From 2adc0cc33a44fde4a3de3409f03f03265dab0c1f Mon Sep 17 00:00:00 2001
From: Tom Willemse <tom@ryuslash.org>
Date: Thu, 29 Jul 2021 23:38:20 -0700
Subject: [PATCH] Chapter 15.3

---
 clox/src/chunk.h | 13 +++++++------
 clox/src/debug.c | 13 +++++++------
 clox/src/main.c  |  1 +
 clox/src/vm.c    | 11 +++++------
 4 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/clox/src/chunk.h b/clox/src/chunk.h
index 466898b..dcab3df 100644
--- a/clox/src/chunk.h
+++ b/clox/src/chunk.h
@@ -6,20 +6,21 @@
 
 typedef enum {
   OP_CONSTANT,
+  OP_NEGATE,
   OP_RETURN,
 } OpCode;
 
 typedef struct {
   int count;
   int capacity;
-  uint8_t* code;
-  int* lines;
+  uint8_t *code;
+  int *lines;
   ValueArray constants;
 } Chunk;
 
-void initChunk(Chunk* chunk);
-void freeChunk(Chunk* chunk);
-void writeChunk(Chunk* chunk, uint8_t byte, int line);
-int addConstant(Chunk* chunk, Value value);
+void initChunk(Chunk *chunk);
+void freeChunk(Chunk *chunk);
+void writeChunk(Chunk *chunk, uint8_t byte, int line);
+int addConstant(Chunk *chunk, Value value);
 
 #endif
diff --git a/clox/src/debug.c b/clox/src/debug.c
index 68fdbc5..91fe139 100644
--- a/clox/src/debug.c
+++ b/clox/src/debug.c
@@ -3,7 +3,7 @@
 #include "debug.h"
 #include "value.h"
 
-void disassembleChunk(Chunk* chunk, const char* name) {
+void disassembleChunk(Chunk *chunk, const char *name) {
   printf("== %s ==\n", name);
 
   for (int offset = 0; offset < chunk->count;) {
@@ -11,7 +11,7 @@ void disassembleChunk(Chunk* chunk, const char* name) {
   }
 }
 
-static int constantInstruction(const char* name, Chunk* chunk, int offset) {
+static int constantInstruction(const char *name, Chunk *chunk, int offset) {
   uint8_t constant = chunk->code[offset + 1];
   printf("%-16s %4d '", name, constant);
   printValue(chunk->constants.values[constant]);
@@ -19,15 +19,14 @@ static int constantInstruction(const char* name, Chunk* chunk, int offset) {
   return offset + 2;
 }
 
-static int simpleInstruction(const char* name, int offset) {
+static int simpleInstruction(const char *name, int offset) {
   printf("%s\n", name);
   return offset + 1;
 }
 
-int disassembleInstruction(Chunk* chunk, int offset) {
+int disassembleInstruction(Chunk *chunk, int offset) {
   printf("%04d ", offset);
-  if (offset > 0 &&
-      chunk->lines[offset] == chunk->lines[offset - 1]) {
+  if (offset > 0 && chunk->lines[offset] == chunk->lines[offset - 1]) {
     printf("   | ");
   } else {
     printf("%4d ", chunk->lines[offset]);
@@ -37,6 +36,8 @@ int disassembleInstruction(Chunk* chunk, int offset) {
   switch (instruction) {
   case OP_CONSTANT:
     return constantInstruction("OP_CONSTANT", chunk, offset);
+  case OP_NEGATE:
+    return simpleInstruction("OP_NEGATE", offset);
   case OP_RETURN:
     return simpleInstruction("OP_RETURN", offset);
   default:
diff --git a/clox/src/main.c b/clox/src/main.c
index 0f810ba..d2cb6bd 100644
--- a/clox/src/main.c
+++ b/clox/src/main.c
@@ -12,6 +12,7 @@ int main(int argc, const char *argv[]) {
   int constant = addConstant(&chunk, 1.2);
   writeChunk(&chunk, OP_CONSTANT, 123);
   writeChunk(&chunk, constant, 123);
+  writeChunk(&chunk, OP_NEGATE, 123);
 
   writeChunk(&chunk, OP_RETURN, 123);
 
diff --git a/clox/src/vm.c b/clox/src/vm.c
index ffd207d..e05a0c8 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -6,13 +6,9 @@
 
 VM vm;
 
-static void resetStack() {
-  vm.stackTop = vm.stack;
-}
+static void resetStack() { vm.stackTop = vm.stack; }
 
-void initVM() {
-  resetStack();
-}
+void initVM() { resetStack(); }
 
 void freeVM() {}
 
@@ -49,6 +45,9 @@ static InterpretResult run() {
       push(constant);
       break;
     }
+    case OP_NEGATE:
+      push(-pop());
+      break;
     case OP_RETURN: {
       printValue(pop());
       printf("\n");