Set Rules Episode VIII: The First Macro

1 files changed, 7 insertions, 0 deletions

diff --git a/src/eval/node.rs b/src/eval/node.rs
index a04fe84b..acdf4ed6 100644
--- a/src/eval/node.rs
+++ b/src/eval/node.rs
@@ -1,6 +1,7 @@
 use std::convert::TryFrom;
 use std::fmt::Debug;
 use std::hash::Hash;
+use std::iter::Sum;
 use std::mem;
 use std::ops::{Add, AddAssign};
 
@@ -127,6 +128,12 @@ impl AddAssign for Node {
     }
 }
 
+impl Sum for Node {
+    fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
+        Self::Sequence(iter.map(|n| (n, Styles::new())).collect())
+    }
+}
+
 /// Packs a [`Node`] into a flow or whole document.
 struct Packer {
     /// Whether this packer produces the top-level document.