diff --git a/.gitignore b/.gitignore
index a8ba56d..5a66296 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,4 +16,5 @@ lox-test-*
 *.lst
 
 .msc/
+test/test.lox
 
diff --git a/dub.sdl b/dub.sdl
index 58a534e..90eb9b4 100644
--- a/dub.sdl
+++ b/dub.sdl
@@ -4,13 +4,19 @@ authors "tanya"
 copyright "Copyright © 2025, tanya"
 license "MPL-2.0"
 dependency "commandr" version="~>1.1.0"
-dependency "taggedalgebraic" version="~>0.11.23"
+dependency "colored" version="~>0.0.33"
 targetType "executable"
-buildRequirements "requireBoundsCheck" "requireContracts"
-
-versions "LoxConcatNonStrings" "LoxExtraNativeFuncs"
-
-configuration "jlox" {
-	sourcePaths "src/jlox" "src/common"
+sourcePaths
+configuration "clox" {
+	/* debugVersions "traceExec" */
+	debugVersions "printCode"
+	targetType "executable"
+	sourcePaths "src/clox" "src/common"
+	buildRequirements "requireBoundsCheck" "requireContracts"
+}
+configuration "jlox" {
+	targetType "executable"
+	sourcePaths "src/jlox" "src/common"
+	versions "LoxConcatNonStrings" "LoxExtraNativeFuncs" "LoxPrintMultiple"
+	buildRequirements "requireBoundsCheck" "requireContracts"
 }
-
diff --git a/dub.selections.json b/dub.selections.json
index 6b90314..ead0009 100644
--- a/dub.selections.json
+++ b/dub.selections.json
@@ -1,7 +1,9 @@
 {
 	"fileVersion": 1,
 	"versions": {
+		"colored": "0.0.33",
 		"commandr": "1.1.0",
-		"taggedalgebraic": "0.11.23"
+		"taggedalgebraic": "0.11.23",
+		"unit-threaded": "2.2.3"
 	}
 }
diff --git a/src/clox/chunk.d b/src/clox/chunk.d
new file mode 100644
index 0000000..e41bcaf
--- /dev/null
+++ b/src/clox/chunk.d
@@ -0,0 +1,69 @@
+module clox.chunk;
+
+import std.container.array;
+import std.stdio;
+import std.algorithm.searching;
+
+import clox.value;
+import clox.container.rle;
+import clox.container.int24;
+
+enum SimpleOp;
+enum LogicOp;
+enum ValueOp;
+enum ArithOp;
+enum CompOp;
+enum OpCode : ubyte{
+	Constant,
+	@ValueOp Nil,
+	@ValueOp True,
+	@ValueOp False,
+
+	@(SimpleOp, CompOp) Equal,
+	@(SimpleOp, CompOp) Greater,
+	@(SimpleOp, CompOp) Less,
+	@(SimpleOp, CompOp) NotEqual,
+	@(SimpleOp, CompOp) GreaterEqual,
+	@(SimpleOp, CompOp) LessEqual,
+
+	@(SimpleOp, ArithOp) Add,
+	@(SimpleOp, ArithOp) Subtract,
+	@(SimpleOp, ArithOp) Multiply,
+	@(SimpleOp, ArithOp) Divide,
+
+	@(SimpleOp, LogicOp) Not,
+	@(SimpleOp, LogicOp) Negate,
+	@(SimpleOp) Return,
+}
+import std.traits: hasUDA;
+bool isSimpleOp(alias op)() => hasUDA!(op, SimpleOp);
+bool isValueOp(alias op)() => hasUDA!(op, ValueOp);
+bool isLogicOp(alias op)() => hasUDA!(op, LogicOp);
+bool isCompOp(alias op)() => hasUDA!(op, CompOp);
+bool isArithOp(alias op)() => hasUDA!(op, ArithOp);
+bool isSize1Op(alias op)() => isSimpleOp!op || isValueOp!op;
+static assert( isSimpleOp!(OpCode.Equal) );
+static assert( !isSimpleOp!(OpCode.Constant) );
+
+struct Chunk{
+	Array!ubyte code;
+	Rle!(Uint24, ubyte) lines;
+	Array!Value constants;
+	uint addConstant(in Value value) @nogc nothrow {
+		long index = constants[].countUntil(value);
+		if(index >= 0)
+			return cast(uint)index;
+		constants ~= value;
+		return cast(uint)((constants.length) - 1);
+	}
+	void write(ubyte b, uint line = 0) @nogc nothrow {
+		ubyte[1] data = [ b ];
+		write(data, line);
+	}
+	void write(ubyte[] b, uint line = 0) @nogc nothrow {
+		code ~= b;
+		foreach(i; 0 .. b.length)
+			lines ~= Uint24(line); // TODO could be done without a loop
+	}
+}
+
diff --git a/src/clox/compiler.d b/src/clox/compiler.d
new file mode 100644
index 0000000..1107ca5
--- /dev/null
+++ b/src/clox/compiler.d
@@ -0,0 +1,30 @@
+module clox.compiler;
+
+import std.stdio;
+
+import clox.scanner, clox.parser, clox.emitter;
+import clox.chunk;
+import clox.value;
+import clox.util;
+import clox.parserules;
+import clox.dbg;
+
+struct Compiler{
+	Scanner scanner;
+	Parser parser;
+	Emitter emitter;
+	bool compile(string source, Chunk* chunk){
+		scanner = Scanner(source);
+		parser = Parser(&this);
+		emitter = Emitter(&this, chunk);
+
+		parser.advance();
+		parser.expression();
+		parser.consume(Token.Type.EOF, "Expect end of expression.");
+		debug writeln(*chunk);
+		emitter.endCompiler();
+		return !parser.hadError;
+	}
+}
+
+
diff --git a/src/clox/container/int24.d b/src/clox/container/int24.d
new file mode 100644
index 0000000..406a933
--- /dev/null
+++ b/src/clox/container/int24.d
@@ -0,0 +1,26 @@
+module clox.container.int24;
+
+struct Uint24{
+	nothrow: @nogc: @safe:
+	ubyte[3] data;
+	static Uint24 opCall(uint n){
+		import std.bitmanip : nativeToLittleEndian;
+		Uint24 u3;
+		assert(n <= 16_777_215);
+		ubyte[uint.sizeof] d = nativeToLittleEndian!uint(n);
+		u3.data[0 .. 3] = d[0 .. 3];
+		return u3;
+	}
+}
+uint toUint(Uint24 u3) @nogc nothrow @safe {
+	import std.bitmanip : littleEndianToNative;
+	ubyte[4] temp;
+	temp[0 .. 3] = u3.data;
+	return littleEndianToNative!uint(temp);
+}
+unittest{
+	static assert(Uint24.sizeof == 3);
+	assert(Uint24(5).toUint == 5);
+	assert(Uint24(16_777_215).toUint == 16_777_215);
+}
+
diff --git a/src/clox/container/rle.d b/src/clox/container/rle.d
new file mode 100644
index 0000000..f6e117a
--- /dev/null
+++ b/src/clox/container/rle.d
@@ -0,0 +1,62 @@
+module clox.container.rle;
+
+import std.traits;
+import std.container.array;
+
+struct Rle(T, L = ubyte) if(isUnsigned!L){
+	nothrow: @nogc:
+	align(1) struct Count{
+		T item;
+		L num;
+	}
+	size_t total;
+	Array!Count data;
+	private void pushNew(T item){
+		data ~= Count(item, 0);
+	}
+	size_t push(T item){
+		if(data.length){
+			Count* d = &data[(data.length)-1];
+			if(d.item == item && d.num < L.max){
+				d.num++;
+				return total++;
+			}
+		}
+		pushNew(item);
+		return total++;
+	}
+	T opOpAssign(string op: "~")(T rhs){
+		push(rhs);
+		return rhs;
+	}
+	T opIndex(size_t n) const @safe{
+		assert(n < total);
+		size_t c;
+		for(size_t i; i < n;){
+			i += data[c].num + 1;
+			if(i <= n)
+				c++;
+		}
+		return data[c].item;
+	}
+}
+unittest{
+	import clox.container.int24;
+	auto rl = Rle!(Uint24, ubyte)();
+	static assert(rl.Count.sizeof == 4);
+	foreach(i; 0..300){
+		size_t index = rl.push(Uint24(5));
+		assert(rl[index].toUint == 5);
+	}
+	assert(rl[299].toUint == 5);
+	foreach(i; 0..30){
+		size_t index = rl.push(Uint24(0));
+		assert(rl[index].toUint == 0);
+	}
+	assert(rl[0].toUint == 5);
+	foreach(i; 0..300){
+		size_t index = rl.push(Uint24(16_777_215));
+		assert(rl[index].toUint == 16_777_215);
+	}
+}
+
diff --git a/src/clox/container/stack.d b/src/clox/container/stack.d
new file mode 100644
index 0000000..9dabed1
--- /dev/null
+++ b/src/clox/container/stack.d
@@ -0,0 +1,26 @@
+module clox.container.stack;
+
+struct Stack(T, size_t N){
+	@nogc: nothrow:
+	T* top;
+	T[N] data;
+	invariant{ assert(top <= data.ptr + N); assert(top >= data.ptr); }
+	this(int _) @safe{
+		top = data.ptr;
+	}
+	void push(T value){
+		assert(top < data.ptr + N);
+		debug assert(*top is T.init);
+		*(top++) = value;
+	}
+	T pop(){
+		assert(top > data.ptr);
+		T t = *(--top);
+		debug *(top) = T.init;
+		return t;
+	}
+	const(T)[] live() const @safe{
+		return data[0 .. (top - data.ptr)];
+	}
+}
+
diff --git a/src/clox/container/varint.d b/src/clox/container/varint.d
new file mode 100644
index 0000000..d1d467b
--- /dev/null
+++ b/src/clox/container/varint.d
@@ -0,0 +1,73 @@
+module clox.container.varint;
+
+struct VarUint{
+	import std.bitmanip;
+	nothrow: @nogc:
+	uint i;
+	ubyte len;
+	ubyte[4] data;
+	this(long l) @safe {
+		if(l < 0b1000_0000){
+			len = 1;
+			data[0] = (cast(ubyte)l);
+			return;
+		}
+		if(l < 0b0100_0000__0000_0000){
+			len = 2;
+			data[0 .. 2] = nativeToBigEndian(cast(ushort)l);
+			data[0] |= 0b1000_0000;
+			return;
+		}
+		if(l < 0b0010_0000__0000_0000__0000_0000__0000_0000){
+			len = 4;
+			data[0 .. 4] = nativeToBigEndian(cast(uint)l);
+			data[0] |= 0b1100_0000;
+			return;
+		}
+		assert(0);
+	}
+	static VarUint read(const(ubyte)[] data) @safe {
+		VarUint v;
+		ubyte a = data[0];
+		if((data[0] & 0b1000_0000) == 0){
+			v.i = a;
+			v.len = 1;
+			return v;
+		}
+		if((a & 0b0100_0000) == 0){
+			ubyte[2] d = data[0 .. 2];
+			d[0] &= 0b0111_1111;
+			v.i = bigEndianToNative!ushort(d);
+			v.len = 2;
+			return v;
+		}
+		if((a & 0b0010_0000) == 0){
+			ubyte[4] d = data[0 .. 4];
+			d[0] &= 0b0011_1111;
+			v.i = bigEndianToNative!uint(d);
+			v.len = 4;
+			return v;
+		}
+		assert(0);
+	}
+	ubyte[] bytes() @nogc nothrow {
+		return data[0 .. len];
