From cdd1d99ef83c5ab5887b957c1210ca72ec426f8f Mon Sep 17 00:00:00 2001
From: Frank McSherry <fmcsherry@me.com>
Date: Fri, 18 Mar 2022 09:38:24 -0400
Subject: [PATCH 1/2] Add option conversions for totally ordered antichains

---
 timely/src/progress/frontier.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/timely/src/progress/frontier.rs b/timely/src/progress/frontier.rs
index 77fd5a120..6a707ccc5 100644
--- a/timely/src/progress/frontier.rs
+++ b/timely/src/progress/frontier.rs
@@ -229,6 +229,19 @@ impl<T: Clone> Clone for Antichain<T> {
 
 impl<T: TotalOrder> TotalOrder for Antichain<T> { }
 
+impl<T: TotalOrder> Antichain<T> {
+    /// Convert to the at most one element the antichain contains.
+    pub fn into_option(mut self) -> Option<T> {
+        debug_assert!(self.len() <= 1);
+        self.elements.pop()
+    }
+    /// Return a reference to the at most one element the antichain contains.
+    pub fn as_option(&self) -> Option<&T> {
+        debug_assert!(self.len() <= 1);
+        self.elements.last()
+    }
+}
+
 impl<T: Ord+std::hash::Hash> std::hash::Hash for Antichain<T> {
     fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
         let mut temp = self.elements.iter().collect::<Vec<_>>();
@@ -711,6 +724,16 @@ impl<'a, T: PartialOrder> PartialOrder for AntichainRef<'a, T> {
     }
 }
 
+impl<'a, T: TotalOrder> TotalOrder for AntichainRef<'a, T> { }
+
+impl<'a, T: TotalOrder> AntichainRef<'a, T> {
+    /// Return a reference to the at most one element the antichain contains.
+    pub fn as_option(&self) -> Option<&T> {
+        debug_assert!(self.len() <= 1);
+        self.frontier.last()
+    }
+}
+
 impl<'a, T> ::std::ops::Deref for AntichainRef<'a, T> {
     type Target = [T];
     fn deref(&self) -> &Self::Target {

From d3f0ea6670dc331e60d3ea51744a595e26bc7b8c Mon Sep 17 00:00:00 2001
From: Frank McSherry <fmcsherry@me.com>
Date: Fri, 18 Mar 2022 10:28:56 -0400
Subject: [PATCH 2/2] Add FromIterator implementations

---
 timely/src/progress/frontier.rs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/timely/src/progress/frontier.rs b/timely/src/progress/frontier.rs
index 6a707ccc5..ea52ba63e 100644
--- a/timely/src/progress/frontier.rs
+++ b/timely/src/progress/frontier.rs
@@ -116,6 +116,17 @@ impl<T: PartialOrder> Antichain<T> {
     }
 }
 
+impl<T: PartialOrder> std::iter::FromIterator<T> for Antichain<T> {
+    fn from_iter<I>(iterator: I) -> Self
+    where
+        I: IntoIterator<Item=T>
+    {
+        let mut result = Self::new();
+        result.extend(iterator);
+        result
+    }
+}
+
 impl<T> Antichain<T> {
 
     /// Creates a new empty `Antichain`.
@@ -623,6 +634,20 @@ impl<'a, T: PartialOrder+Ord+Clone> From<AntichainRef<'a, T>> for MutableAnticha
     }
 }
 
+impl<T> std::iter::FromIterator<(T, i64)> for MutableAntichain<T>
+where
+    T: Clone + PartialOrder + Ord,
+{
+    fn from_iter<I>(iterator: I) -> Self
+    where
+        I: IntoIterator<Item=(T, i64)>,
+    {
+        let mut result = Self::new();
+        result.update_iter(iterator);
+        result
+    }
+}
+
 /// A wrapper for elements of an antichain.
 #[derive(Debug)]
 pub struct AntichainRef<'a, T: 'a> {