : null;
			else if (car(e).equals("eq"))
				return (eq(eval(cadr(e), env), eval(caddr(e), env))) ? "T" : null;
			else if (car(e).equals("cond"))
				return condval(cdr(e), env);
			else
				return eval(cons(atomval(car(e), env), cdr(e)), env);
		else if (caar(e) instanceof String)
			if (caar(e).equals("lambda"))
				return eval(caddar(e), bind(cadar(e), cdr(e), env));
			else if (caar(e).equals("label"))
				return eval(cons(caddar(e), cdr(e)),
						cons(cons(cadar(e), caddar(e)), env));
			else
				throw new Exception(
					"eval operation undefined");
		else
			throw new Exception(
				"eval operation undefined");
	}/*\off*/

	String formatCdr(Object e) {
		if (e == null)
			return "";
		else if (e instanceof String)
			return "." + e;
		else
			return " " + format(((Pair)e).car) + formatCdr(((Pair)e).cdr);
	}

	String format(Object e) {
		if (e == null)
			return "NIL";
		else if (e instanceof String)
			return (String)e;
		else
			return "(" + format(((Pair)e).car) + formatCdr(((Pair)e).cdr) + ")";
	}
//PureLisp

	PureLisp() throws Exception {
		put("IDENTIFIER", expression("[[:alnum:]]+"));
		put("SPACE", expression("[[:space:]]+"));
		put("T", expression("T|t"));
		put("NIL", expression("NIL|nil"));

		// /*\semantics*/semantic specification/*\off*/
//PureLisp.Program
/*\semantics*/		Semantics interpret = new Semantics() {
			public void f(ParseTree t, int l) throws Exception {
				t.value = eval(t.child[l-1].value, null);
				System.out.println(format(t.value));
			}
		};
/*\off*/		put("Program", new Object[][] {
			{"Expr"/*\semantics*/, interpret/*\off*/}
		});
//PureLisp.Expr
/*\semantics*/		Semantics identity = new Semantics() {
			public void f(ParseTree t, int l) {
				t.value = t.child[l-1].value;
			}
		};
/*\off*/		put("Expr", new Object[][] {
			{"Atom"/*\semantics*/, identity/*\off*/},
			{"List"/*\semantics*/, identity/*\off*/},
		});
//PureLisp.Atom
/*\semantics*/		Semantics truth = new Semantics() {
			public void f(ParseTree t, int l) {
				t.value = "T";
			}
		};
/*\off*/		put("Atom", new Object[][] {
			{"T"/*\semantics*/, truth/*\off*/},
			{"IDENTIFIER"/*\semantics*/, identity/*\off*/},
		});
//PureLisp.List.NIL
/*\semantics*/		Semantics list_zero = new Semantics() {
			public void f(ParseTree t, int l) {
				t.value = null;
			}
		};
/*\off*/		put("List", new Object[][] {
			{"NIL"/*\semantics*/, list_zero/*\off*/}
		});
//PureLisp.List.Exprs
/*\semantics*/		Semantics list_one_plus = new Semantics() {
			public void f(ParseTree t, int l) {
				t.value = cons(t.child[l-2].value, t.child[l-1].value);
			}
		};
/*\off*/		put("List", new Object[][] {
			{"(", "Exprs", /*\semantics*/identity, /*\off*/")"}
		});
		put("Exprs", new Object[][] {
			{/*\semantics*/list_zero/*\off*/},
			{"Expr", "Exprs"/*\semantics*/, list_one_plus/*\off*/},
		});
//PureLisp.List.quote
/*\semantics*/		Semantics list_two = new Semantics() {
			public void f(ParseTree t, int l) {
				t.value = cons(t.child[l-2].value, cons(t.child[l-1].value, null));
			}
		};
/*\off*/		put("List", new Object[][] {
			{"(", "quote", "Expr", /*\semantics*/list_two, /*\off*/")"},
			{"(", "car", "Expr", /*\semantics*/list_two, /*\off*/")"},
			{"(", "cdr", "Expr", /*\semantics*/list_two, /*\off*/")"},
			{"(", "atom", "Expr", /*\semantics*/list_two, /*\off*/")"},
		});
//PureLisp.List.cons
/*\semantics*/		Semantics list_three = new Semantics() {
			public void f(ParseTree t, int l) {
				t.value = cons(t.child[l-3].value,
						cons(t.child[l-2].value, cons(t.child[l-1].value, null)));
			}
		};
/*\off*/		put("List", new Object[][] {
			{"(", "cons", "Expr", "Expr", /*\semantics*/list_three, /*\off*/")"},
			{"(", "eq", "Expr", "Expr", /*\semantics*/list_three, /*\off*/")"},
		});
//PureLisp.List.cond
		put("List", new Object[][] {
			{"(", "cond", "Cases", /*\semantics*/list_one_plus, /*\off*/")"}
		});
		put("Cases", new Object[][] {
			{/*\semantics*/list_zero/*\off*/},
			{"Case", "Cases"/*\semantics*/, list_one_plus/*\off*/},
		});
		put("Case", new Object[][] {
			{"(", "Expr", "Expr", /*\semantics*/list_two, /*\off*/")"}
		});
//PureLisp.List.AnonFunc
/*\semantics*/		Semantics list_three_of_five = new Semantics() {
			public void f(ParseTree t, int l) {
				t.value = cons(t.child[l-5].value,
						cons(t.child[l-3].value, cons(t.child[l-1].value, null)));
			}
		};
/*\off*/		put("List", new Object[][] {
			{"(", "AnonFunc", "Exprs", /*\semantics*/list_one_plus, /*\off*/")"}
		});
		put("AnonFunc", new Object[][] {
			{"(", "lambda", "(", "Formals", ")", "Expr", /*\semantics*/list_three_of_five, /*\off*/")"}
		});
		put("Formals", new Object[][] {
			{/*\semantics*/list_zero/*\off*/},
			{"IDENTIFIER", "Formals"/*\semantics*/, list_one_plus/*\off*/},
		});
//PureLisp.List.NamedFunc
		put("List", new Object[][] {
			{"(", "NamedFunc", "Exprs", /*\semantics*/list_one_plus, /*\off*/")"}
		});
		put("NamedFunc", new Object[][] {
			{"(", "label", "IDENTIFIER", "AnonFunc", /*\semantics*/list_three, /*\off*/")"}
		});
//PureLisp
	}

	public static void main(String[] arguments) throws Exception {
		new PureLisp().interpret(arguments);
	}
}