Add find_map with any, first, and last variants

src/iter/mod.rs

@@ -1504,7 +1504,7 @@ pub trait ParallelIterator: Sized + Send {
     /// just want the first match that discovered anywhere in the iterator,
     /// `find_any` is a better choice.
     ///
-    /// # Exmaples
+    /// # Examples
     ///
     /// ```
     /// use rayon::prelude::*;
@@ -1551,6 +1551,99 @@ pub trait ParallelIterator: Sized + Send {
         find_first_last::find_last(self, predicate)
     }
 
+    /// Applies the given predicate to the items in the parallel iterator
+    /// and returns **any** non-None result of the map operation.
+    ///
+    /// Once a non-None value is produced from the map operation, we will
+    /// attempt to stop processing the rest of the items in the iterator
+    /// as soon as possible.
+    ///
+    /// Note that this method only returns **some** item in the parallel
+    /// iterator that is not None from the map predicate. The item returned
+    /// may not be the **first** non-None value produced in the parallel
+    /// sequence, since the entire sequence is mapped over in parallel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    ///
+    /// let c = ["lol", "NaN", "5", "5"];
+    ///
+    /// let first_number = c.par_iter().find_map_first(|s| s.parse().ok());
+    ///
+    /// assert_eq!(first_number, Some(5));
+    /// ```
+    fn find_map_any<P, R>(self, predicate: P) -> Option<R>
+    where
+        P: Fn(Self::Item) -> Option<R> + Sync + Send,
+        R: Send,
+    {
+        self.filter_map(predicate).find_any(|_| true)
+    }
+
+    /// Applies the given predicate to the items in the parallel iterator and
+    /// returns the sequentially **first** non-None result of the map operation.
+    ///
+    /// Once a non-None value is produced from the map operation, all attempts
+    /// to the right of the match will be stopped, while attempts to the left
+    /// must continue in case an earlier match is found.
+    ///
+    /// Note that not all parallel iterators have a useful order, much like
+    /// sequential `HashMap` iteration, so "first" may be nebulous. If you
+    /// just want the first non-None value discovered anywhere in the iterator,
+    /// `find_map_any` is a better choice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    ///
+    /// let c = ["lol", "NaN", "2", "5"];
+    ///
+    /// let first_number = c.par_iter().find_map_first(|s| s.parse().ok());
+    ///
+    /// assert_eq!(first_number, Some(2));
+    /// ```
+    fn find_map_first<P, R>(self, predicate: P) -> Option<R>
+    where
+        P: Fn(Self::Item) -> Option<R> + Sync + Send,
+        R: Send,
+    {
+        self.filter_map(predicate).find_first(|_| true)
+    }
+
+    /// Applies the given predicate to the items in the parallel iterator and
+    /// returns the sequentially **last** non-None result of the map operation.
+    ///
+    /// Once a non-None value is produced from the map operation, all attempts
+    /// to the left of the match will be stopped, while attempts to the right
+    /// must continue in case a later match is found.
+    ///
+    /// Note that not all parallel iterators have a useful order, much like
+    /// sequential `HashMap` iteration, so "first" may be nebulous. If you
+    /// just want the first non-None value discovered anywhere in the iterator,
+    /// `find_map_any` is a better choice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use rayon::prelude::*;
+    ///
+    /// let c = ["lol", "NaN", "2", "5"];
+    ///
+    /// let first_number = c.par_iter().find_map_last(|s| s.parse().ok());
+    ///
+    /// assert_eq!(first_number, Some(5));
+    /// ```
+    fn find_map_last<P, R>(self, predicate: P) -> Option<R>
+    where
+        P: Fn(Self::Item) -> Option<R> + Sync + Send,
+        R: Send,
+    {
+        self.filter_map(predicate).find_last(|_| true)
+    }
+
     #[doc(hidden)]
     #[deprecated(note = "parallel `find` does not search in order -- use `find_any`, \\
                          `find_first`, or `find_last`")]

src/iter/plumbing/README.md

@@ -140,7 +140,7 @@ such as string characters.
 ## What on earth is `ProducerCallback`?
 
 We saw that when you call a parallel action method like
-`par_iter.reduce()`, that will creating a "reducing" consumer and then
+`par_iter.reduce()`, that will create a "reducing" consumer and then
 invoke `par_iter.drive_unindexed()` (or `par_iter.drive()`) as
 appropriate. This may create yet more consumers as we proceed up the
 parallel iterator chain. But at some point we're going to get to the

src/iter/test.rs

@@ -1271,6 +1271,50 @@ pub fn find_first_or_last() {
     assert_eq!(a.par_iter().position_last(|&x| x < 0), None);
 }
 
+#[test]
+pub fn find_map_first_or_last_or_any() {
+    let mut a: Vec<i32> = vec![];
+
+    assert!(a.par_iter().find_map_any(half_if_positive).is_none());
+    assert!(a.par_iter().find_map_first(half_if_positive).is_none());
+    assert!(a.par_iter().find_map_last(half_if_positive).is_none());
+
+    a = (-1024..-3).collect();
+
+    assert!(a.par_iter().find_map_any(half_if_positive).is_none());
+    assert!(a.par_iter().find_map_first(half_if_positive).is_none());
+    assert!(a.par_iter().find_map_last(half_if_positive).is_none());
+
+    assert!(a.par_iter().find_map_any(half_if_negative).is_some());
+    assert_eq!(
+        a.par_iter().find_map_first(half_if_negative),
+        Some(-512_i32)
+    );
+    assert_eq!(a.par_iter().find_map_last(half_if_negative), Some(-2_i32));
+
+    a.append(&mut (2..1025).collect());
+
+    assert!(a.par_iter().find_map_any(half_if_positive).is_some());
+    assert_eq!(a.par_iter().find_map_first(half_if_positive), Some(1_i32));
+    assert_eq!(a.par_iter().find_map_last(half_if_positive), Some(512_i32));
+
+    fn half_if_positive(x: &i32) -> Option<i32> {
+        if *x > 0 {
+            Some(x / 2)
+        } else {
+            None
+        }
+    }
+
+    fn half_if_negative(x: &i32) -> Option<i32> {
+        if *x < 0 {
+            Some(x / 2)
+        } else {
+            None
+        }
+    }
+}
+
 #[test]
 pub fn check_find_not_present() {
     let counter = AtomicUsize::new(0);