From 0da5e49d80ddbfcf8b4303cb4f62d0dec3e36f7b Mon Sep 17 00:00:00 2001
From: Dan Vanderkam <danvdk@gmail.com>
Date: Fri, 2 Feb 2024 17:21:15 -0500
Subject: [PATCH 1/5] inherit methods

---
 examples/chapter13/boston-creme.lox |  9 +++++++++
 src/ast.ts                          |  1 +
 src/interpreter.ts                  | 13 ++++++++++++-
 src/lox-class.ts                    | 13 ++++++++++---
 src/parser.ts                       | 21 ++++++++++++++++++---
 src/resolver.ts                     | 10 ++++++++++
 6 files changed, 60 insertions(+), 7 deletions(-)
 create mode 100644 examples/chapter13/boston-creme.lox

diff --git a/examples/chapter13/boston-creme.lox b/examples/chapter13/boston-creme.lox
new file mode 100644
index 0000000..916dbfb
--- /dev/null
+++ b/examples/chapter13/boston-creme.lox
@@ -0,0 +1,9 @@
+class Doughnut {
+  cook() {
+    print "Fry until golden brown.";
+  }
+}
+
+class BostonCream < Doughnut {}
+
+BostonCream().cook();
\ No newline at end of file
diff --git a/src/ast.ts b/src/ast.ts
index 1fec362..e28daa9 100644
--- a/src/ast.ts
+++ b/src/ast.ts
@@ -113,6 +113,7 @@ export interface Return {
 export interface Class {
 	kind: "class";
 	name: Token;
+	superclass: VarExpr | null;
 	methods: Func[];
 }
 
diff --git a/src/interpreter.ts b/src/interpreter.ts
index 5415e6f..d1b11d8 100644
--- a/src/interpreter.ts
+++ b/src/interpreter.ts
@@ -161,6 +161,17 @@ export class Interpreter {
 	}
 
 	class(stmt: Class): void {
+		let superclass = null;
+		if (stmt.superclass) {
+			superclass = this.evaluate(stmt.superclass);
+			if (!(superclass instanceof LoxClass)) {
+				throw new RuntimeError(
+					stmt.superclass.name,
+					"Superclass must be a class.",
+				);
+			}
+		}
+
 		this.#environment.define(stmt.name.lexeme, null);
 		const methods = new Map<string, LoxFunction>();
 		for (const method of stmt.methods) {
@@ -171,7 +182,7 @@ export class Interpreter {
 			);
 			methods.set(method.name.lexeme, func);
 		}
-		const klass = new LoxClass(stmt.name.lexeme, methods);
+		const klass = new LoxClass(stmt.name.lexeme, superclass, methods);
 		this.#environment.assign(stmt.name, klass);
 	}
 
diff --git a/src/lox-class.ts b/src/lox-class.ts
index 908a58c..b32a905 100644
--- a/src/lox-class.ts
+++ b/src/lox-class.ts
@@ -10,11 +10,17 @@ import { LoxValue } from "./lox-value.js";
 export class LoxClass extends LoxCallable {
 	#methods: Map<string, LoxFunction>;
 	name: string;
+	superclass: LoxClass | null;
 
-	constructor(name: string, methods: Map<string, LoxFunction>) {
+	constructor(
+		name: string,
+		superclass: LoxClass | null,
+		methods: Map<string, LoxFunction>,
+	) {
 		super();
 		this.name = name;
 		this.#methods = methods;
+		this.superclass = superclass;
 	}
 
 	arity(): number {
@@ -31,8 +37,9 @@ export class LoxClass extends LoxCallable {
 		return instance;
 	}
 
-	findMethod(name: string) {
-		return this.#methods.get(name);
+	findMethod(name: string): LoxFunction | undefined {
+		const meth = this.#methods.get(name);
+		return meth ?? this.superclass?.findMethod(name);
 	}
 
 	toString() {
diff --git a/src/parser.ts b/src/parser.ts
index bf42e15..abf1c6e 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -1,7 +1,7 @@
 // Grammar:
 // program        → declaration* EOF ;
 // declaration    → classDecl | funDecl | varDecl | statement ;
-// classDecl      → "class" IDENTIFIER "{" function* "}" ;
+// classDecl      → "class" IDENTIFIER ( "<" IDENTIFIER ) "{" function* "}" ;
 // funDecl        → "fun" function ;
 // function       → IDENTIFIER "(" parameters? ")" block ;
 // varDecl        → "var" IDENTIFIER ( "=" expression )? ";" ;
@@ -28,7 +28,15 @@
 //                | "(" expression ")" ;
 //                | IDENTIFIER ;
 
