From 45440197defab29b6ff408b3e5a7a51d49de7972 Mon Sep 17 00:00:00 2001
From: David Robertson <davidr@element.io>
Date: Wed, 1 Jun 2022 15:02:31 +0100
Subject: [PATCH] Better description of the mainline of a PL event.

---
 content/rooms/fragments/v2-state-res.md | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/content/rooms/fragments/v2-state-res.md b/content/rooms/fragments/v2-state-res.md
index e666d7f8..cd73e2ad 100644
--- a/content/rooms/fragments/v2-state-res.md
+++ b/content/rooms/fragments/v2-state-res.md
@@ -82,10 +82,15 @@ selecting, among all the candidate vertices, the smallest vertex using
 the above comparison relation.
 
 **Mainline ordering.**
-Given an `m.room.power_levels` event *P*, the *mainline of* *P* is the
-list of events generated by starting with *P* and recursively taking the
-`m.room.power_levels` events from the `auth_events`, ordered such that
-*P* is last. Given another event *e*, the *closest mainline event to*
+Let *P* = *P*<sub>0</sub> be an `m.room.power_levels` event.
+Starting with *i* = 0, repeatedly fetch *P*<sub>*i*+1</sub>, the
+`m.room.power_levels` event in the `auth_events` of *P<sub>i</sub>*.
+Increment *i* and repeat until *P<sub>i</sub>* has no `m.room.power_levels`
+event in its `auth_events`.
+The *mainline of P*<sub>0</sub> is the list of events
+    [*P*<sub>n</sub> , ... , *P*<sub>1</sub>, *P*<sub>0</sub>].
+
+Given another event *e*, the *closest mainline event to*
 *e* is the first event encountered in the mainline when iteratively
 descending through the `m.room.power_levels` events in the `auth_events`
 starting at *e*. If no mainline event is encountered when iteratively