+	}
+}
+unittest{
+	import std.range;
+	assert(VarUint(5).bytes.length == 1);
+	assert(VarUint(127).bytes.length == 1);
+	assert(VarUint(128).bytes.length == 2);
+	assert(VarUint(536_870_911).bytes.length == 4);
+	foreach(ulong i; [
+		0, 1, 2, 5,
+		150, 127, 128,
+		536_870_911,
+		ushort.max * 100
+	]){
+		auto vi = VarUint(i);
+		assert(i == VarUint.read(vi.bytes).i);
+	}
+}
+
diff --git a/src/clox/container/vartype.d b/src/clox/container/vartype.d
new file mode 100644
index 0000000..1a27cc9
--- /dev/null
+++ b/src/clox/container/vartype.d
@@ -0,0 +1,59 @@
+module clox.container.vartype;
+
+import std.stdio;
+import std.algorithm;
+import std.array;
+import std.uni;
+import std.conv;
+
+struct VarType(S) if(is(S == union)){
+	private enum members = __traits(derivedMembers, S);
+	mixin("enum Type{ None, ", [members].map!asCapitalized.join(", "), "}");
+	private S value;
+	private Type _type;
+	Type type() const @safe @nogc nothrow => _type;
+	private void check(Type t) const @safe nothrow @nogc{
+		assert(this.type == t, "Tried to get wrong type");
+	}
+	private template funcs(string G, string T){
+		mixin("bool is", G, "() const nothrow @nogc @safe => this.type == this.Type.", G, ";");
+		mixin("auto get", G, "() const nothrow @nogc { check(this.Type.", G, "); return value.", T, "; }");
+		mixin("void set", G, "(typeof(S.", T, ") v = typeof(S.", T, ").init){ this._type = this.Type.", G, "; this.value.", T, " = v; }");
+		mixin("static auto ", T, "(typeof(S.", T, ") v){ typeof(this) vt; vt.set", G, "(v); return vt; }");
+		mixin("static auto ", T, "(){ typeof(this) vt; vt.set", G, "(); return vt; }");
+	}
+	static foreach(s; members){
+		mixin funcs!(s.asCapitalized.to!string, s);
+	}
+	string toString() const{
+		final switch(_type){
+			static foreach(s; members){
+				mixin("case Type.", s.asCapitalized.to!string, ": return _type.to!string ~ ':' ~ get", s.asCapitalized.to!string, ".to!string ;");
+			}
+			case Type.None: return "None";
+		}
+	}
+}
+
+unittest{
+	import std.exception, std.stdio;
+	union Test{
+		uint u;
+		int i;
+		double d;
+	}
+	auto i = VarType!Test.i(-5);
+	assert(i.getI == -5);
+	assert(i.type == i.Type.I);
+	assert(i.isI);
+	assert(!i.isD);
+	i.setD(0.5);
+	assert(i.getD == 0.5);
+	assert(i.type == i.Type.D);
+	assert(i.isD);
+	assert(!i.isU);
+
+	auto i2 = VarType!Test.i();
+	assert(i2.isI);
+}
+
diff --git a/src/clox/dbg.d b/src/clox/dbg.d
new file mode 100644
index 0000000..570efc5
--- /dev/null
+++ b/src/clox/dbg.d
@@ -0,0 +1,66 @@
+module clox.dbg;
+
+import std.stdio;
+import std.conv;
+import std.uni;
+import std.format;
+
+import colored;
+
+import clox.chunk;
+import clox.value;
+import clox.util;
+import clox.container.varint;
+import clox.container.int24;
+
+private ulong simpleInstruction(alias op)(string name, ulong offset){
+	static if(isValueOp!op)
+		writeln(name.cyan);
+	else static if(isLogicOp!op)
+		writeln(name.lightRed);
+	else static if(isCompOp!op)
+		writeln(name.red);
+	else static if(isArithOp!op)
+		writeln(name.yellow);
+	else
+		writeln(name.lightCyan);
+	return offset + 1;
+}
+private ulong constantInstruction(string name, Chunk* chunk, ulong offset){
+	/* ubyte constant = chunk.code[offset + 1]; */
+	VarUint constant = VarUint.read(chunk.code.data[offset + 1 .. $]);
+	/* writeln(constant); */
+	write("%-16s".format(name).cyan, " %4d ".format(constant.i).lightMagenta, "'");
+	printValue(chunk.constants[constant.i]);
+	writeln("'");
+	return offset + 1 + constant.len;
+}
+
+void disassembleChunk(Chunk* chunk, string name = "chunk"){
+	writefln("== %s ==", name);
+	for(ulong offset = 0; offset < chunk.code.length;)
+		offset = disassembleInstruction(chunk, offset);
+}
+ulong disassembleInstruction(Chunk* chunk, const ulong offset){
+	write(" %04d ".format(offset).lightGray);
+	if(offset > 0 && chunk.lines[offset] == chunk.lines[offset - 1]){
+		write("    | ".darkGray);
+	} else {
+		write(" %4d ".format(chunk.lines[offset].toUint).lightGray);
+	}
+	ubyte instruction = chunk.code[offset];
+	with(OpCode) switch(instruction){
+		import std.meta, std.traits;
+		case Constant:
+			return constantInstruction("OP_CONSTANT", chunk, offset);
+		static foreach(k; Filter!(isSize1Op, EnumMembers!OpCode)){
+			case k:
+				static name = "OP_" ~ (k.to!string).toUpper;
+				return simpleInstruction!k(name, offset);
+		}
+		default:
+			writefln("Unknown opcode %d", instruction);
+			return offset + 1;
+	}
+}
+
diff --git a/src/clox/emitter.d b/src/clox/emitter.d
new file mode 100644
index 0000000..116f504
--- /dev/null
+++ b/src/clox/emitter.d
@@ -0,0 +1,51 @@
+module clox.emitter;
+
+import clox.compiler;
+import clox.chunk;
+import clox.value;
+import clox.util;
+import clox.dbg;
+
+import clox.container.varint;
+
+struct Emitter{
+	Compiler* compiler;
+	Chunk* chunk;
+	private uint line = 1;
+	Chunk* currentChunk(){
+		return chunk;
+	}
+	void emit(Args...)(Args args){
+		static foreach(v; args){{
+			static if(is(typeof(v) == OpCode)){
+				auto bytes = v;
+			} else static if(is(typeof(v) == uint)){
+				auto bytes = VarUint(v).bytes;
+			} else {
+				static assert(0);
+			}
+			currentChunk.write(bytes, line);
+		}}
+	}
+	void emitConstant(Value value){
+		emit(OpCode.Constant, makeConstant(value));
+	}
+	void emitReturn(){
+		emit(OpCode.Return);
+	}
+	void endCompiler(){
+		emitReturn();
+		debug(printCode){
+			if(!compiler.parser.hadError)
+				disassembleChunk(currentChunk());
+		}
+	}
+	uint makeConstant(Value value){
+		uint constant = chunk.addConstant(value);
+		return constant;
+	}
+	void setLine(uint l){
+		this.line = l;
+	}
+}
+
diff --git a/src/clox/main.d b/src/clox/main.d
new file mode 100644
index 0000000..19e0fe7
--- /dev/null
+++ b/src/clox/main.d
@@ -0,0 +1,46 @@
+module clox.main;
+
+import std.stdio;
+import std.file;
+
+import clox.chunk;
+import clox.dbg;
+import clox.vm;
+
+extern(C) int isatty(int);
+
+struct Lox{
+	VM vm;
+	this(int _){
+		vm = VM(0);
+	}
+	int runFile(string path){
+		string source = path.readText();
+		VM.InterpretResult result = vm.interpret(source);
+		final switch(result){
+			case VM.InterpretResult.CompileError: return 65;
+			case VM.InterpretResult.RuntimeError: return 70;
+			case VM.InterpretResult.Ok: return 0;
+		}
+	}
+	int runPrompt(){
+		while(true){
+			write("lox> ");
+			string line = stdin.readln();
+			if(!line){
+				writeln();
+				return 0;
+			}
+			vm.interpret(line);
+		}
+	}
+}
+
+int main(string[] argv){
+	Lox lox = Lox(0);
+	if(isatty(stdin.fileno))
+		return lox.runPrompt();
+	else
+		return lox.runFile("/dev/stdin");
+}
+
diff --git a/src/clox/parser.d b/src/clox/parser.d
new file mode 100644
index 0000000..24bbdbd
--- /dev/null
+++ b/src/clox/parser.d
@@ -0,0 +1,66 @@
+module clox.parser;
+
+import clox.compiler;
+import clox.value;
+import clox.scanner;
+import clox.parserules;
+
+struct Parser{
+	Compiler* compiler;
+	Token current, previous;
+	bool hadError, panicMode;
+	void errorAtCurrent(string message){
+		errorAt(current, message);
+	}
+	void error(string message){
+		errorAt(previous, message);
+	}
+	void errorAt(in ref Token token, string message){
+		import core.stdc.stdio;
+		if(panicMode)
+			return;
+		panicMode = true;
+		fprintf(stderr, "[line %d] Error", token.line);
+		if(token.type == Token.Type.EOF){
+			fprintf(stderr, " at end");
+		} else if(token.type != Token.Type.Error){
+			fprintf(stderr, " at '%.*s'", cast(int)token.lexeme.length, token.lexeme.ptr);
+		}
+		fprintf(stderr, ": %.*s\n", cast(int)message.length, message.ptr);
+		hadError = true;
+	}
+	auto consume(Token.Type type, string msg){
+		if(current.type == type){
+			advance();
+			return;
+		}
+		errorAtCurrent(msg);
+	}
+	void advance(){
+		previous = current;
+		while(true){
+			current = compiler.scanner.scan();
+			if(current.type != Token.Type.Error)
+				break;
+			errorAtCurrent(current.lexeme);
+		}
+	}
+
+	void expression(){
+		parsePrecedence(Precedence.Assignment);
+	}
+	void parsePrecedence(Precedence precedence){
+		advance();
+		ParseFn prefixRule = ParseRule.get(previous.type).prefix;
+		if(prefixRule == null){
+			error("Expect expression.");
+			return;
+		}
+		prefixRule(compiler);
+		while(precedence <= ParseRule.get(current.type).precedence){
+			advance();
+			ParseFn infixRule = ParseRule.get(previous.type).infix;
+			infixRule(compiler);
+		}
+	}
+}
diff --git a/src/clox/parserules.d b/src/clox/parserules.d
