From f4185577e56a893b9375bc94d71bef5f9eb51891 Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Fri, 12 Aug 2022 23:18:02 -0700
Subject: Chapter 27.3

---
 clox/src/memory.c | 12 ++++++++++++
 clox/src/object.c | 10 ++++++++++
 clox/src/object.h | 11 +++++++++++
 clox/src/vm.c     |  5 +++++
 4 files changed, 38 insertions(+)

diff --git a/clox/src/memory.c b/clox/src/memory.c
index 677feed..8c32386 100644
--- a/clox/src/memory.c
+++ b/clox/src/memory.c
@@ -95,6 +95,12 @@ static void blackenObject(Obj *object) {
     markArray(&function->chunk.constants);
     break;
   }
+  case OBJ_INSTANCE: {
+    ObjInstance *instance = (ObjInstance *)object;
+    markObject((Obj *)instance->klass);
+    markTable(&instance->fields);
+    break;
+  }
   case OBJ_UPVALUE:
     markValue(((ObjUpvalue *)object)->closed);
     break;
@@ -126,6 +132,12 @@ static void freeObject(Obj *object) {
     FREE(ObjFunction, object);
     break;
   }
+  case OBJ_INSTANCE: {
+    ObjInstance *instance = (ObjInstance *)object;
+    freeTable(&instance->fields);
+    FREE(ObjInstance, object);
+    break;
+  }
   case OBJ_NATIVE:
     FREE(ObjNative, object);
     break;
diff --git a/clox/src/object.c b/clox/src/object.c
index 935a258..a431314 100644
--- a/clox/src/object.c
+++ b/clox/src/object.c
@@ -53,6 +53,13 @@ ObjFunction *newFunction() {
   return function;
 }
 
+ObjInstance *newInstance(ObjClass *klass) {
+  ObjInstance *instance = ALLOCATE_OBJ(ObjInstance, OBJ_INSTANCE);
+  instance->klass = klass;
+  initTable(&instance->fields);
+  return instance;
+}
+
 ObjNative *newNative(NativeFn function) {
   ObjNative *native = ALLOCATE_OBJ(ObjNative, OBJ_NATIVE);
   native->function = function;
@@ -131,6 +138,9 @@ void printObject(Value value) {
   case OBJ_FUNCTION:
     printFunction(AS_FUNCTION(value));
     break;
+  case OBJ_INSTANCE:
+    printf("%s instance", AS_INSTANCE(value)->klass->name->chars);
+    break;
   case OBJ_NATIVE:
     printf("<native fn>");
     break;
diff --git a/clox/src/object.h b/clox/src/object.h
index 44de6ed..1cef631 100644
--- a/clox/src/object.h
+++ b/clox/src/object.h
@@ -3,6 +3,7 @@
 
 #include "chunk.h"
 #include "common.h"
+#include "table.h"
 #include "value.h"
 
 #define OBJ_TYPE(value) (AS_OBJ(value)->type)
@@ -10,12 +11,14 @@
 #define IS_CLASS(value) isObjType(value, OBJ_CLASS)
 #define IS_CLOSURE(value) isObjType(value, OBJ_CLOSURE)
 #define IS_FUNCTION(value) isObjType(value, OBJ_FUNCTION)
+#define IS_INSTANCE(value) isObjType(value, OBJ_INSTANCE)
 #define IS_NATIVE(value) isObjType(value, OBJ_NATIVE)
 #define IS_STRING(value) isObjType(value, OBJ_STRING)
 
 #define AS_CLASS(value) ((ObjClass *)AS_OBJ(value))
 #define AS_CLOSURE(value) ((ObjClosure *)AS_OBJ(value))
 #define AS_FUNCTION(value) ((ObjFunction *)AS_OBJ(value))
+#define AS_INSTANCE(value) ((ObjInstance *)AS_OBJ(value))
 #define AS_NATIVE(value) (((ObjNative *)AS_OBJ(value))->function)
 #define AS_STRING(value) ((ObjString *)AS_OBJ(value))
 #define AS_CSTRING(value) (((ObjString *)AS_OBJ(value))->chars)
@@ -24,6 +27,7 @@ typedef enum {
   OBJ_CLASS,
   OBJ_CLOSURE,
   OBJ_FUNCTION,
+  OBJ_INSTANCE,
   OBJ_NATIVE,
   OBJ_STRING,
   OBJ_UPVALUE,
@@ -76,9 +80,16 @@ typedef struct {
   ObjString *name;
 } ObjClass;
 
+typedef struct {
+  Obj obj;
+  ObjClass *klass;
+  Table fields;
+} ObjInstance;
+
 ObjClass *newClass(ObjString *name);
 ObjClosure *newClosure(ObjFunction *function);
 ObjFunction *newFunction();
+ObjInstance *newInstance(ObjClass *klass);
 ObjNative *newNative(NativeFn function);
 ObjString *takeString(char *chars, int length);
 ObjString *copyString(const char *chars, int length);
diff --git a/clox/src/vm.c b/clox/src/vm.c
index eab8c47..c1f0b90 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -108,6 +108,11 @@ static bool call(ObjClosure *closure, int argCount) {
 static bool callValue(Value callee, int argCount) {
   if (IS_OBJ(callee)) {
     switch (OBJ_TYPE(callee)) {
+    case OBJ_CLASS: {
+      ObjClass *klass = AS_CLASS(callee);
+      vm.stackTop[-argCount - 1] = OBJ_VAL(newInstance(klass));
+      return true;
+    }
     case OBJ_CLOSURE:
       return call(AS_CLOSURE(callee), argCount);
     case OBJ_NATIVE: {
-- 
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