Definition 2.1.1.

EqSat/include/Luau/EGraph.h

@@ -0,0 +1,52 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/DenseHash.h"
+#include "Luau/Id.h"
+#include "Luau/UnionFind.h"
+
+#include <utility>
+#include <vector>
+
+namespace Luau::EqSat
+{
+
+/// Each e-class is a set of e-nodes representing equivalent terms from a given language,
+/// and an e-node is a function symbol paired with a list of children e-classes.
+template<typename L, typename D>
+struct EClass {
+    Id id;
+    std::vector<L> nodes;
+    D data;
+    std::vector<std::pair<L, Id>> parents;
+};
+
+/// In Definition 2.1, an EGraph is composed with a tuple (U, M, H) where
+/// - U: [`EGraph::u`]
+/// - M: [`EGraph::m`]
+/// - H: [`EGraph::h`]
+///
+/// See <https://arxiv.org/pdf/2004.03082>.
+template<typename L, typename N>
+struct EGraph
+{
+    // TODO: static_assert L <: Language
+    // TODO: static_assert N <: Analysis<L>
+
+private:
+    /// A union-find data structure 𝑈 stores an equivalence relation over e-class ids.
+    UnionFind u;
+
+    /// The e-class map 𝑀 maps e-class ids to e-classes. All equivalent e-class ids map to the same
+    /// e-class, i.e., 𝑎 ≡id 𝑏 iff 𝑀[𝑎] is the same set as 𝑀[𝑏]. An e-class id 𝑎 is said to refer to the
+    /// e-class 𝑀[find(𝑎)].
+    DenseHashMap<Id, EClass<L, typename N::Data>> m;
+
+    /// The hashcons 𝐻 is a map from e-nodes to e-node ids.
+    ///
+    /// Author note: the paper says this maps from e-nodes to e-class ids, but the
+    /// corresponding map in the egg crate called `memo`, they map it to e-node ids?
+    DenseHashMap<EClass<L, typename N::Data>, Id> h;
+};
+
+} // namespace Luau::EqSat

EqSat/include/Luau/Language.h

@@ -0,0 +1,15 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Id.h"
+
+namespace Luau::EqSat
+{
+
+template<typename L>
+struct Language
+{
+
+};
+
+} // namespace Luau::EqSat

EqSat/include/Luau/UnionFind.h

@@ -0,0 +1,12 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+namespace Luau::EqSat
+{
+
+/// See <https://dl.acm.org/doi/pdf/10.1145/321879.321884>.
+struct UnionFind
+{
+};
+
+} // namespace Luau::EqSat

EqSat/src/UnionFind.cpp

@@ -0,0 +1,9 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/UnionFind.h"
+
+namespace Luau::EqSat
+{
+
+
+
+} // namespace Luau::EqSat

Sources.cmake

@@ -297,9 +297,13 @@ target_sources(Luau.Analysis PRIVATE
 
 # Luau.Analysis Sources
 target_sources(Luau.EqSat PRIVATE
+    EqSat/include/Luau/EGraph.h
     EqSat/include/Luau/Id.h
+    EqSat/include/Luau/Language.h
+    EqSat/include/Luau/UnionFind.h
 
     EqSat/src/Id.cpp
+    EqSat/src/UnionFind.cpp
 )
 
 # Luau.VM Sources