new file mode 100644
index 0000000..a8bff9e
--- /dev/null
+++ b/src/clox/parserules.d
@@ -0,0 +1,128 @@
+module clox.parserules;
+
+import clox.compiler;
+import clox.chunk;
+import clox.scanner;
+import clox.value;
+
+alias ParseFn = void function(Compiler* compiler);
+
+private void number(Compiler* compiler){
+	import core.stdc.stdlib : strtod;
+	Token token = compiler.parser.previous;
+	double value = strtod(token.lexeme.ptr, null);
+	compiler.emitter.setLine(token.line);
+	compiler.emitter.emitConstant(Value.num(value));
+}
+private void grouping(Compiler* compiler){
+	compiler.parser.expression();
+	compiler.parser.consume(Token.Type.RightParen, "Expect ')' after expression.");
+}
+private void unary(Compiler* compiler){
+	Token operator = compiler.parser.previous;
+	compiler.parser.parsePrecedence(Precedence.Unary);
+	compiler.emitter.setLine(operator.line);
+	switch(operator.type){
+		case Token.Type.Minus: compiler.emitter.emit(OpCode.Negate); break;
+		case Token.Type.Bang: compiler.emitter.emit(OpCode.Not); break;
+		default: assert(0);
+	}
+}
+private void binary(Compiler* compiler){
+	Token operator = compiler.parser.previous;
+	immutable(ParseRule)* rule = ParseRule.get(operator.type);
+	compiler.parser.parsePrecedence(cast(Precedence)(rule.precedence + 1));
+	compiler.emitter.setLine(operator.line);
+	switch(operator.type){
+		case Token.Type.Plus:  compiler.emitter.emit(OpCode.Add); break;
+		case Token.Type.Minus: compiler.emitter.emit(OpCode.Subtract); break;
+		case Token.Type.Star:  compiler.emitter.emit(OpCode.Multiply); break;
+		case Token.Type.Slash: compiler.emitter.emit(OpCode.Divide); break;
+
+		case Token.Type.BangEqual:  compiler.emitter.emit(OpCode.NotEqual); break;
+		case Token.Type.EqualEqual: compiler.emitter.emit(OpCode.Equal); break;
+
+		case Token.Type.Greater:  compiler.emitter.emit(OpCode.Greater); break;
+		case Token.Type.GreaterEqual: compiler.emitter.emit(OpCode.GreaterEqual); break;
+
+		case Token.Type.Less: compiler.emitter.emit(OpCode.Less); break;
+		case Token.Type.LessEqual: compiler.emitter.emit(OpCode.LessEqual); break;
+
+		default: assert(0);
+	}
+}
+private void literal(Compiler* compiler){
+	switch(compiler.parser.previous.type){
+		case Token.Type.True: compiler.emitter.emit(OpCode.True); break;
+		case Token.Type.False: compiler.emitter.emit(OpCode.False); break;
+		case Token.Type.Nil: compiler.emitter.emit(OpCode.Nil); break;
+		default: assert(0);
+	}
+}
+
+struct ParseRule{
+	ParseFn prefix;
+	ParseFn infix;
+	Precedence precedence;
+	static immutable(ParseRule)* get(Token.Type type) @nogc nothrow{
+		return &rules[type];
+	}
+}
+
+enum Precedence{
+	None,
+	Assignment,  // =
+	Or,          // or
+	And,         // and
+	Equality,    // == !=
+	Comparison,  // < > <= >=
+	Term,        // + -
+	Factor,      // * /
+	Unary,       // ! -
+	Call,        // . ()
+	Primary
+}
+
+immutable ParseRule[Token.Type.max+1] rules = [
+	Token.Type.LeftParen     : ParseRule(&grouping, null,    Precedence.None),
+	Token.Type.RightParen    : ParseRule(null,      null,    Precedence.None),
+	Token.Type.LeftBrace     : ParseRule(null,      null,    Precedence.None),
+	Token.Type.RightBrace    : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Comma         : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Dot           : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Minus         : ParseRule(&unary,    &binary, Precedence.Term),
+	Token.Type.Plus          : ParseRule(null,      &binary, Precedence.Term),
+	Token.Type.Semicolon     : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Slash         : ParseRule(null,      &binary, Precedence.Factor),
+	Token.Type.Star          : ParseRule(null,      &binary, Precedence.Factor),
+	Token.Type.Bang          : ParseRule(&unary,    null,    Precedence.None),
+	Token.Type.BangEqual     : ParseRule(null,      &binary, Precedence.Equality),
+	Token.Type.Equal         : ParseRule(null,      null,    Precedence.None),
+	Token.Type.EqualEqual    : ParseRule(null,      &binary, Precedence.Equality),
+	Token.Type.Greater       : ParseRule(null,      &binary, Precedence.Comparison),
+	Token.Type.GreaterEqual  : ParseRule(null,      &binary, Precedence.Comparison),
+	Token.Type.Less          : ParseRule(null,      &binary, Precedence.Comparison),
+	Token.Type.LessEqual     : ParseRule(null,      &binary, Precedence.Comparison),
+	Token.Type.Identifier    : ParseRule(null,      null,    Precedence.None),
+	Token.Type.String        : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Number        : ParseRule(&number,   null,    Precedence.None),
+	Token.Type.And           : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Class         : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Else          : ParseRule(null,      null,    Precedence.None),
+	Token.Type.False         : ParseRule(&literal,  null,    Precedence.None),
+	Token.Type.For           : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Fun           : ParseRule(null,      null,    Precedence.None),
+	Token.Type.If            : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Nil           : ParseRule(&literal,  null,    Precedence.None),
+	Token.Type.Or            : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Print         : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Return        : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Super         : ParseRule(null,      null,    Precedence.None),
+	Token.Type.This          : ParseRule(null,      null,    Precedence.None),
+	Token.Type.True          : ParseRule(&literal,  null,    Precedence.None),
+	Token.Type.Var           : ParseRule(null,      null,    Precedence.None),
+	Token.Type.While         : ParseRule(null,      null,    Precedence.None),
+	Token.Type.Error         : ParseRule(null,      null,    Precedence.None),
+	Token.Type.EOF           : ParseRule(null,      null,    Precedence.None),
+];
+
diff --git a/src/clox/scanner.d b/src/clox/scanner.d
new file mode 100644
index 0000000..d916993
--- /dev/null
+++ b/src/clox/scanner.d
@@ -0,0 +1,157 @@
+module clox.scanner;
+
+import std.stdio;
+import std.ascii;
+
+import common.util;
+
+struct Token{
+	enum Type : ubyte {
+		None, Error, EOF, // Special
+		LeftParen, RightParen, // Single-character tokens.
+		LeftBrace, RightBrace,
+		Comma, Dot, Minus, Plus,
+		Semicolon, Slash, Star,
+		Bang, BangEqual, // One or two character tokens.
+		Equal, EqualEqual,
+		Greater, GreaterEqual,
+		Less, LessEqual,
+		Identifier, String, Number, // Literals.
+		And, Class, Else, False, // Keywords.
+		For, Fun, If, Nil, Or,
+		Print, Return, Super, This,
+		True, Var, While,
+	}
+	Type type;
+	int line;
+	string lexeme;
+	static Token error(string msg) nothrow @nogc => Token(Token.Type.Error, 0, msg);
+}
+
+struct Scanner{
+	nothrow:
+	@nogc:
+	string start;
+	string current;
+	int line = 1;
+	this(string source) @nogc nothrow{
+		start = current = source;
+	}
+	bool isAtEnd() const => current.length == 0;
+	private char peek() const => current[0];
+	private char peekNext() const => current.length >= 2 ? current[1] : '\0';
+	private Token makeToken(Token.Type type) const{
+		Token token;
+		token.type = type;
+		token.lexeme = start[0 .. current.ptr - start.ptr];
+		token.line = line;
+		return token;
+	}
+	private char advance(){
+		char c = current[0];
+		current = current[1 .. $];
+		return c;
+	}
+	private bool match(char needle){
+		if(isAtEnd || current[0] != needle)
+			return false;
+		current = current[1 .. $];
+		return true;
+	}
+	private void skipWhitespace(){
+		while(!isAtEnd){
+			char c = peek();
+			if(!c)
+				return;
+			if(c == '/' && peekNext() == '/'){
+				while(!isAtEnd && peek() != '\n')
+					advance();
+				continue;
+			}
+			if(!c.isWhite)
+				return;
+			/* debug writeln(c == '\n'); */
+			if(c == '\n')
+				line++;
+			current = current[1 .. $];
+		}
+	}
+	private Token parseString(){
+		while(peek() != '"' && !isAtEnd){
+			if(peek() == '\n')
+				line++;
+			advance();
+		}
+		if(isAtEnd)
+			return Token.error("Unterminated string.");
+		advance();
+		return makeToken(Token.Type.String);
+	}
+	private Token parseNumber(){
+		while(peek().isDigit)
+			advance();
+		if(peek() == '.' && peekNext().isDigit){
+			advance();
+			while(peek().isDigit)
+				advance();
+		}
+		return makeToken(Token.Type.Number);
+	}
