func Cdadr(x interface{}) interface{} {
	return Cdar(Cdr(x))
}
Cdadr returns Cdr(Car(Cdr(x)))
package list
func Car(x interface{}) interface{} {
	pair, _ := x.(*Pair)
	if pair == nil {
		return nil
	}
	return pair.Car
}
func Cdr(x interface{}) interface{} {
	pair, _ := x.(*Pair)
	if pair == nil {
		return nil
	}
	return pair.Cdr
}
func Caar(x interface{}) interface{} {
	return Car(Car(x))
}
func Cadr(x interface{}) interface{} {
	return Car(Cdr(x))
}
func Cdar(x interface{}) interface{} {
	return Cdr(Car(x))
}
func Cddr(x interface{}) interface{} {
	return Cdr(Cdr(x))
}
func Caaar(x interface{}) interface{} {
	return Caar(Car(x))
}
func Caadr(x interface{}) interface{} {
	return Caar(Cdr(x))
}
func Cadar(x interface{}) interface{} {
	return Cadr(Car(x))
}
func Caddr(x interface{}) interface{} {
	return Cadr(Cdr(x))
}
func Cdaar(x interface{}) interface{} {
	return Cdar(Car(x))
}