diff --git a/src/compiler.zig b/src/compiler.zig
index fd96032..a04fd1f 100644
--- a/src/compiler.zig
+++ b/src/compiler.zig
@@ -1,54 +1,124 @@
 const std = @import("std");
 const scanner = @import("new_scanner.zig");
 const vm = @import("vm.zig");
+const chunks = @import("chunk.zig");
+const tokens = @import("token.zig");
 
 const Allocator = std.mem.Allocator;
-const TokenType = @import("token.zig").TokenType;
+const Scanner = scanner.Scanner;
+const Chunk = chunks.Chunk;
+const Token = tokens.Token;
+const TokenType = tokens.TokenType;
+
+pub const Parser = struct {
+    previous: Token = undefined,
+    current: Token = undefined,
+
+    // TODO are those needed
+    hadError: bool = false,
+    panicMode: bool = false,
+};
 
 pub const Compiler = struct {
     src: []const u8,
     stdout: vm.StdOut,
     allocator: *Allocator,
+    parser: Parser,
+    scanr: Scanner = undefined,
+    chunk: *chunks.Chunk,
 
     pub fn init(
         allocator: *Allocator,
+        chunk: *chunks.Chunk,
         stdout: vm.StdOut,
         source: []const u8,
     ) Compiler {
         return Compiler{
             .src = source,
+            .chunk = chunk,
             .allocator = allocator,
             .stdout = stdout,
+            .parser = Parser{},
         };
     }
 
-    pub fn compile(self: *Compiler) !void {
-        var scanr = try scanner.Scanner.init(self.allocator, self.src);
-        var line: usize = 0;
+    fn errorAt(self: *Compiler, token: Token, msg: []const u8) void {
+        if (self.parser.panicMode) return;
+        self.parser.panicMode = true;
+
+        std.debug.warn("[line {}] Error", token.line);
+        if (token.ttype == TokenType.EOF) {
+            std.debug.warn(" at end");
+        } else {
+            std.debug.warn(" at '{}'", token.lexeme);
+        }
+
+        std.debug.warn(": {}\n", msg);
+        self.parser.hadError = true;
+    }
+
+    fn errorCurrent(self: *Compiler, msg: []const u8) void {
+        self.errorAt(self.parser.current, msg);
+    }
+
+    fn errorPrevious(self: *Compiler, msg: []const u8) void {
+        self.errorAt(self.parser.previous, msg);
+    }
+
+    fn advance(self: *Compiler) !void {
+        self.parser.previous = self.parser.current;
+
         while (true) {
-            var token_opt = scanr.scanToken() catch |err| {
-                std.debug.warn("Scan Error: {x}\n", err);
-                std.debug.warn(
-                    "line: {}, cur lexeme: {}\n",
-                    scanr.line,
-                    scanr.currentLexeme(),
-                );
-                break;
-            };
-
+            var token_opt = try self.scanr.scanToken();
             if (token_opt) |token| {
-                if (token.line != line) {
-                    try self.stdout.print("{} ", token.line);
-                    line = token.line;
-                } else {
-                    try self.stdout.print("  | ");
-                }
-
-                try self.stdout.print("{} '{}'\n", token.ttype, token.lexeme);
-                if (token.ttype == TokenType.EOF) break;
-            } else {
+                self.parser.current = token;
                 break;
+            } else {
+                self.errorCurrent(self.parser.current.lexeme);
             }
         }
     }
+
+    fn consume(self: *Compiler, ttype: TokenType, msg: []const u8) !void {
+        if (self.parser.current.ttype == ttype) {
+            try self.advance();
+            return;
+        }
+
+        self.errorCurrent(msg);
+    }
+
+    fn currentChunk(self: *Compiler) *chunks.Chunk {
+        return self.chunk;
+    }
+
+    fn emitByte(self: *Compiler, byte: u8) !void {
+        try self.currentChunk().write(byte, self.parser.previous.line);
+    }
+
+    fn emitBytes(self: *Compiler, byte1: u8, byte2: u82) !void {
+        try self.emitByte(byte1);
+        try self.emitByte(byte2);
+    }
+
+    fn writeReturn(self: *Compiler) !void {
+        try self.emitByte(chunks.OpCode.Return);
+    }
+
+    fn end(self: *Compiler) !void {
+        try self.writeReturn();
+    }
+
+    /// Compile the source given when initializing the compiler
+    /// into the given chunk.
+    pub fn compile(self: *Compiler, chunk: *Chunk) !bool {
+        self.scanr = try scanner.Scanner.init(self.allocator, self.src);
+
+        try self.advance();
+        //try self.expression();
+        try self.consume(.EOF, "Expect end of expression.");
+        try self.end();
+
+        return !self.parser.hadError;
+    }
 };
diff --git a/src/new_scanner.zig b/src/new_scanner.zig
index 8a1c436..2b4020d 100644
--- a/src/new_scanner.zig
+++ b/src/new_scanner.zig
@@ -230,7 +230,11 @@ pub const Scanner = struct {
     pub fn scanToken(self: *Scanner) !?Token {
         self.skipWhitespace();
         self.start = self.current;
-        if (self.isAtEnd()) return self.makeToken(TokenType.EOF);
+
+        if (self.isAtEnd()) {
+            std.debug.warn("got at end\n");
+            return self.makeToken(TokenType.EOF);
+        }
 
         var c = self.advance();
         if (isAlpha(c)) return self.doIdentifier();
diff --git a/src/vm.zig b/src/vm.zig
index 175414c..3375684 100644
--- a/src/vm.zig
+++ b/src/vm.zig
@@ -165,9 +165,16 @@ pub const VM = struct {
         //var res = try self.run();
         //self.debug("VM end\n");
         //return res;
-        var cmpr = Compiler.init(self.allocator, self.stdout, self.src);
-        try cmpr.compile();
-        return InterpretResult.Ok;
+        var chk = try Chunk.init(self.allocator);
+
+        var cmpr = Compiler.init(self.allocator, &chk, self.stdout, self.src);
+        if (!try cmpr.compile(&chk)) {
+            return InterpretResult.CompileError;
+        }
+
+        self.chk = &chk;
+        self.ip = 0;
+        return try self.run();
     }
 
     pub fn push(self: *VM, val: Value) !void {