+	private Token parseIdentifier(){
+		while(peek().isAlphaNum_)
+			advance();
+		Token token = makeToken(Token.Type.Identifier);
+		switch(token.lexeme){
+			case "and": token.type = Token.Type.And; break;
+			case "class": token.type = Token.Type.Class; break;
+			case "else": token.type = Token.Type.Else; break;
+			case "if": token.type = Token.Type.If; break;
+			case "nil": token.type = Token.Type.Nil; break;
+			case "or": token.type = Token.Type.Or; break;
+			case "print": token.type = Token.Type.Print; break;
+			case "return": token.type = Token.Type.Return; break;
+			case "super": token.type = Token.Type.Super; break;
+			case "var": token.type = Token.Type.Var; break;
+			case "while": token.type = Token.Type.While; break;
+			case "false": token.type = Token.Type.False; break;
+			case "for": token.type = Token.Type.For; break;
+			case "fun": token.type = Token.Type.Fun; break;
+			case "this": token.type = Token.Type.This; break;
+			case "true": token.type = Token.Type.True; break;
+			default: break;
+		}
+		return token;
+	}
+	Token scan(){
+		skipWhitespace();
+		start = current;
+		if(isAtEnd)
+			return Token(Token.Type.EOF);
+		char c = advance();
+		if(c.isAlpha_)
+			return parseIdentifier();
+		switch(c){
+			case '(': return makeToken(Token.Type.LeftParen);
+			case ')': return makeToken(Token.Type.RightParen);
+			case '{': return makeToken(Token.Type.LeftBrace);
+			case '}': return makeToken(Token.Type.RightBrace);
+			case ';': return makeToken(Token.Type.Semicolon);
+			case ',': return makeToken(Token.Type.Comma);
+			case '.': return makeToken(Token.Type.Dot);
+			case '-': return makeToken(Token.Type.Minus);
+			case '+': return makeToken(Token.Type.Plus);
+			case '/': return makeToken(Token.Type.Slash);
+			case '*': return makeToken(Token.Type.Star);
+			case '!': return makeToken(match('=') ? Token.Type.BangEqual : Token.Type.Bang);
+			case '=': return makeToken(match('=') ? Token.Type.EqualEqual : Token.Type.Equal);
+			case '<': return makeToken(match('=') ? Token.Type.LessEqual : Token.Type.Less);
+			case '>': return makeToken(match('=') ? Token.Type.GreaterEqual : Token.Type.Greater);
+			case '"': return parseString();
+			default: break;
+		}
+		if(c.isDigit)
+			return parseNumber();
+		return Token.error("Unexpected character.");
+	}
+}
+
diff --git a/src/clox/util.d b/src/clox/util.d
new file mode 100644
index 0000000..45c0945
--- /dev/null
+++ b/src/clox/util.d
@@ -0,0 +1,6 @@
+module clox.util;
+
+import std.stdio;
+import std.traits : isUnsigned;
+import std.container.array;
+
diff --git a/src/clox/value.d b/src/clox/value.d
new file mode 100644
index 0000000..1914616
--- /dev/null
+++ b/src/clox/value.d
@@ -0,0 +1,53 @@
+module clox.value;
+
+import std.stdio;
+
+import clox.container.vartype;
+
+/* struct Value{ */
+/* 	alias T = VarType!u; */
+/* 	private union U{ */
+/* 		bool bln; */
+/* 		bool nil; */
+/* 		double num; */
+/* 	} */
+/* 	T v; */
+/* 	alias v this; */
+/* } */
+	private union U{
+		bool bln;
+		bool nil;
+		double num;
+	}
+alias Value = VarType!U;
+
+void printValue(Value value){
+	final switch(value.type){
+		case value.Type.Bln: writef("%s", value.getBln); break;
+		case value.Type.Num: writef("%g", value.getNum); break;
+		case value.Type.Nil: writef("nil"); break;
+		case value.Type.None: assert(0);
+	}
+}
+bool isTruthy(Value value) nothrow @nogc {
+	final switch(value.type){
+		case value.Type.Bln: return value.getBln;
+		case value.Type.Num: return true;
+		case value.Type.Nil: return false;
+		case value.Type.None: assert(0);
+	}
+}
+bool isFalsey(Value value) nothrow @nogc {
+	return !isTruthy(value);
+}
+bool compare(string op)(Value a, Value b){
+	if(a.type != b.type)
+		return false;
+	final switch(a.type){
+		case a.Type.Bln: return mixin("a.getBln", op, "b.getBln");
+		case a.Type.Num: return mixin("a.getNum", op, "b.getNum");
+		case a.Type.Nil: return true;
+		case a.Type.None: assert(0);
+	}
+}
+
diff --git a/src/clox/vm.d b/src/clox/vm.d
new file mode 100644
index 0000000..485a626
--- /dev/null
+++ b/src/clox/vm.d
@@ -0,0 +1,114 @@
+module clox.vm;
+
+import std.stdio;
+
+import clox.chunk;
+import clox.value;
+import clox.dbg;
+import clox.util;
+import clox.compiler;
+import clox.container.stack;
+import clox.container.varint;
+import clox.container.int24;
+
+enum stackMax = 256;
+
+struct VM{
+	const(ubyte)* ip;
+	Stack!(Value, stackMax) stack;
+	Chunk* chunk;
+	enum InterpretResult{ Ok, CompileError, RuntimeError }
+	this(int _) @nogc nothrow {
+		stack = typeof(stack)(0);
+	}
+	InterpretResult interpret(string source){
+		Chunk c = Chunk();
+		Compiler compiler;
+		if(!compiler.compile(source, &c))
+			return InterpretResult.CompileError;
+		chunk = &c;
+		return interpret(chunk);
+	}
+	InterpretResult interpret(Chunk* chunk){
+		this.chunk = chunk;
+		ip = &chunk.code[0];
+		return run();
+	}
+	private void runtimeError(Args...)(string format, Args args) nothrow {
+		size_t instruction = ip - (&chunk.code[0]) - 1;
+		uint line = chunk.lines[instruction].toUint;
+		try{
+			stderr.writef("[line %d] ", line);
+			stderr.writefln(format, args);
+		} catch(Exception){}
+		/* stack.reset(); */
+	}
+	private InterpretResult run() nothrow {
+		auto readByte() => *ip++;
+		auto readIns() => cast(OpCode)readByte();
+		Value readConstant(){
+			VarUint constant = VarUint.read(ip[0 .. 4]);
+			ip += constant.len;
+			return chunk.constants[constant.i];
+		}
+		Value peek(int distance = 0){
+			return stack.top[-1 - distance];
+		}
+		while(true){
+			debug(traceExec){
+				writeln("          ", stack.live);
+				disassembleInstruction(chunk, ip - &chunk.code[0]);
+			}
+			OpCode instruction = readIns();
+			with(OpCode) opSwitch: final switch(instruction){
+				case Constant:
+					Value constant = readConstant();
+					stack.push(constant);
+					break;
+				case True:
+					stack.push(Value.bln(true));
+					break;
+				case False:
+					stack.push(Value.bln(false));
+					break;
+				case Nil:
+					stack.push(Value.nil());
+					break;
+				static foreach(k, op; [ Add: "+", Subtract: "-", Multiply: "*", Divide: "/" ]){
+					case k:
+						if(!peek(0).isNum || !peek(1).isNum){
+							runtimeError("Operands must be numbers.");
+							return InterpretResult.RuntimeError;
+						}
+						double b = stack.pop().getNum;
+						double a = stack.pop().getNum;
+						stack.push(Value.num(mixin("a", op, "b")));
+						break opSwitch;
+				}
+				static foreach(k, op; [ NotEqual: "!=", Equal: "==", Greater: ">", GreaterEqual: ">=", Less: "<", LessEqual: "<=" ]){
+					case k:
+						Value b = stack.pop();
+						Value a = stack.pop();
+						stack.push(Value.bln(compare!op(a, b)));
+						break opSwitch;
+				}
+				case Not:
+					stack.push(Value.bln(stack.pop().isFalsey));
+					break;
+				case Negate:
+					if(!peek(0).isNum){
+						runtimeError("Operand must be a number.");
+						return InterpretResult.RuntimeError;
+					}
+					stack.push(Value.num(-stack.pop().getNum));
+					break;
+				case Return:
+					debug printValue(stack.pop());
+					debug writeln();
+					return InterpretResult.Ok;
+			}
+		}
+		assert(0);
+	}
+}
+
diff --git a/src/common/util.d b/src/common/util.d
index 14e0917..a6876ba 100644
--- a/src/common/util.d
+++ b/src/common/util.d
@@ -6,3 +6,39 @@ template defaultCtor(){
 			this.tupleof[i] = a;
 	}
 }
+
+import std.ascii : isAlpha, isAlphaNum;
+bool isAlpha_(dchar c)    @nogc nothrow @safe => c.isAlpha    || c == '_';
+bool isAlphaNum_(dchar c) @nogc nothrow @safe => c.isAlphaNum || c == '_';
+
+T pop(T)(ref T[] arr){
+	T v = arr.last;
+	arr.length--;
+	return v;
+}
+T shift(T)(ref T[] arr){
+	T v = arr.first;
+	arr = arr[1 .. $];
+	return v;
+}
+ref T sole(T)(T[] arr) @nogc @safe pure{
+	assert(arr.length == 1, "Not sole");
+	return arr[0];
+}
+ref T first(T)(T[] arr) @nogc @safe pure{
+	assert(arr.length >= 1, "No first");
+	return arr[0];
+}
+ref T second(T)(T[] arr) @nogc @safe pure{
+	assert(arr.length >= 2, "No second");
+	return arr[1];
+}
+ref T third(T)(T[] arr) @nogc @safe pure{
+	assert(arr.length >= 3, "No third");
+	return arr[2];
+}
+ref T last(T)(T[] arr) @nogc @safe pure{
+	assert(arr.length >= 1, "No last");
+	return arr[$-1];
+}
+
diff --git a/src/jlox/environment.d b/src/jlox/environment.d
index 06023dc..b1d32bd 100644
--- a/src/jlox/environment.d
+++ b/src/jlox/environment.d
@@ -6,26 +6,40 @@ import common.util;
 
