vendor/itertools/src/zip_eq_impl.rs

   1 use super::size_hint;
   2
   3 /// An iterator which iterates two other iterators simultaneously
   4 ///
   5 /// See [`.zip_eq()`](../trait.Itertools.html#method.zip_eq) for more information.
   6 #[derive(Clone, Debug)]
   7 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
   8 pub struct ZipEq<I, J> {
   9     a: I,
  10     b: J,
  11 }
  12
  13 /// Iterate `i` and `j` in lock step.
  14 ///
  15 /// **Panics** if the iterators are not of the same length.
  16 ///
  17 /// `IntoIterator` enabled version of `i.zip_eq(j)`.
  18 ///
  19 /// ```
  20 /// use itertools::zip_eq;
  21 ///
  22 /// let data = [1, 2, 3, 4, 5];
  23 /// for (a, b) in zip_eq(&data[..data.len() - 1], &data[1..]) {
  24 ///     /* loop body */
  25 /// }
  26 /// ```
  27 pub fn zip_eq<I, J>(i: I, j: J) -> ZipEq<I::IntoIter, J::IntoIter>
  28     where I: IntoIterator,
  29           J: IntoIterator
  30 {
  31     ZipEq {
  32         a: i.into_iter(),
  33         b: j.into_iter(),
  34     }
  35 }
  36
  37 impl<I, J> Iterator for ZipEq<I, J>
  38     where I: Iterator,
  39           J: Iterator
  40 {
  41     type Item = (I::Item, J::Item);
  42
  43     fn next(&mut self) -> Option<Self::Item> {
  44         match (self.a.next(), self.b.next()) {
  45             (None, None) => None,
  46             (Some(a), Some(b)) => Some((a, b)),
  47             (None, Some(_)) | (Some(_), None) =>
  48             panic!("itertools: .zip_eq() reached end of one iterator before the other")
  49         }
  50     }
  51
  52     fn size_hint(&self) -> (usize, Option<usize>) {
  53         size_hint::min(self.a.size_hint(), self.b.size_hint())
  54     }
  55 }
  56
  57 impl<I, J> ExactSizeIterator for ZipEq<I, J>
  58     where I: ExactSizeIterator,
  59           J: ExactSizeIterator
  60 {}