From 44e47b89de9e7d9f7d86e1f7d532b70c952a8ab3 Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Sun, 13 Mar 2022 19:41:34 -0700
Subject: Chapter 24.4

---
 clox/src/compiler.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 48 insertions(+), 6 deletions(-)

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

diff --git a/clox/src/compiler.c b/clox/src/compiler.c
index 44eede8..bd835f2 100644
--- a/clox/src/compiler.c
+++ b/clox/src/compiler.c
@@ -46,7 +46,8 @@ typedef struct {
 
 typedef enum { TYPE_FUNCTION, TYPE_SCRIPT } FunctionType;
 
-typedef struct {
+typedef struct Compiler {
+  struct Compiler *enclosing;
   ObjFunction *function;
   FunctionType type;
 
@@ -171,12 +172,17 @@ static void patchJump(int offset) {
 }
 
 static void initCompiler(Compiler *compiler, FunctionType type) {
+  compiler->enclosing = current;
   compiler->function = NULL;
   compiler->type = type;
   compiler->localCount = 0;
   compiler->scopeDepth = 0;
   compiler->function = newFunction();
   current = compiler;
+  if (type != TYPE_SCRIPT) {
+    current->function->name =
+        copyString(parser.previous.start, parser.previous.length);
+  }
 
   Local *local = &current->locals[current->localCount++];
   local->depth = 0;
@@ -196,6 +202,7 @@ static ObjFunction *endCompiler() {
   }
 #endif
 
+  current = current->enclosing;
   return function;
 }
 
@@ -288,6 +295,43 @@ static void block() {
   consume(TOKEN_RIGHT_BRACE, "Expect '}' after block.");
 }
 
+static void function(FunctionType type) {
+  Compiler compiler;
+  initCompiler(&compiler, type);
+  beginScope();
+
+  consume(TOKEN_LEFT_PAREN, "Expect '(' after function name.");
+  if (!check(TOKEN_RIGHT_PAREN)) {
+    do {
+      current->function->arity++;
+      if (current->function->arity > 255) {
+        errorAtCurrent("Can't have more than 250 parameters.");
+      }
+      uint8_t constant = parseVariable("Expect parameter name.");
+      defineVariable(constant);
+    } while (match(TOKEN_COMMA));
+  }
+  consume(TOKEN_RIGHT_PAREN, "Expect ')' after parameters.");
+  consume(TOKEN_LEFT_BRACE, "Expect '{' before function body.");
+  block();
+
+  ObjFunction *function = endCompiler();
+  emitBytes(OP_CONSTANT, makeConstant(OBJ_VAL(function)));
+}
+
+static void markInitialized() {
+  if (current->scopeDepth == 0)
+    return;
+  current->locals[current->localCount - 1].depth = current->scopeDepth;
+}
+
+static void funDeclaration() {
+  uint8_t global = parseVariable("Expect function name.");
+  markInitialized();
+  function(TYPE_FUNCTION);
+  defineVariable(global);
+}
+
 static void varDeclaration() {
   uint8_t global = parseVariable("Expect variable name.");
 
@@ -417,7 +461,9 @@ static void synchronize() {
 }
 
 static void declaration() {
-  if (match(TOKEN_VAR)) {
+  if (match(TOKEN_FUN)) {
+    funDeclaration();
+  } else if (match(TOKEN_VAR)) {
     varDeclaration();
   } else {
     statement();
@@ -653,10 +699,6 @@ static uint8_t parseVariable(const char *errorMessage) {
   return identifierConstant(&parser.previous);
 }
 
-static void markInitialized() {
-  current->locals[current->localCount - 1].depth = current->scopeDepth;
-}
-
 static void defineVariable(uint8_t global) {
   if (current->scopeDepth > 0) {
     markInitialized();
-- 
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