-import { Expr, Expression, Func, Print, Stmt, VarStmt } from "./ast.js";
+import {
+	Expr,
+	Expression,
+	Func,
+	Print,
+	Stmt,
+	VarExpr,
+	VarStmt,
+} from "./ast.js";
 import { errorOnToken } from "./main.js";
 import { Token } from "./token.js";
 import { TokenType } from "./token-type.js";
@@ -121,13 +129,20 @@ export function parse(tokens: Token[]) {
 	// classDecl      → "class" IDENTIFIER "{" function* "}" ;
 	const classDecl = (): Stmt => {
 		const name = consume("identifier", "Expect class name.");
+
+		let superclass: VarExpr | null = null;
+		if (match("<")) {
+			consume("identifier", "Expect superclass name.");
+			superclass = { kind: "var-expr", name: previous() };
+		}
+
 		consume("{", "Expect '{' before class body.");
 		const methods = [];
 		while (!check("}") && !isAtEnd()) {
 			methods.push(func("method"));
 		}
 		consume("}", "Expect '}' after class body.");
-		return { kind: "class", methods, name };
+		return { kind: "class", methods, name, superclass };
 	};
 
 	// funDecl        → "fun" function ;
diff --git a/src/resolver.ts b/src/resolver.ts
index c2b0530..7ebf9a7 100644
--- a/src/resolver.ts
+++ b/src/resolver.ts
@@ -92,6 +92,16 @@ export function makeResolver(interpreter: Interpreter) {
 			currentClass = "class";
 			declare(stmt.name);
 			define(stmt.name);
+			if (stmt.superclass && stmt.name.lexeme === stmt.superclass.name.lexeme) {
+				// What about circular inheritance?
+				errorOnToken(
+					stmt.superclass.name,
+					"A class can't inherit from itself.",
+				);
+			}
+			if (stmt.superclass) {
+				resolveExpr(stmt.superclass);
+			}
 			beginScope();
 			// TODO: write a peek() to enforce that -1 works.
 			scopes.at(-1)?.set("this", true);

From aa68670646882f76b89555ecde762d9bbda4d3eb Mon Sep 17 00:00:00 2001
From: Dan Vanderkam <danvdk@gmail.com>
Date: Fri, 2 Feb 2024 17:42:16 -0500
Subject: [PATCH 2/5] implement super

---
 examples/chapter13/boston-creme-super.lox     | 14 +++++++++
 examples/chapter13/invalid-super-in-class.lox |  6 ++++
 .../chapter13/invalid-super-top-level.lox     |  1 +
 examples/chapter13/which-super.lox            | 19 ++++++++++++
 src/ast-printer.ts                            |  1 +
 src/ast.ts                                    |  7 +++++
 src/environment.ts                            |  6 ++--
 src/interpreter.ts                            | 30 +++++++++++++++++++
 src/parser.ts                                 |  9 ++++--
 src/resolver.ts                               | 23 +++++++++++++-
 10 files changed, 110 insertions(+), 6 deletions(-)
 create mode 100644 examples/chapter13/boston-creme-super.lox
 create mode 100644 examples/chapter13/invalid-super-in-class.lox
 create mode 100644 examples/chapter13/invalid-super-top-level.lox
 create mode 100644 examples/chapter13/which-super.lox

