vendor/itertools/src/concat_impl.rs

   1 use crate::Itertools;
   2
   3 /// Combine all an iterator's elements into one element by using [`Extend`].
   4 ///
   5 /// [`IntoIterator`]-enabled version of [`Itertools::concat`].
   6 ///
   7 /// This combinator will extend the first item with each of the rest of the
   8 /// items of the iterator. If the iterator is empty, the default value of
   9 /// `I::Item` is returned.
  10 ///
  11 /// ```rust
  12 /// use itertools::concat;
  13 ///
  14 /// let input = vec![vec![1], vec![2, 3], vec![4, 5, 6]];
  15 /// assert_eq!(concat(input), vec![1, 2, 3, 4, 5, 6]);
  16 /// ```
  17 pub fn concat<I>(iterable: I) -> I::Item
  18 where
  19     I: IntoIterator,
  20     I::Item: Extend<<<I as IntoIterator>::Item as IntoIterator>::Item> + IntoIterator + Default,
  21 {
  22     #[allow(deprecated)] //TODO: once msrv hits 1.51. replace `fold1` with `reduce`
  23     iterable
  24         .into_iter()
  25         .fold1(|mut a, b| {
  26             a.extend(b);
  27             a
  28         })
  29         .unwrap_or_default()
  30 }