From 4e77cfa61262a03055aeb273108fd9a49e8dfa4f Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Sat, 13 Aug 2022 00:04:31 -0700
Subject: Chapter 27.4

---
 clox/src/chunk.h    |  2 ++
 clox/src/compiler.c | 14 +++++++++++++-
 clox/src/debug.c    |  4 ++++
 clox/src/vm.c       | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/clox/src/chunk.h b/clox/src/chunk.h
index ae0ab72..9fff535 100644
--- a/clox/src/chunk.h
+++ b/clox/src/chunk.h
@@ -17,6 +17,8 @@ typedef enum {
   OP_SET_GLOBAL,
   OP_GET_UPVALUE,
   OP_SET_UPVALUE,
+  OP_GET_PROPERTY,
+  OP_SET_PROPERTY,
   OP_EQUAL,
   OP_GREATER,
   OP_LESS,
diff --git a/clox/src/compiler.c b/clox/src/compiler.c
index b21a53d..6ab4855 100644
--- a/clox/src/compiler.c
+++ b/clox/src/compiler.c
@@ -307,6 +307,18 @@ static void call(bool canAssign) {
   emitBytes(OP_CALL, argCount);
 }
 
+static void dot(bool canAssign) {
+  consume(TOKEN_IDENTIFIER, "Expect property name after '.'.");
+  uint8_t name = identifierConstant(&parser.previous);
+
+  if (canAssign && match(TOKEN_EQUAL)) {
+    expression();
+    emitBytes(OP_SET_PROPERTY, name);
+  } else {
+    emitBytes(OP_GET_PROPERTY, name);
+  }
+}
+
 static void literal(bool canAssign) {
   switch (parser.previous.type) {
   case TOKEN_FALSE:
@@ -689,7 +701,7 @@ ParseRule rules[] = {
     [TOKEN_LEFT_BRACE] = {NULL, NULL, PREC_NONE},
     [TOKEN_RIGHT_BRACE] = {NULL, NULL, PREC_NONE},
     [TOKEN_COMMA] = {NULL, NULL, PREC_NONE},
-    [TOKEN_DOT] = {NULL, NULL, PREC_NONE},
+    [TOKEN_DOT] = {NULL, dot, PREC_CALL},
     [TOKEN_MINUS] = {unary, binary, PREC_TERM},
     [TOKEN_PLUS] = {NULL, binary, PREC_TERM},
     [TOKEN_SEMICOLON] = {NULL, NULL, PREC_NONE},
diff --git a/clox/src/debug.c b/clox/src/debug.c
index a2c2c53..fe96c3d 100644
--- a/clox/src/debug.c
+++ b/clox/src/debug.c
@@ -73,6 +73,10 @@ int disassembleInstruction(Chunk *chunk, int offset) {
     return byteInstruction("OP_GET_UPVALUE", chunk, offset);
   case OP_SET_UPVALUE:
     return byteInstruction("OP_SET_UPVALUE", chunk, offset);
+  case OP_GET_PROPERTY:
+    return constantInstruction("OP_GET_PROPERTY", chunk, offset);
+  case OP_SET_PROPERTY:
+    return constantInstruction("OP_SET_PROPERTY", chunk, offset);
   case OP_EQUAL:
     return simpleInstruction("OP_EQUAL", offset);
   case OP_GREATER:
diff --git a/clox/src/vm.c b/clox/src/vm.c
index c1f0b90..1d82dd1 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -282,6 +282,38 @@ static InterpretResult run() {
       *frame->closure->upvalues[slot]->location = peek(0);
       break;
     }
+    case OP_GET_PROPERTY: {
+      if (!IS_INSTANCE(peek(0))) {
+        runtimeError("Only instances have properties.");
+        return INTERPRET_RUNTIME_ERROR;
+      }
+
+      ObjInstance *instance = AS_INSTANCE(peek(0));
+      ObjString *name = READ_STRING();
+
+      Value value;
+      if (tableGet(&instance->fields, name, &value)) {
+        pop(); /* Instance */
+        push(value);
+        break;
+      }
+
+      runtimeError("Undefined property '%s'.", name->chars);
+      return INTERPRET_RUNTIME_ERROR;
+    }
+    case OP_SET_PROPERTY: {
+      if (!IS_INSTANCE(peek(1))) {
+        runtimeError("Only instances have fields.");
+        return INTERPRET_RUNTIME_ERROR;
+      }
+
+      ObjInstance *instance = AS_INSTANCE(peek(1));
+      tableSet(&instance->fields, READ_STRING(), peek(0));
+      Value value = pop();
+      pop();
+      push(value);
+      break;
+    }
     case OP_EQUAL: {
       Value b = pop();
       Value a = pop();
-- 
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