diff --git a/examples/chapter13/boston-creme-super.lox b/examples/chapter13/boston-creme-super.lox
new file mode 100644
index 0000000..79ad64b
--- /dev/null
+++ b/examples/chapter13/boston-creme-super.lox
@@ -0,0 +1,14 @@
+class Doughnut {
+  cook() {
+    print "Fry until golden brown.";
+  }
+}
+
+class BostonCream < Doughnut {
+  cook() {
+    super.cook();
+    print "Pipe full of custard and coat with chocolate.";
+  }
+}
+
+BostonCream().cook();
diff --git a/examples/chapter13/invalid-super-in-class.lox b/examples/chapter13/invalid-super-in-class.lox
new file mode 100644
index 0000000..76f7e5d
--- /dev/null
+++ b/examples/chapter13/invalid-super-in-class.lox
@@ -0,0 +1,6 @@
+class Eclair {
+  cook() {
+    super.cook();
+    print "Pipe full of crème pâtissière.";
+  }
+}
\ No newline at end of file
diff --git a/examples/chapter13/invalid-super-top-level.lox b/examples/chapter13/invalid-super-top-level.lox
new file mode 100644
index 0000000..284bedf
--- /dev/null
+++ b/examples/chapter13/invalid-super-top-level.lox
@@ -0,0 +1 @@
+super.notEvenInAClass();
diff --git a/examples/chapter13/which-super.lox b/examples/chapter13/which-super.lox
new file mode 100644
index 0000000..6dd7f1c
--- /dev/null
+++ b/examples/chapter13/which-super.lox
@@ -0,0 +1,19 @@
+class A {
+  method() {
+    print "A method";
+  }
+}
+
+class B < A {
+  method() {
+    print "B method";
+  }
+
+  test() {
+    super.method();
+  }
+}
+
+class C < B {}
+
+C().test();
\ No newline at end of file
diff --git a/src/ast-printer.ts b/src/ast-printer.ts
index a55dd87..317a2bc 100644
--- a/src/ast-printer.ts
+++ b/src/ast-printer.ts
@@ -38,6 +38,7 @@ export const astPrinter: ExpressionVisitor<string> & StmtVisitor<string> = {
 	print: (stmt) => parenthesize("print", stmt.expression),
 	return: (stmt) => parenthesize("return", ...(stmt.value ? [stmt.value] : [])),
 	set: (expr) => parenthesize("set", expr.object, expr.name.lexeme, expr.value),
+	super: () => "super",
 	this: () => parenthesize("this"),
 	unary: (expr) => parenthesize(expr.operator.lexeme, expr.right),
 	"var-expr": (expr) => String(expr.name.literal),
diff --git a/src/ast.ts b/src/ast.ts
index e28daa9..610650e 100644
--- a/src/ast.ts
+++ b/src/ast.ts
@@ -124,6 +124,12 @@ export interface SetExpr {
 	value: Expr;
 }
 
+export interface Super {
+	kind: "super";
+	keyword: Token;
+	method: Token;
+}
+
 export type Expr =
 	| Assign
 	| Binary
@@ -133,6 +139,7 @@ export type Expr =
 	| Literal
 	| Logical
 	| SetExpr
+	| Super
 	| This
 	| Unary
 	| VarExpr;
diff --git a/src/environment.ts b/src/environment.ts
index a01b765..1872640 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -3,19 +3,19 @@ import { LoxValue } from "./lox-value.js";
 import { Token } from "./token.js";
 
 export class Environment {
-	#enclosing?: Environment;
 	#values: Map<string, LoxValue>;
+	enclosing?: Environment;
 
 	constructor(enclosing?: Environment) {
 		this.#values = new Map();
-		this.#enclosing = enclosing;
+		this.enclosing = enclosing;
 	}
 
 	ancestor(distance: number): Environment {
 		// eslint-disable-next-line @typescript-eslint/no-this-alias
 		let env: Environment = this;
 		for (let i = 0; i < distance; i++) {
-			const enclosing = env.#enclosing;
+			const enclosing = env.enclosing;
 			if (!enclosing) {
 				throw new Error("Tried to go past last ancestor!");
 			}
diff --git a/src/interpreter.ts b/src/interpreter.ts
index d1b11d8..535495d 100644
--- a/src/interpreter.ts
+++ b/src/interpreter.ts
@@ -173,6 +173,11 @@ export class Interpreter {
 		}
 
 		this.#environment.define(stmt.name.lexeme, null);
+		if (superclass) {
+			this.#environment = new Environment(this.#environment);
+			this.#environment.define("super", superclass);
+		}
+
 		const methods = new Map<string, LoxFunction>();
 		for (const method of stmt.methods) {
 			const func = new LoxFunction(
@@ -183,6 +188,10 @@ export class Interpreter {
 			methods.set(method.name.lexeme, func);
 		}
 		const klass = new LoxClass(stmt.name.lexeme, superclass, methods);
+		if (superclass) {
+			// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+			this.#environment = this.#environment.enclosing!;
+		}
 		this.#environment.assign(stmt.name, klass);
 	}
 
