Merge #497 #498

497: impl FromParallelIterator<()> for () r=cuviper a=cuviper

This is more useful when combined with higher-level abstractions, like
collecting to a `Result<(), E>` where you only care about errors.

This is a parallel version of rust-lang/rust#45379.
Cc #496

498: FromParallelIterator and ParallelExtend Cow for String r=cuviper a=cuviper

Parallel version of rust-lang/rust#41449.

Author: bors[bot]

src/iter/extend.rs

@@ -1,5 +1,6 @@
 use super::{ParallelExtend, IntoParallelIterator, ParallelIterator};
 
+use std::borrow::Cow;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
 use std::hash::{BuildHasher, Hash};
 use std::collections::LinkedList;
@@ -262,6 +263,15 @@ impl ParallelExtend<String> for String {
     }
 }
 
+/// Extend a string with string slices from a parallel iterator.
+impl<'a> ParallelExtend<Cow<'a, str>> for String {
+    fn par_extend<I>(&mut self, par_iter: I)
+        where I: IntoParallelIterator<Item = Cow<'a, str>>
+    {
+        extend(self, par_iter, |string, list| string.reserve(str_len(list)));
+    }
+}
+
 
 /// Extend a deque with items from a parallel iterator.
 impl<T> ParallelExtend<T> for VecDeque<T>

src/iter/from_par_iter.rs

@@ -1,4 +1,4 @@
-use super::{FromParallelIterator, IntoParallelIterator, ParallelExtend};
+use super::{FromParallelIterator, IntoParallelIterator, ParallelIterator, ParallelExtend};
 
 use std::borrow::Cow;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
@@ -154,6 +154,15 @@ impl FromParallelIterator<String> for String {
     }
 }
 
+/// Collect string slices from a parallel iterator into a string.
+impl<'a> FromParallelIterator<Cow<'a, str>> for String {
+    fn from_par_iter<I>(par_iter: I) -> Self
+        where I: IntoParallelIterator<Item = Cow<'a, str>>
+    {
+        collect_extended(par_iter)
+    }
+}
+
 /// Collect an arbitrary `Cow` collection.
 ///
 /// Note, the standard library only has `FromIterator` for `Cow<'a, str>` and
@@ -170,3 +179,26 @@ impl<'a, C: ?Sized, T> FromParallelIterator<T> for Cow<'a, C>
         Cow::Owned(C::Owned::from_par_iter(par_iter))
     }
 }
+
+/// Collapses all unit items from a parallel iterator into one.
+///
+/// This is more useful when combined with higher-level abstractions, like
+/// collecting to a `Result<(), E>` where you only care about errors:
+///
+/// ```
+/// use std::io::*;
+/// use rayon::prelude::*;
+///
+/// let data = vec![1, 2, 3, 4, 5];
+/// let res: Result<()> = data.par_iter()
+///     .map(|x| writeln!(stdout(), "{}", x))
+///     .collect();
+/// assert!(res.is_ok());
+/// ```
+impl FromParallelIterator<()> for () {
+    fn from_par_iter<I>(par_iter: I) -> Self
+        where I: IntoParallelIterator<Item = ()>
+    {
+        par_iter.into_par_iter().for_each(|()| {})
+    }
+}