From 00a15a9e8c9bf578f1feccec53584ba0a3686b57 Mon Sep 17 00:00:00 2001
From: Alexander McCord <alex@mccord.dev>
Date: Fri, 24 May 2024 13:24:48 -0700
Subject: [PATCH] Add part of definition 2.2.

---
 EqSat/include/Luau/EGraph.h | 10 ++++++++++
 EqSat/src/EGraph.cpp        | 11 +++++++++++
 Sources.cmake               |  1 +
 3 files changed, 22 insertions(+)
 create mode 100644 EqSat/src/EGraph.cpp

diff --git a/EqSat/include/Luau/EGraph.h b/EqSat/include/Luau/EGraph.h
index 6d583142..e50cb3c4 100644
--- a/EqSat/include/Luau/EGraph.h
+++ b/EqSat/include/Luau/EGraph.h
@@ -34,6 +34,16 @@ struct EGraph final
     // TODO: static_assert L <: Language
     // TODO: static_assert N <: Analysis<L>
 
+    Id find(Id id) const;
+
+    // Per the egg paper, definition 2.2 (Canonicalization):
+    //
+    //   An e-node 𝑛 is canonical iff 𝑛 = canonicalize(𝑛), where
+    //   canonicalize(𝑓(𝑎1, 𝑎2, ...)) = 𝑓(find(𝑎1), find(𝑎2), ...).
+    //
+    // Doing so requires sketching out `Luau::EqSat::Language` which
+    // I want to do at a later time for the time being. Will revisit.
+
 private:
     /// A union-find data structure 𝑈 stores an equivalence relation over e-class ids.
     UnionFind unionfind;
diff --git a/EqSat/src/EGraph.cpp b/EqSat/src/EGraph.cpp
new file mode 100644
index 00000000..4d5194bb
--- /dev/null
+++ b/EqSat/src/EGraph.cpp
@@ -0,0 +1,11 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/EGraph.h"
+
+namespace Luau::EqSat {
+
+template<typename L, typename N>
+Id EGraph<L, N>::find(Id id) const {
+    return unionfind.find(id);
+}
+
+}
diff --git a/Sources.cmake b/Sources.cmake
index 8601fa28..6419aef4 100644
--- a/Sources.cmake
+++ b/Sources.cmake
@@ -302,6 +302,7 @@ target_sources(Luau.EqSat PRIVATE
     EqSat/include/Luau/Language.h
     EqSat/include/Luau/UnionFind.h
 
+    EqSat/src/EGraph.cpp
     EqSat/src/Id.cpp
     EqSat/src/UnionFind.cpp
 )