@@ -242,6 +251,27 @@ export class Interpreter {
 				return value;
 			}
 
+			case "super": {
+				// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+				const distance = this.#locals.get(expr)!;
+				const superclass = this.#environment.getAt(
+					distance,
+					"super",
+				) as LoxClass;
+				const object = this.#environment.getAt(
+					distance - 1,
+					"this",
+				) as LoxInstance;
+				const method = superclass.findMethod(expr.method.lexeme);
+				if (!method) {
+					throw new RuntimeError(
+						expr.method,
+						`Undefined property ${expr.method.lexeme}.`,
+					);
+				}
+				return method.bindThis(object);
+			}
+
 			case "unary":
 				const right = this.evaluate(expr.right);
 				switch (expr.operator.type) {
diff --git a/src/parser.ts b/src/parser.ts
index abf1c6e..a3923c3 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -24,9 +24,9 @@
 // unary          → ( "!" | "-" ) unary | call ;
 // call           → primary ( "(" arguments? ")" | "." IDENTIFIER )* ;
 // arguments      → expression ( "," expression )* ;
-// primary        → NUMBER | STRING | "true" | "false" | "nil"
+// primary        → NUMBER | STRING | "true" | "false" | "nil" | "this"
 //                | "(" expression ")" ;
-//                | IDENTIFIER ;
+//                | IDENTIFIER | "super" "." IDENTIFIER;
 
 import {
 	Expr,
@@ -383,6 +383,11 @@ export function parse(tokens: Token[]) {
 			return { keyword: previous(), kind: "this" };
 		} else if (match("identifier")) {
 			return { kind: "var-expr", name: previous() };
+		} else if (match("super")) {
+			const keyword = previous();
+			consume(".", "Expect '.' after 'super'.");
+			const method = consume("identifier", "Expect superclass method name.");
+			return { keyword, kind: "super", method };
 		}
 		throw error(peek(), "Expect expression.");
 	};
diff --git a/src/resolver.ts b/src/resolver.ts
index 7ebf9a7..6ffaef0 100644
--- a/src/resolver.ts
+++ b/src/resolver.ts
@@ -12,7 +12,7 @@ import { errorOnToken } from "./main.js";
 import { Token } from "./token.js";
 
 type FunctionType = "function" | "initializer" | "method" | "none";
-type ClassType = "class" | "none";
+type ClassType = "class" | "none" | "subclass";
 
 export function makeResolver(interpreter: Interpreter) {
 	const scopes: Map<string, boolean>[] = [];
@@ -100,8 +100,15 @@ export function makeResolver(interpreter: Interpreter) {
 				);
 			}
 			if (stmt.superclass) {
+				currentClass = "subclass";
 				resolveExpr(stmt.superclass);
 			}
+			if (stmt.superclass) {
+				beginScope();
+				// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+				scopes.at(-1)!.set("super", true);
+			}
+
 			beginScope();
 			// TODO: write a peek() to enforce that -1 works.
 			scopes.at(-1)?.set("this", true);
@@ -112,6 +119,9 @@ export function makeResolver(interpreter: Interpreter) {
 				);
 			}
 			endScope();
+			if (stmt.superclass) {
+				endScope();
+			}
 			currentClass = encClass;
 		},
 		expr(stmt) {
@@ -163,6 +173,17 @@ export function makeResolver(interpreter: Interpreter) {
 			resolveExpr(expr.value);
 			resolveExpr(expr.object);
 		},
+		super(expr) {
+			if (currentClass === "none") {
+				errorOnToken(expr.keyword, "Can't use 'super' outside of a class.");
+			} else if (currentClass === "class") {
+				errorOnToken(
+					expr.keyword,
+					"Can't use 'super' in a class with no superclass.",
+				);
+			}
+			resolveLocal(expr, expr.keyword);
+		},
 		this(expr) {
 			if (currentClass === "none") {
 				errorOnToken(expr.keyword, "Can't use 'this' outside of a class.");

From 82935fd39d178ac4fed907840333c92ce7e48f9b Mon Sep 17 00:00:00 2001
From: Dan Vanderkam <danvdk@gmail.com>
Date: Fri, 2 Feb 2024 17:43:12 -0500
Subject: [PATCH 3/5] new baselines

