s.entries[s.head] = a
	if s.size < s.max {
		s.size++
	}
}

// NthPreviousEntry returns the value passed to the nth previous call to Add.
// If n is zero then the immediately prior value is returned, if one, then the
// next most recent, and so on. If such an element doesn't exist then ok is
// false.
func (s *stRingBuffer) NthPreviousEntry(n int) (value string, ok bool) {
	if n < 0 || n >= s.size {
		return "", false
	}