From c10cbcdf99824bf81fb0874deb258d5c8c7cb22d Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Mon, 6 Sep 2021 02:03:31 -0700
Subject: Chapter 18

---
 clox/src/vm.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

(limited to 'clox/src/vm.c')

diff --git a/clox/src/vm.c b/clox/src/vm.c
index 381c8c0..df9f490 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -39,6 +39,10 @@ Value pop() {
 
 static Value peek(int distance) { return vm.stackTop[-1 - distance]; }
 
+static bool isFalsey(Value value) {
+  return IS_NIL(value) || (IS_BOOL(value) && !AS_BOOL(value));
+}
+
 static InterpretResult run() {
 #define READ_BYTE() (*vm.ip++)
 #define READ_CONSTANT() (vm.chunk->constants.values[READ_BYTE()])
@@ -71,6 +75,27 @@ static InterpretResult run() {
       push(constant);
       break;
     }
+    case OP_NIL:
+      push(NIL_VAL);
+      break;
+    case OP_TRUE:
+      push(BOOL_VAL(true));
+      break;
+    case OP_FALSE:
+      push(BOOL_VAL(false));
+      break;
+    case OP_EQUAL: {
+      Value b = pop();
+      Value a = pop();
+      push(BOOL_VAL(valuesEqual(a, b)));
+      break;
+    }
+    case OP_GREATER:
+      BINARY_OP(BOOL_VAL, >);
+      break;
+    case OP_LESS:
+      BINARY_OP(BOOL_VAL, <);
+      break;
     case OP_ADD:
       BINARY_OP(NUMBER_VAL, +);
       break;
@@ -83,6 +108,9 @@ static InterpretResult run() {
     case OP_DIVIDE:
       BINARY_OP(NUMBER_VAL, /);
       break;
+    case OP_NOT:
+      push(BOOL_VAL(isFalsey(pop())));
+      break;
     case OP_NEGATE:
       if (!IS_NUMBER(peek(0))) {
         runtimeError("Operand must be a number.");
-- 
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