---
 baselines/chapter13/boston-creme-super.txt             | 2 ++
 baselines/chapter13/boston-creme.txt                   | 1 +
 baselines/chapter13/invalid-super-in-class.errors.txt  | 1 +
 baselines/chapter13/invalid-super-top-level.errors.txt | 1 +
 baselines/chapter13/which-super.txt                    | 1 +
 5 files changed, 6 insertions(+)
 create mode 100644 baselines/chapter13/boston-creme-super.txt
 create mode 100644 baselines/chapter13/boston-creme.txt
 create mode 100644 baselines/chapter13/invalid-super-in-class.errors.txt
 create mode 100644 baselines/chapter13/invalid-super-top-level.errors.txt
 create mode 100644 baselines/chapter13/which-super.txt

diff --git a/baselines/chapter13/boston-creme-super.txt b/baselines/chapter13/boston-creme-super.txt
new file mode 100644
index 0000000..1769cde
--- /dev/null
+++ b/baselines/chapter13/boston-creme-super.txt
@@ -0,0 +1,2 @@
+Fry until golden brown.
+Pipe full of custard and coat with chocolate.
diff --git a/baselines/chapter13/boston-creme.txt b/baselines/chapter13/boston-creme.txt
new file mode 100644
index 0000000..b2ad912
--- /dev/null
+++ b/baselines/chapter13/boston-creme.txt
@@ -0,0 +1 @@
+Fry until golden brown.
diff --git a/baselines/chapter13/invalid-super-in-class.errors.txt b/baselines/chapter13/invalid-super-in-class.errors.txt
new file mode 100644
index 0000000..5bc8cb7
--- /dev/null
+++ b/baselines/chapter13/invalid-super-in-class.errors.txt
@@ -0,0 +1 @@
+[line 3] Error at 'super': Can't use 'super' in a class with no superclass.
diff --git a/baselines/chapter13/invalid-super-top-level.errors.txt b/baselines/chapter13/invalid-super-top-level.errors.txt
new file mode 100644
index 0000000..1a00167
--- /dev/null
+++ b/baselines/chapter13/invalid-super-top-level.errors.txt
@@ -0,0 +1 @@
+[line 1] Error at 'super': Can't use 'super' outside of a class.
diff --git a/baselines/chapter13/which-super.txt b/baselines/chapter13/which-super.txt
new file mode 100644
index 0000000..5fbcdc5
--- /dev/null
+++ b/baselines/chapter13/which-super.txt
@@ -0,0 +1 @@
+A method

From 276a0a7ba234d9065fc498db5571d51d675ac9df Mon Sep 17 00:00:00 2001
From: Dan Vanderkam <danvdk@gmail.com>
Date: Fri, 2 Feb 2024 17:43:51 -0500
Subject: [PATCH 4/5] =?UTF-8?q?cr=C3=A8me=20p=C3=A2tissi=C3=A8re?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 cspell.json | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/cspell.json b/cspell.json
index 9cea18d..7e1b407 100644
--- a/cspell.json
+++ b/cspell.json
@@ -30,6 +30,8 @@
 		"quickfix",
 		"Nystrom",
 		"unshadow",
-		"klass"
+		"klass",
+		"crème",
+		"pâtissière"
 	]
 }

From cafe719c1f3f19abf744634c16dd0e5a8323581d Mon Sep 17 00:00:00 2001
From: Dan Vanderkam <danvdk@gmail.com>
Date: Fri, 2 Feb 2024 17:52:05 -0500
Subject: [PATCH 5/5] Test a few more error cases

---
 .../chapter13/inheritance-loop.errors.txt      |  2 ++
 .../chapter13/non-class-parent.errors.txt      |  2 ++
 .../non-existent-method-on-super.errors.txt    |  2 ++
 .../chapter13/non-existent-method-on-super.txt |  1 +
 .../chapter13/self-inheritance.errors.txt      |  1 +
 .../chapter13/super-without-parent.errors.txt  |  1 +
 examples/chapter13/inheritance-loop.lox        | 13 +++++++++++++
 examples/chapter13/non-class-parent.lox        |  3 +++
 .../chapter13/non-existent-method-on-super.lox | 18 ++++++++++++++++++
 examples/chapter13/self-inheritance.lox        |  1 +
 examples/chapter13/super-without-parent.lox    | 14 ++++++++++++++
 11 files changed, 58 insertions(+)
 create mode 100644 baselines/chapter13/inheritance-loop.errors.txt
 create mode 100644 baselines/chapter13/non-class-parent.errors.txt
 create mode 100644 baselines/chapter13/non-existent-method-on-super.errors.txt
 create mode 100644 baselines/chapter13/non-existent-method-on-super.txt
 create mode 100644 baselines/chapter13/self-inheritance.errors.txt
 create mode 100644 baselines/chapter13/super-without-parent.errors.txt
 create mode 100644 examples/chapter13/inheritance-loop.lox
 create mode 100644 examples/chapter13/non-class-parent.lox
 create mode 100644 examples/chapter13/non-existent-method-on-super.lox
 create mode 100644 examples/chapter13/self-inheritance.lox
 create mode 100644 examples/chapter13/super-without-parent.lox

