Add collect tests for tuple FromParallelIterator

Author: cuviper

src/iter/mod.rs

@@ -1966,6 +1966,79 @@ pub trait ParallelIterator: Sized + Send {
     ///
     /// assert_eq!(sync_vec, async_vec);
     /// ```
+    ///
+    /// You can collect a pair of collections like [`unzip`](#method.unzip)
+    /// for paired items:
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    ///
+    /// let a = [(0, 1), (1, 2), (2, 3), (3, 4)];
+    /// let (first, second): (Vec<_>, Vec<_>) = a.into_par_iter().collect();
+    ///
+    /// assert_eq!(first, [0, 1, 2, 3]);
+    /// assert_eq!(second, [1, 2, 3, 4]);
+    /// ```
+    ///
+    /// Or like [`partition_map`](#method.partition_map) for `Either` items:
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    /// use rayon::iter::Either;
+    ///
+    /// let (left, right): (Vec<_>, Vec<_>) = (0..8).into_par_iter().map(|x| {
+    ///     if x % 2 == 0 {
+    ///         Either::Left(x * 4)
+    ///     } else {
+    ///         Either::Right(x * 3)
+    ///     }
+    /// }).collect();
+    ///
+    /// assert_eq!(left, [0, 8, 16, 24]);
+    /// assert_eq!(right, [3, 9, 15, 21]);
+    /// ```
+    ///
+    /// You can even collect an arbitrarily-nested combination of pairs and `Either`:
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    /// use rayon::iter::Either;
+    ///
+    /// let (first, (left, right)): (Vec<_>, (Vec<_>, Vec<_>))
+    ///     = (0..8).into_par_iter().map(|x| {
+    ///         if x % 2 == 0 {
+    ///             (x, Either::Left(x * 4))
+    ///         } else {
+    ///             (-x, Either::Right(x * 3))
+    ///         }
+    ///     }).collect();
+    ///
+    /// assert_eq!(first, [0, -1, 2, -3, 4, -5, 6, -7]);
+    /// assert_eq!(left, [0, 8, 16, 24]);
+    /// assert_eq!(right, [3, 9, 15, 21]);
+    /// ```
+    ///
+    /// All of that can _also_ be combined with short-circuiting collection of
+    /// `Result` or `Option` types:
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    /// use rayon::iter::Either;
+    ///
+    /// let result: Result<(Vec<_>, (Vec<_>, Vec<_>)), _>
+    ///     = (0..8).into_par_iter().map(|x| {
+    ///         if x > 5 {
+    ///             Err(x)
+    ///         } else if x % 2 == 0 {
+    ///             Ok((x, Either::Left(x * 4)))
+    ///         } else {
+    ///             Ok((-x, Either::Right(x * 3)))
+    ///         }
+    ///     }).collect();
+    ///
+    /// let error = result.unwrap_err();
+    /// assert!(error == 6 || error == 7);
+    /// ```
     fn collect<C>(self) -> C
     where
         C: FromParallelIterator<Self::Item>,