 class Environment{
 	Environment enclosing;
-	private TValue[string] values;
+	private LoxValue[string] values;
 
 	mixin defaultCtor;
 
-	void define(string name, TValue value){
+	void define(string name, LoxValue value){
 		values[name] = value;
 	}
-	TValue get(Token name){
-		if(TValue* value = name.lexeme in values)
+	LoxValue get(Token name){
+		if(LoxValue* value = name.lexeme in values)
 			return *value;
 		if(enclosing)
 			return enclosing.get(name);
 		throw new RuntimeError(name, "Undefined variable '" ~ name.lexeme ~ "'.");
 	}
-	void assign(Token name, TValue value){
-		if(name.lexeme in values)
-			return values[name.lexeme] = value;
+	Environment ancestor(uint distance){
+		Environment environment = this;
+		for(uint i = 0; i < distance; i++)
+			environment = environment.enclosing;
+		return environment;
+	}
+	LoxValue getAt(uint distance, string name){
+		return ancestor(distance).values[name];
+	}
+	void assign(Token name, LoxValue value){
+		if(name.lexeme in values){
+			values[name.lexeme] = value;
+			return;
+		}
 		if(enclosing)
 			return enclosing.assign(name, value);
 		throw new RuntimeError(name, "Undefined variable '" ~ name.lexeme ~ "'.");
 	}
+	void assignAt(uint distance, Token name, LoxValue value){
+		ancestor(distance).values[name.lexeme] = value;
+	}
 }
 
diff --git a/src/jlox/expr.d b/src/jlox/expr.d
index 2aea4b1..f95a4ff 100644
--- a/src/jlox/expr.d
+++ b/src/jlox/expr.d
@@ -4,8 +4,6 @@ import std.conv;
 import std.stdio;
 import std.meta : AliasSeq;
 
