public class schemecompat {

    /* SCHEME "COMPATIBILITY" FUNCTIONS */
    static void display( Object x ) { System.out.print(x.toString()); }
    static void newline() { System.out.println(); }
    static class Pair { 
	Object car; 
	Object cdr; 
	public boolean equals( Object x ) {
	    return (x instanceof Pair) && 
		((Pair)x).car.equals(this.car) &&
		((Pair)x).cdr.equals(this.cdr);
	}
    }
    static class Null { } 
    static Object empty = new Null();
    static Object falseObj  = new Boolean(false);
    static Object minusChar = new Character('-');
    static Object digits[] = { new Character('0'),
			       new Character('1'),
			       new Character('2'),
			       new Character('3'),
			       new Character('4'),
			       new Character('5'),
			       new Character('6'),
			       new Character('7'),
			       new Character('8'),
			       new Character('9') };
    static Pair cons(Object a, Object d) { 
	Pair p = new Pair(); p.car = a; p.cdr = d; return p; 
    }
    static Object car(Object x) { return ((Pair)x).car; }
    static Object cdr(Object x) { return ((Pair)x).cdr; }
    static boolean isNull(Object x) { return (x instanceof Null); }
    static Object append( Object x, Object y ) {
	return (isNull(x) ? y : cons( car(x), append( cdr(x), y )));
    }
    static Object stringToList( Object x ) {
	if (((String)x).length() == 0)
	    return empty;
	else
	    return cons( new Character( ((String)x).charAt(0) ),
			 stringToList( ((String)x).substring(1) ));
    }
}