vendor/itertools/src/repeatn.rs

   1
   2 /// An iterator that produces *n* repetitions of an element.
   3 ///
   4 /// See [`repeat_n()`](../fn.repeat_n.html) for more information.
   5 #[must_use = "iterators are lazy and do nothing unless consumed"]
   6 #[derive(Debug)]
   7 pub struct RepeatN<A> {
   8     elt: Option<A>,
   9     n: usize,
  10 }
  11
  12 /// Create an iterator that produces `n` repetitions of `element`.
  13 pub fn repeat_n<A>(element: A, n: usize) -> RepeatN<A>
  14     where A: Clone,
  15 {
  16     if n == 0 {
  17         RepeatN { elt: None, n: n, }
  18     } else {
  19         RepeatN { elt: Some(element), n: n, }
  20     }
  21 }
  22
  23 impl<A> Iterator for RepeatN<A>
  24     where A: Clone
  25 {
  26     type Item = A;
  27
  28     fn next(&mut self) -> Option<Self::Item> {
  29         if self.n > 1 {
  30             self.n -= 1;
  31             self.elt.as_ref().cloned()
  32         } else {
  33             self.n = 0;
  34             self.elt.take()
  35         }
  36     }
  37
  38     fn size_hint(&self) -> (usize, Option<usize>) {
  39         (self.n, Some(self.n))
  40     }
  41 }
  42
  43 impl<A> DoubleEndedIterator for RepeatN<A>
  44     where A: Clone
  45 {
  46     #[inline]
  47     fn next_back(&mut self) -> Option<Self::Item> {
  48         self.next()
  49     }
  50 }
  51
  52 impl<A> ExactSizeIterator for RepeatN<A>
  53     where A: Clone
  54 {}