13.1 Superclasses and Subclasses

1 files changed, 21 insertions, 13 deletions

diff --git a/src/com/craftinginterpreters/lox/Parser.java b/src/com/craftinginterpreters/lox/Parser.java
index a3f4897..3150035 100644
--- a/src/com/craftinginterpreters/lox/Parser.java
+++ b/src/com/craftinginterpreters/lox/Parser.java
@@ -3,8 +3,8 @@ package com.craftinginterpreters.lox;
 import static com.craftinginterpreters.lox.TokenType.*;
 
 import java.util.ArrayList;
-import java.util.List;
 import java.util.Arrays;
+import java.util.List;
 
 class Parser {
     private static class ParseError extends RuntimeException {
@@ -49,6 +49,13 @@ class Parser {
 
     private Stmt classDeclaration() {
         Token name = consume(IDENTIFIER, "Expect class name.");
+
+        Expr.Variable superclass = null;
+        if (match(LESS)) {
+            consume(IDENTIFIER, "Expect superclass name.");
+            superclass = new Expr.Variable(previous());
+        }
+
         consume(LEFT_BRACE, "Expect '{' before class body.");
 
         List<Stmt.Function> methods = new ArrayList<>();
@@ -58,7 +65,7 @@ class Parser {
 
         consume(RIGHT_BRACE, "Expect '}' after class body.");
 
-        return new Stmt.Class(name, methods);
+        return new Stmt.Class(name, superclass, methods);
     }
 
     private Stmt statement() {
@@ -218,7 +225,7 @@ class Parser {
                 Token name = ((Expr.Variable) expr).name;
                 return new Expr.Assign(name, value);
             } else if (expr instanceof Expr.Get) {
-                Expr.Get get = (Expr.Get)expr;
+                Expr.Get get = (Expr.Get) expr;
                 return new Expr.Set(get.object, get.name, value);
             }
 
@@ -355,7 +362,8 @@ class Parser {
             return new Expr.Literal(previous().literal);
         }
 
-        if (match(THIS)) return new Expr.This(previous());
+        if (match(THIS))
+            return new Expr.This(previous());
 
         if (match(IDENTIFIER)) {
             return new Expr.Variable(previous());
@@ -425,15 +433,15 @@ class Parser {
                 return;
 
             switch (peek().type) {
-                case CLASS:
-                case FUN:
-                case VAR:
-                case FOR:
-                case IF:
-                case WHILE:
-                case PRINT:
-                case RETURN:
-                    return;
+            case CLASS:
+            case FUN:
+            case VAR:
+            case FOR:
+            case IF:
+            case WHILE:
+            case PRINT:
+            case RETURN:
+                return;
             }
 
             advance();