Add class-based oop example from [KS22 Example 2.8]

Minimal/Examples.lean

@@ -4,6 +4,215 @@ open Term
 open OptionalAttr
 open Reduce
 
+/-
+## References
+
+* [Nikolai Kudasov and Violetta Sim. 2023. Formalizing 𝜑-Calculus: A Purely Object-Oriented Calculus of Decorated Objects.][KS22]
+
+Class-based OOP example, modelling the following snippet (Java):
+
+class Base {
+  Integer g() { return h(); }
+  Integer h() { return 3; }
+}
+class Derived extends Base {
+  Integer f() { return 2 + this.g(); }
+  Integer h() { return 5; }
+}
+Derived d = new Derived();
+-/
+
+/-- [KS22, Example 2.8]-/
+def base : Term :=
+  obj (Bindings.cons
+      "new"
+      (by simp)
+      (attached
+        (Bindings.cons
+        "g"
+        (by simp)
+        (attached
+          (Bindings.cons
+          "this"
+          (by simp)
+          void
+          (Bindings.cons
+          "φ"
+          (by simp)
+          (attached
+            (dot
+              (app
+                (dot
+                  (dot
+                    (loc 0)
+                    "this"
+                  )
+                  "h"
+                )
+                "this"
+                (dot (loc 0) "this")
+              )
+              "φ"
+            )
+          )
+          Bindings.nil
+          )
+          )
+        )
+
+        (Binding.cons
+        "h"
+        (by simp)
+        (attached
+          (Bindings.cons
+          "this"
+          (by simp)
+          void
+          (Bindings.cons
+          "φ"
+          (by simp)
+          (attached (obj (Bindings.cons "3" (by simp) void Bindings.nil))) -- the base calculus does not have numbers, should be a 3
+          Bindings.nil
+          )
+          )
+        )
+        Bindings.nil
+        )
+        )
+      )
+      Binding.nil
+      )
+
+def derived : Term :=
+  obj (Bindings.cons
+      "new"
+      (by simp)
+      (attached (obj
+        (Bindings.cons
+        "φ"
+        (by simp)
+        (attached
+          (dot base "new")
+        )
+
+        (Binding.cons
+        "f"
+        (by simp)
+        (attached
+          (Bindings.cons
+          "this"
+          (by simp)
+          void
+          (Bindings.cons
+          "φ"
+          (by simp)
+          (attached
+            (app
+              (dot
+                (obj (Bindings.cons "2" (by simp) void Bindings.nil)) -- the base calculus does not have numbers, should be a 2
+                "add"
+              )
+              "n"
+              (dot
+                (app
+                  (dot
+                    (dot
+                      (loc 0)
+                      "this"
+                    )
+                    "g"
+                  )
+                  "this"
+                  (dot
+                    (loc 0)
+                    "this"
+                  )
+                )
+                "φ"
+              )
+            )
+          )
+          Bindings.nil
+          )
+          )
+        )
+
+        (Bindings.cons
+        "h"
+        (by simp)
+        (attached
+          (Bindings.cons
+          "this"
+          (by simp)
+          void
+          (Bindings.cons
+          "φ"
+          (by simp)
+          (attached (obj (Bindings.cons "5" (by simp) void Bindings.nil))) -- the base calculus does not have numbers, should be a 5
+          Bindings.nil
+          )
+          )
+        )
+        Bindings.nil
+        )
+        )
+        ))
+      )
+      Binding.nil
+      )
+
+def d : Term := dot derived "new"
+
+def invocation1
+  : d
+  ⇝
+  (obj  (Bindings.cons "φ" (by simp) (attached (dot base "new"))
+        (Binding.cons "f" (by simp) (attached
+          (Bindings.cons "this" (by simp) void
+          (Bindings.cons "φ" (by simp) (attached
+            (app
+              (dot (obj (Bindings.cons "2" (by simp) void Bindings.nil)) "add")
+              "n"
+              (dot (app (dot (dot (loc 0) "this") "g") "this" (dot (loc 0) "this")) "φ")
+            )
+          )
+          Bindings.nil))
+        )
+        (Bindings.cons "h" (by simp) (attached
+          (Bindings.cons "this" (by simp) void
+          (Bindings.cons "φ" (by simp) (attached (obj (Bindings.cons "5" (by simp) void Bindings.nil)))
+          Bindings.nil))
+        )
+        Bindings.nil))
+        )
+  )
+  := by
+    simp [substitute]
+    exact dot_c _ "new" _ (by simp) (by simp [lookup])
+
+-- def invocation
+--   : dot (app (dot d "f") "this" d) "φ" -- d.f(this ↦ d).φ     === Derived.new.f(this ↦ d).φ
+--   ⇝* app
+--         (dot (obj (Bindings.cons "2" (by simp) void Bindings.nil)) "add")
+--         "n"
+--         (dot (app (dot d "g") "this" d) "φ")
+--   :=
+--     ReflTransGen.head
+--     (dot_c _ "new" _ _ _)
+--     (ReflTransGen.head
+--     _
+--     (ReflTransGen.head
+--     _
+--     (ReflTransGen.head
+--     _
+--     (ReflTransGen.head
+--     _
+--     (ReflTransGen.head
+--     _
+--     ReflTransGen.refl
+--     )))))
+
+
 -- ⟦ a ↦ ⟦ ⟧ ⟧.a
 def example1 : Term :=
   dot