diff --git a/baselines/chapter13/inheritance-loop.errors.txt b/baselines/chapter13/inheritance-loop.errors.txt
new file mode 100644
index 0000000..be15b6a
--- /dev/null
+++ b/baselines/chapter13/inheritance-loop.errors.txt
@@ -0,0 +1,2 @@
+Undefined variable 'B'.
+[line 1]
diff --git a/baselines/chapter13/non-class-parent.errors.txt b/baselines/chapter13/non-class-parent.errors.txt
new file mode 100644
index 0000000..8fb60e1
--- /dev/null
+++ b/baselines/chapter13/non-class-parent.errors.txt
@@ -0,0 +1,2 @@
+Superclass must be a class.
+[line 3]
diff --git a/baselines/chapter13/non-existent-method-on-super.errors.txt b/baselines/chapter13/non-existent-method-on-super.errors.txt
new file mode 100644
index 0000000..5c69ec2
--- /dev/null
+++ b/baselines/chapter13/non-existent-method-on-super.errors.txt
@@ -0,0 +1,2 @@
+Undefined property bar.
+[line 12]
diff --git a/baselines/chapter13/non-existent-method-on-super.txt b/baselines/chapter13/non-existent-method-on-super.txt
new file mode 100644
index 0000000..28153a2
--- /dev/null
+++ b/baselines/chapter13/non-existent-method-on-super.txt
@@ -0,0 +1 @@
+Parent.foo
diff --git a/baselines/chapter13/self-inheritance.errors.txt b/baselines/chapter13/self-inheritance.errors.txt
new file mode 100644
index 0000000..24b5b0e
--- /dev/null
+++ b/baselines/chapter13/self-inheritance.errors.txt
@@ -0,0 +1 @@
+[line 1] Error at 'Oops': A class can't inherit from itself.
diff --git a/baselines/chapter13/super-without-parent.errors.txt b/baselines/chapter13/super-without-parent.errors.txt
new file mode 100644
index 0000000..99c6b35
--- /dev/null
+++ b/baselines/chapter13/super-without-parent.errors.txt
@@ -0,0 +1 @@
+[line 9] Error at 'super': Can't use 'super' in a class with no superclass.
diff --git a/examples/chapter13/inheritance-loop.lox b/examples/chapter13/inheritance-loop.lox
new file mode 100644
index 0000000..9ad2ada
--- /dev/null
+++ b/examples/chapter13/inheritance-loop.lox
@@ -0,0 +1,13 @@
+class A < B {
+    foo() {
+        super.foo();
+    }
+}
+class B < A {
+    foo() {
+        super.foo();
+    }
+}
+
+var a = A();
+a.foo();
diff --git a/examples/chapter13/non-class-parent.lox b/examples/chapter13/non-class-parent.lox
new file mode 100644
index 0000000..7baae92
--- /dev/null
+++ b/examples/chapter13/non-class-parent.lox
@@ -0,0 +1,3 @@
+fun Parent() {}
+
+class Child < Parent {}
diff --git a/examples/chapter13/non-existent-method-on-super.lox b/examples/chapter13/non-existent-method-on-super.lox
new file mode 100644
index 0000000..7c102bd
--- /dev/null
+++ b/examples/chapter13/non-existent-method-on-super.lox
@@ -0,0 +1,18 @@
+class Parent {
+    foo() {
+        print "Parent.foo";
+    }
+}
+
+class Child < Parent {
+    foo() {
+        super.foo();
+    }
+    bar() {
+        super.bar();
+    }
+}
+
+var c = Child();
+c.foo();
+c.bar();
diff --git a/examples/chapter13/self-inheritance.lox b/examples/chapter13/self-inheritance.lox
new file mode 100644
index 0000000..d144a83
--- /dev/null
+++ b/examples/chapter13/self-inheritance.lox
@@ -0,0 +1 @@
+class Oops < Oops {}
diff --git a/examples/chapter13/super-without-parent.lox b/examples/chapter13/super-without-parent.lox
new file mode 100644
index 0000000..d6ec11b
--- /dev/null
+++ b/examples/chapter13/super-without-parent.lox
@@ -0,0 +1,14 @@
+class Parent {
+    foo() {
+        print "Parent.foo";
+    }
+}
+
+class Child {
+    foo() {
+        super.foo();
+    }
+}
+
+var c = Child();
+c.foo();