func (l *List) PushBackLoop(v int, eNum int) *Element {
	e := &Element{v, l.GetElement(eNum)}
	if l.N == 0 {
		panic("size is zero")
	} else {
		l.tail.Next = e
	}
	l.tail = e
	l.N++
	return e
}
//PushBackLoop inserts a new element e pointing the element whose number equals eNum

PushBackLoop inserts a new element e pointing the element whose number equals eNum
// PushBackLoop inserts a new element e pointing the element whose number equals eNum
func (l *List) PushBackLoop(v int, eNum int) *Element {
	e := &Element{v, l.GetElement(eNum)}
	if l.N == 0 {
		panic("size is zero")
	} else {
		l.tail.Next = e
	}
	l.tail = e
	l.N++
	return e
}
func ( l * List ) PushBackLoop ( v int , eNum int ) * Element { e := & Element { v , l . GetElement ( eNum ) } if l . N == 0 { panic ( " " ) } else { l . tail . Next = e } l . tail = e l . N ++ return e }
PushBackLoop inserts a new element e pointing the element whose number equals eNum
PushBackLoop inserts a new element e pointing the element whose number equals eNum