-import taggedalgebraic;
-
 import jlox.token;
 import jlox.tokentype;
 import common.util;
@@ -15,13 +13,17 @@ abstract class Expr{
 		R visit(Assign expr);
 		R visit(Binary expr);
 		R visit(Call expr);
+		R visit(Get expr);
 		R visit(Grouping expr);
 		R visit(Literal expr);
 		R visit(Logical expr);
+		R visit(Set expr);
+		R visit(Super expr);
+		R visit(This expr);
 		R visit(Unary expr);
 		R visit(Variable expr);
 	}
-	private alias rTypes = AliasSeq!(string, TValue);
+	private alias rTypes = AliasSeq!(string, LoxValue, void);
 	static foreach(T; rTypes)
 		abstract T accept(Visitor!T visitor);
 	private template defCtorAndAccept(){
@@ -47,12 +49,17 @@ abstract class Expr{
 		Expr[] arguments;
 		mixin defCtorAndAccept;
 	}
+	static class Get : typeof(this){
+		Expr object;
+		Token name;
+		mixin defCtorAndAccept;
+	}
 	static class Grouping : typeof(this){
 		Expr expression;
 		mixin defCtorAndAccept;
 	}
 	static class Literal : typeof(this){
-		TValue value;
+		LoxValue value;
 		mixin defCtorAndAccept;
 	}
 	static class Logical : typeof(this){
@@ -61,6 +68,21 @@ abstract class Expr{
 		Expr right;
 		mixin defCtorAndAccept;
 	}
+	static class Set : typeof(this){
+		Expr object;
+		Token name;
+		Expr value;
+		mixin defCtorAndAccept;
+	}
+	static class Super : typeof(this){
+		Token keyword;
+		Token method;
+		mixin defCtorAndAccept;
+	}
+	static class This : typeof(this){
+		Token keyword;
+		mixin defCtorAndAccept;
+	}
 	static class Unary : typeof(this){
 		Token operator;
 		Expr right;
@@ -72,31 +94,3 @@ abstract class Expr{
 	}
 }
 
-/* class AstPrinter : Expr.Visitor!string{ */
-/* 	string print(Expr expr){ */
-/* 		return expr.accept(this); */
-/* 	} */
-/* 	string parenthesize(Args...)(string name, Args args){ */
-/* 		string s = "(" ~ name; */
-/* 		static foreach(expr; args){ */
-/* 			s ~= " "; */
-/* 			s ~= expr.accept(this); */
-/* 		} */
-/* 		return s ~ ")"; */
-/* 	} */
-/* 	string visit(Expr.Binary expr){ */
-/* 		return parenthesize(expr.operator.lexeme, expr.left, expr.right); */
-/* 	} */
-/* 	string visit(Expr.Grouping expr){ */
-/* 		return parenthesize("group", expr.expression); */
-/* 	} */
-/* 	string visit(Expr.Literal expr){ */
-/* 		if(expr.value.isNil) */
-/* 			return "nil"; */
-/* 		return expr.value.to!string; */
-/* 	} */
-/* 	string visit(Expr.Unary expr){ */
-/* 		return parenthesize(expr.operator.lexeme, expr.right); */
-/* 	} */
-/* } */
-
diff --git a/src/jlox/interpreter.d b/src/jlox/interpreter.d
index d248eda..15870bc 100644
--- a/src/jlox/interpreter.d
+++ b/src/jlox/interpreter.d
@@ -1,6 +1,7 @@
 module jlox.interpreter;
 
 import std.conv;
+import std.exception : enforce;
 import std.stdio;
 import std.algorithm;
 import std.array;
@@ -11,10 +12,12 @@ import jlox.expr;
 import jlox.stmt;
 import jlox.token;
 import jlox.tokentype;
-import jlox.token : TValue;
+import jlox.token : LoxValue;
 import jlox.main;
 import jlox.environment;
 import jlox.loxfunction;
+import jlox.loxclass;
+import jlox.loxinstance;
 
 class RuntimeError : Exception{
 	const Token token;
@@ -24,14 +27,14 @@ class RuntimeError : Exception{
 	}
 }
 class Return : Exception{
-	const TValue value;
-	this(TValue value){
+	const LoxValue value;
+	this(LoxValue value){
 		super(null);
 		this.value = value;
 	}
 }
 
-class Interpreter : Stmt.Visitor!void, Expr.Visitor!TValue {
+class Interpreter : Stmt.Visitor!void, Expr.Visitor!LoxValue {
 	Environment globals = new Environment();
 	private Environment environment;
 	this(){
@@ -39,20 +42,24 @@ class Interpreter : Stmt.Visitor!void, Expr.Visitor!TValue {
 
 		import std.datetime.stopwatch;
 		auto sw = StopWatch(AutoStart.yes);
-		globals.define("clock", TValue.cal(new class LoxCallable{
+		globals.define("clock", new class LoxCallable{
 			int arity() => 0;
-			TValue call(Interpreter interpreter, TValue[] arguments) => TValue.dbl(sw.peek.total!"usecs" / (1000.0 * 1000.0));
-		}));
+			LoxValue call(Interpreter interpreter, LoxValue[] arguments) => new LoxNum(sw.peek.total!"usecs" / (1000.0 * 1000.0));
+			override string toString() const => "<native clock>";
+		});
 
 		version(LoxExtraNativeFuncs){
-			globals.define("sleep", TValue.cal(new class LoxCallable{
+			globals.define("sleep", new class LoxCallable{
 				int arity() => 1;
 				import core.thread.osthread;
-				TValue call(Interpreter interpreter, TValue[] arguments){
-					Thread.sleep(dur!"usecs"(cast(long)(arguments[0].dblValue * 1000 * 1000)));
-					return TValue.nil(tvalueNil);
+				LoxValue call(Interpreter interpreter, LoxValue[] arguments){
+					if(cast(LoxNum)arguments[0] is null)
+						throw new RuntimeError(null, "Expected number to sleep/1");
+					Thread.sleep(dur!"usecs"(cast(long)(cast(LoxNum)arguments[0] * 1000 * 1000)));
+					return new LoxNil();
 				}
-			}));
+				override string toString() const => "<native sleep>";
+			});
 		}
 	}
 	void interpret(Stmt[] statements){ 
@@ -76,38 +83,59 @@ class Interpreter : Stmt.Visitor!void, Expr.Visitor!TValue {
 			this.environment = previous;
 		}
 	}
-	private TValue evaluate(Expr expr){
+	private LoxValue evaluate(Expr expr){
 		return expr.accept(this);
 	}
-	private bool isTruthy(TValue val){
-		switch(val.kind){
-			case TValue.Kind.nil:
-				return false;
-			case TValue.Kind.bln:
-				return val.blnValue;
-			default:
-				return true;
-		}
+	private bool isTruthy(LoxValue val){
+		if(cast(LoxNil)val)
+			return false;
+		if(auto b = cast(LoxBool)val)
+			return b;
+		return true;
 	}
-	private bool isEqual(TValue a, TValue b){
-		return a == b;
+	private bool isEqual(LoxValue a, LoxValue b){
+		return a.equals(b);
 	}
-	private void checkNumberOperand(Token operator, TValue operand){
-		if(operand.kind == TValue.Kind.dbl)
+	private void checkNumberOperand(Token operator, LoxValue operand){
+		if(cast(LoxNum)operand)
 			return;
 		throw new RuntimeError(operator, "Operand must be a number.");
 	}
-
+	private uint[Expr] locals;
+	void resolve(Expr expr, uint depth){
+		locals[expr] = depth;
+	}
 
 	void visit(Stmt.Block stmt){
 		executeBlock(stmt.statements, new Environment(environment));
 	}
+	void visit(Stmt.Class stmt){
+		LoxValue superclass;
+		if(stmt.superclass !is null){
+			superclass = evaluate(stmt.superclass);
+			enforce(cast(LoxClass)superclass, new RuntimeError(stmt.superclass.name, "Superclass must be a class."));
+		}
+		environment.define(stmt.name.lexeme, new LoxNil());
+		if(stmt.superclass !is null){
+			environment = new Environment(environment);
+			environment.define("super", superclass);
+		}
+		LoxFunction[string] methods;
+		foreach(Stmt.Function method; stmt.methods){
+			LoxFunction func = new LoxFunction(method, environment, method.name.lexeme == "init");
+			methods[method.name.lexeme] = func;
+		}
+		LoxClass cls = new LoxClass(stmt.name.lexeme, cast(LoxClass)superclass, methods);
+		if(superclass !is null)
+			environment = environment.enclosing;
+		environment.assign(stmt.name, cls);
+	}
 	void visit(Stmt.Expression stmt){
 		evaluate(stmt.expression);
 	}
 	void visit(Stmt.Function stmt){
-		LoxFunction func = new LoxFunction(stmt, environment);
-		environment.define(stmt.name.lexeme, TValue.cal(func));
+		LoxFunction func = new LoxFunction(stmt, environment, false);
+		environment.define(stmt.name.lexeme, func);
 	}
 	void visit(Stmt.If stmt){
 		if(isTruthy(evaluate(stmt.condition)))
@@ -116,41 +144,45 @@ class Interpreter : Stmt.Visitor!void, Expr.Visitor!TValue {
 			execute(stmt.elseBranch);
 	}
 	void visit(Stmt.Print stmt){
-		TValue value = evaluate(stmt.expression);
-		writeln(tvalueToString(value));
+		version(LoxPrintMultiple){
+			writeln(stmt.expressions.map!(x => evaluate(x)).map!(x => x.toString).join('\t'));
+		} else {
+			LoxValue value = evaluate(stmt.expression);
+			writeln(value.toString);
+		}
 	}
 	void visit(Stmt.Return stmt){
-		TValue value = stmt.value !is null ? evaluate(stmt.value) : TValue.nil(tvalueNil);
+		LoxValue value = stmt.value !is null ? evaluate(stmt.value) : new LoxNil();
 		throw new Return(value);
 	}
 	void visit(Stmt.Var stmt){
-		environment.define(stmt.name.lexeme, stmt.initialiser is null ? TValue.nil(tvalueNil) : evaluate(stmt.initialiser));
+		environment.define(stmt.name.lexeme, stmt.initialiser is null ? new LoxNil() : evaluate(stmt.initialiser));
 	}
 	void visit(Stmt.While stmt){
 		while(isTruthy(evaluate(stmt.condition)))
 			execute(stmt.body);
 	}
 
