From 9025da8168e505e2b0e32b89a0d94db935dace93 Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Fri, 21 Jan 2022 21:24:26 -0800
Subject: Chapter 24.1

---
 clox/src/compiler.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

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

diff --git a/clox/src/compiler.c b/clox/src/compiler.c
index beda5d5..aed21f7 100644
--- a/clox/src/compiler.c
+++ b/clox/src/compiler.c
@@ -288,6 +288,51 @@ static void expressionStatement() {
   emitByte(OP_POP);
 }
 
+static void forStatement() {
+  beginScope();
+  consume(TOKEN_LEFT_PAREN, "Expect '(' after 'for'.");
+  if (match(TOKEN_SEMICOLON)) {
+    // No initializer
+  } else if (match(TOKEN_VAR)) {
+    varDeclaration();
+  } else {
+    expressionStatement();
+  }
+
+  int loopStart = currentChunk()->count;
+  int exitJump = -1;
+  if (!match(TOKEN_SEMICOLON)) {
+    expression();
+    consume(TOKEN_SEMICOLON, "Expect ';' after loop condition.");
+
+    // Jump out of the loop if the condition is false.
+    exitJump = emitJump(OP_JUMP_IF_FALSE);
+    emitByte(OP_POP); /* Condition. */
+  }
+
+  if (!match(TOKEN_RIGHT_PAREN)) {
+    int bodyJump = emitJump(OP_JUMP);
+    int incrementStart = currentChunk()->count;
+    expression();
+    emitByte(OP_POP);
+    consume(TOKEN_RIGHT_PAREN, "Expect ')' after for clauses.");
+
+    emitLoop(loopStart);
+    loopStart = incrementStart;
+    patchJump(bodyJump);
+  }
+
+  statement();
+  emitLoop(loopStart);
+
+  if (exitJump != -1) {
+    patchJump(exitJump);
+    emitByte(OP_POP); /* Condition. */
+  }
+
+  endScope();
+}
+
 static void ifStatement() {
   consume(TOKEN_LEFT_PAREN, "Expect '(' after 'if'.");
   expression();
@@ -366,6 +411,8 @@ static void declaration() {
 static void statement() {
   if (match(TOKEN_PRINT)) {
     printStatement();
+  } else if (match(TOKEN_FOR)) {
+    forStatement();
   } else if (match(TOKEN_IF)) {
     ifStatement();
   } else if (match(TOKEN_WHILE)) {
-- 
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