Chapter 15.3

clox/src/chunk.h

@@ -6,6 +6,7 @@
 
 typedef enum {
   OP_CONSTANT,
+  OP_NEGATE,
   OP_RETURN,
 } OpCode;
 

clox/src/debug.c

@@ -26,8 +26,7 @@ static int simpleInstruction(const char* name, int offset) {
 
 int disassembleInstruction(Chunk *chunk, int offset) {
   printf("%04d ", offset);
-  if (offset > 0 &&
+  if (offset > 0 && chunk->lines[offset] == chunk->lines[offset - 1]) {
-      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:

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);
 

clox/src/vm.c

@@ -6,13 +6,9 @@
 
 VM vm;
 
-static void resetStack() {
+static void resetStack() { vm.stackTop = vm.stack; }
-  vm.stackTop = vm.stack;
-}
 
-void initVM() {
+void initVM() { resetStack(); }
-  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");