From f27d604d93ce583d4404e1874664e08382ea2f00 Mon Sep 17 00:00:00 2001
From: JSDurand <mmemmew@gmail.com>
Date: Fri, 6 Jan 2023 23:42:28 +0800
Subject: Save before system restart.

I am about to re-start my system, so I save before any crashes
happen.
---
 graph/src/lib.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'graph/src/lib.rs')

diff --git a/graph/src/lib.rs b/graph/src/lib.rs
index 79f9646..26159c6 100644
--- a/graph/src/lib.rs
+++ b/graph/src/lib.rs
@@ -214,6 +214,19 @@ impl<T: Hash + Eq + PartialEq + Clone + Copy + Ord + PartialOrd + Display + Debu
 {
 }
 
+/// A parents-knowing graph can return an iterator of parents for any
+/// node.
+pub trait ParentsGraph: Graph {
+    /// The type of an iterator that goes through the parents of a
+    /// node.
+    type Iter<'a>: Iterator<Item = usize> + 'a
+    where
+        Self: 'a;
+
+    /// Return an iterator of parents for a node.
+    fn parents_of(&self, node_id: usize) -> Result<<Self as ParentsGraph>::Iter<'_>, Error>;
+}
+
 /// A labelled graph is just a graph with labels associated to
 /// vertices and / or edges.
 ///
-- 
cgit v1.2.3-18-g5258