-	TValue visit(Expr.Literal expr){
+	LoxValue visit(Expr.Literal expr){
 		return expr.value;
 	}
-	TValue visit(Expr.Grouping expr){
+	LoxValue visit(Expr.Grouping expr){
 		return evaluate(expr.expression);
 	}
-	TValue visit(Expr.Unary expr){
-		TValue right = evaluate(expr.right);
+	LoxValue visit(Expr.Unary expr){
+		LoxValue right = evaluate(expr.right);
 		switch(expr.operator.type){
 			case TokenType.MINUS:
 				checkNumberOperand(expr.operator, right);
-				return TValue.dbl(-right.dblValue);
+				return new LoxNum(-cast(LoxNum)right);
 			case TokenType.BANG:
-				return TValue.bln(!isTruthy(right));
+				return new LoxBool(!isTruthy(right));
 			default:
 				assert(0);
 		}
 	}
-	TValue visit(Expr.Logical expr){
-		TValue left = evaluate(expr.left);
+	LoxValue visit(Expr.Logical expr){
+		LoxValue left = evaluate(expr.left);
 		if(expr.operator.type == TokenType.OR){
 			if(isTruthy(left))
 				return left;
@@ -160,59 +192,84 @@ class Interpreter : Stmt.Visitor!void, Expr.Visitor!TValue {
 		}
 		return evaluate(expr.right);
 	}
-	TValue visit(Expr.Binary expr){
-		TValue left = evaluate(expr.left);
-		TValue right = evaluate(expr.right); 
-		static string m(TokenType t, string op, string v, string vv){
-			return q{case %s:
-				checkNumberOperand(expr.operator, left);
-				checkNumberOperand(expr.operator, right);
-				return TValue.%s( left.%s %s right.%s );
-			}.format(t, v, vv, op, vv);
-		}
+	LoxValue visit(Expr.Set expr){
+		LoxValue object = evaluate(expr.object);
+		if(!(cast(LoxInstance)object))
+			throw new RuntimeError(expr.name, "Only instances have fields.");
+		LoxValue value = evaluate(expr.value);
+		(cast(LoxInstance)object).set(expr.name, value);
+		return value;
+	}
+	LoxValue visit(Expr.Super expr){
+		uint distance = locals[expr];
+		LoxClass superclass = cast(LoxClass)environment.getAt(distance, "super");
+		LoxInstance object = cast(LoxInstance)environment.getAt(distance - 1, "this");
+		LoxFunction method = superclass.findMethod(expr.method.lexeme);
+		if(method is null)
+			throw new RuntimeError(expr.method, "Undefined property '" ~ expr.method.lexeme ~ "'.");
+		return method.bind(object);
+	}
+	LoxValue visit(Expr.This expr){
+		return lookUpVariable(expr.keyword, expr);
+	}
+	LoxValue visit(Expr.Binary expr){
+		LoxValue left = evaluate(expr.left);
+		LoxValue right = evaluate(expr.right); 
 		with(TokenType) switch(expr.operator.type){
-			static foreach(t, op; [ MINUS: "-", SLASH: "/", STAR: "*" ])
-				mixin(ctEval!(m(t, op, "dbl", "dblValue")));
-
-			case PLUS:
-				if(left.isDbl && right.isDbl)
-					return TValue.dbl(left.dblValue + right.dblValue);
-				else if(left.isStr && right.isStr)
-					return TValue.str(left.strValue ~ right.strValue);
-				version(LoxConcatNonStrings){
-					if(left.isStr || right.isStr)
-						return TValue.str(tvalueToString(left) ~ tvalueToString(right));
-				}
-				checkNumberOperand(expr.operator, left);
-				checkNumberOperand(expr.operator, right);
-
-			static foreach(t, op; [ GREATER: ">", GREATER_EQUAL: ">=", LESS: "<", LESS_EQUAL: "<=" ])
-				mixin(ctEval!(m(t, op, "bln", "dblValue")));
+			static foreach(t, op; [ PLUS: "+", MINUS: "-", SLASH: "/", STAR: "*", GREATER: ">", GREATER_EQUAL: ">=", LESS: "<", LESS_EQUAL: "<=" ]){
+				case t:
+					static if(t == PLUS){
+						if(cast(LoxStr)left && cast(LoxStr)right)
+							return new LoxStr(cast(LoxStr)left ~ cast(LoxStr)right);
+						version(LoxConcatNonStrings){
+							if(cast(LoxStr)left || cast(LoxStr)right)
+								return new LoxStr(left.toString ~ right.toString);
+						}
+					}
+					checkNumberOperand(expr.operator, left);
+					checkNumberOperand(expr.operator, right);
+					return (cast(LoxNum)left).opBinary!op(cast(LoxNum)right);
+			}
 
 			case BANG_EQUAL:
-				return TValue.bln(!isEqual(left, right));
+			return new LoxBool(!isEqual(left, right));
 			case EQUAL_EQUAL:
-				return TValue.bln(isEqual(left, right));
+			return new LoxBool(isEqual(left, right));
 			default:
-				assert(0);
+			assert(0);
 		}
 	}
-	TValue visit(Expr.Call expr){
-		TValue callee = evaluate(expr.callee);
-		if(!callee.isCal)
+	LoxValue visit(Expr.Call expr){
+		LoxValue callee = evaluate(expr.callee);
+		if(!cast(LoxCallable)callee)
 			throw new RuntimeError(expr.paren, "Can only call functions and classes.");
 		auto arguments = expr.arguments.map!(a => evaluate(a));
-		LoxCallable func = callee.calValue;
+		LoxCallable func = cast(LoxCallable)callee;
 		if(arguments.length != func.arity())
 			throw new RuntimeError(expr.paren, "Expected " ~ func.arity().to!string ~ " arguments but got " ~ arguments.length.to!string ~ ".");
 		return func.call(this, arguments.array);
 	}
-	TValue visit(Expr.Variable expr){
-		return environment.get(expr.name);
+	LoxValue visit(Expr.Get expr){
+		LoxValue object = evaluate(expr.object);
+		if(auto ins = cast(LoxInstance)object)
+			return ins.get(expr.name);
+		throw new RuntimeError(expr.name, "Only instances have properties.");
 	}
-	TValue visit(Expr.Assign expr){
-		TValue value = evaluate(expr.value);
-		environment.assign(expr.name, value);
+	LoxValue visit(Expr.Variable expr){
+		return lookUpVariable(expr.name, expr);
+	}
+	private LoxValue lookUpVariable(Token name, Expr expr){
+		if(const distance = expr in locals)
+			return environment.getAt(*distance, name.lexeme);
+		else
+			return globals.get(name);
+	}
+	LoxValue visit(Expr.Assign expr){
+		LoxValue value = evaluate(expr.value);
+		if(const distance = expr in locals)
+			environment.assignAt(*distance, expr.name, value);
+		else
+			globals.assign(expr.name, value);
 		return value;
 	}
 }
diff --git a/src/jlox/loxclass.d b/src/jlox/loxclass.d
new file mode 100644
index 0000000..44be38a
--- /dev/null
+++ b/src/jlox/loxclass.d
@@ -0,0 +1,37 @@
+module jlox.loxclass;
+
+import jlox.token;
+import jlox.interpreter;
+import jlox.loxinstance;
+import jlox.loxfunction;
+import common.util;
+
+class LoxClass : LoxCallable{
+	package const string name;
+	private const LoxClass superclass;
+	private const LoxFunction[string] methods;
+	mixin defaultCtor;
+
+	LoxFunction findMethod(string name) const{
+		if(auto method = name in methods)
+			return cast(LoxFunction)*method;
+		if(superclass !is null)
+			return superclass.findMethod(name);
+		return null;
+	}
+
+	int arity(){
+		if(auto initialiser = findMethod("init"))
+			return initialiser.arity();
+		return 0;
+	}
+	LoxValue call(Interpreter interpreter, LoxValue[] arguments){
+		LoxInstance instance = new LoxInstance(this);
+		LoxFunction initialiser = findMethod("init");
+		if(initialiser !is null)
+			initialiser.bind(instance).call(interpreter, arguments);
+		return instance;
+	}
+	override string toString() const => "class";
+}
+
diff --git a/src/jlox/loxfunction.d b/src/jlox/loxfunction.d
index 85bbb32..504369e 100644
--- a/src/jlox/loxfunction.d
+++ b/src/jlox/loxfunction.d
@@ -2,31 +2,44 @@ module jlox.loxfunction;
 
 import std.conv;
 
+import common.util;
 import jlox.token;
 import jlox.stmt;
 import jlox.interpreter;
 import jlox.environment;
-import common.util;
+import jlox.loxinstance;
 
 class LoxFunction : LoxCallable{
 	private Stmt.Function declaration;
 	private Environment closure;
+	private const bool isInitialiser;
 	mixin defaultCtor;
 	invariant{
 		assert(declaration && closure);
 	}
+
+	LoxFunction bind(LoxInstance instance){
+		Environment environment = new Environment(closure);
+		environment.define("this", instance);
+		return new LoxFunction(declaration, environment, isInitialiser);
+	}
 	
 	int arity() => declaration.params.length.to!int;
-	TValue call(Interpreter interpreter, TValue[] arguments){
+	LoxValue call(Interpreter interpreter, LoxValue[] arguments){
 		Environment environment = new Environment(closure);
 		foreach(i; 0 .. declaration.params.length)
 			environment.define(declaration.params[i].lexeme, arguments[i]);
 		try{
 			interpreter.executeBlock(declaration.body, environment);
 		} catch(Return returnValue){
-			return returnValue.value;
+			if(isInitialiser)
+				return closure.getAt(0, "this");
+			return cast(LoxValue)returnValue.value;
 		}
-		return TValue.nil(tvalueNil);
+		if(isInitialiser)
+			return closure.getAt(0, "this");
+		return new LoxNil();
 	}
+	override string toString() const => "function";
 }
 
diff --git a/src/jlox/loxinstance.d b/src/jlox/loxinstance.d
new file mode 100644
index 0000000..f30d858
--- /dev/null
+++ b/src/jlox/loxinstance.d
@@ -0,0 +1,27 @@
+module jlox.loxinstance;
+
+import std.format : format;
+
+import jlox.token;
+import jlox.interpreter;
+import jlox.loxclass;
+import common.util;
+
+class LoxInstance : LoxValue{
+	private LoxClass cls;
+	private LoxValue[string] fields;
+	mixin defaultCtor;
+	override string toString() const => "<instance %s>".format(cls.name);
+
+	LoxValue get(Token name){
+		if(auto v = name.lexeme in fields)
+			return *v;
+		if(auto method = cls.findMethod(name.lexeme))
+			return method.bind(this);
+		throw new RuntimeError(name, "Undefined property '" ~ name.lexeme ~ "'.");
+	}
+	void set(Token name, LoxValue value){
+		fields[name.lexeme] = value;
+	}
+}
+
diff --git a/src/jlox/main.d b/src/jlox/main.d
index 51e0e33..17f176a 100644
--- a/src/jlox/main.d
+++ b/src/jlox/main.d
@@ -14,6 +14,11 @@ import jlox.parser;
 import jlox.interpreter;
 import jlox.expr;
 import jlox.stmt;
+import jlox.resolver;
+
+enum RetVal{
+	success = 0, other = 1, runtime = 2
+}
 
 private class MainException : Exception{
 	this(){
@@ -42,7 +47,10 @@ static class Lox{
 		hadError = true;
 	}
 	static void runtimeError(RuntimeError error){
-		stderr.writeln(error.msg ~ "\n[line " ~ error.token.line.to!string ~ "]");
+		if(error.token)
+			stderr.writeln(error.msg ~ "\n[line " ~ error.token.line.to!string ~ "]");
+		else
+			stderr.writeln(error.msg);
 		hadRuntimeError = true;
 	}
 
@@ -52,7 +60,11 @@ static class Lox{
 
 		Parser parser = new Parser(tokens);
 		Stmt[] statements = parser.parse();
+		if(hadError)
+			return;
 
+		Resolver resolver = new Resolver(interpreter);
+		resolver.resolve(statements);
 		if(hadError)
 			return;
 
@@ -77,6 +89,8 @@ static class Lox{
 	}
 }
 
+extern(C) int isatty(int);
+
 int main(string[] argv){
 	auto args = new Program("lox")
 		.add(new Argument("path").optional.acceptsFiles)
@@ -85,17 +99,21 @@ int main(string[] argv){
 	try{
 		if(args.arg("path") && args.option("command")){
 			stderr.writeln("Cant have both path and --cmd");
-			return 3;
+			return RetVal.other;
 		}
-		if(auto cmd = args.option("command"))
+		if(auto cmd = args.option("command")){
 			Lox.run(cmd);
-		else if(auto path = args.arg("path"))
+		} else if(auto path = args.arg("path")){
 			Lox.runFile(path);
-		else
-			Lox.runPrompt();
+		} else {
+			if(isatty(stdin.fileno))
+				Lox.runPrompt();
+			else
+				Lox.runFile("/dev/stdin");
+		}
 	} catch(MainException rte){
-		return Lox.hadError ? 1 : 2;
+		return Lox.hadError ? RetVal.other : RetVal.runtime;
 	}
-	return 0;
+	return RetVal.success;
 }
 
diff --git a/src/jlox/parser.d b/src/jlox/parser.d
index 6ebc002..a314992 100644
--- a/src/jlox/parser.d
+++ b/src/jlox/parser.d
@@ -81,9 +81,18 @@ class Parser{
 	}
 
 	private Stmt printStatement(){
-		Expr value = expression();
-		consume(TokenType.SEMICOLON, "Expect ';' after value.");
-		return new Stmt.Print(value);
+		version(LoxPrintMultiple){
+			Expr[] values;
+			if(!check(TokenType.SEMICOLON)) do {
+				values ~= expression();
+			} while(match(TokenType.COMMA));
+			consume(TokenType.SEMICOLON, "Expect ';' after values.");
+			return new Stmt.Print(values);
+		} else {
+			Expr value = expression();
+			consume(TokenType.SEMICOLON, "Expect ';' after value.");
+			return new Stmt.Print(value);
+		}
 	}
 	private Stmt returnStatement(){
 		Token keyword = previous();
@@ -135,7 +144,7 @@ class Parser{
 		else
 			initialiser = expressionStatement();
 
-		Expr condition = check(TokenType.SEMICOLON) ? new Expr.Literal(TValue.bln(true)) : expression();
+		Expr condition = check(TokenType.SEMICOLON) ? new Expr.Literal(new LoxBool(true)) : expression();
 		consume(TokenType.SEMICOLON, "Expect ';' after loop condition.");
 
 		Expr increment;
@@ -188,8 +197,11 @@ class Parser{
 		if(match(TokenType.EQUAL)){
 			Token equals = previous();
 			Expr value = assignment();
-			if(auto v = cast(Expr.Variable)expr)
+			if(auto v = cast(Expr.Variable)expr){
 				return new Expr.Assign(v.name, value);
+			} else if(auto get = cast(Expr.Get)expr){
+				return new Expr.Set(get.object, get.name, value);
+			}
 			error(equals, "Invalid assignment target."); 
 		}
 		return expr;
@@ -271,10 +283,14 @@ class Parser{
 		}
 		Expr expr = primary();
 		while(true){ 
-			if(match(TokenType.LEFT_PAREN))
+			if(match(TokenType.LEFT_PAREN)){
 				expr = finishCall(expr);
-			else
+			} else if(match(TokenType.DOT)){
+				Token name = consume(TokenType.IDENTIFIER, "Expect property name after '.'.");
+				expr = new Expr.Get(expr, name);
+			} else {
 				break;
+			}
 		}
 		return expr;
 	}
@@ -282,18 +298,26 @@ class Parser{
 		if(match(TokenType.IDENTIFIER))
 			return new Expr.Variable(previous());
 		if(match(TokenType.FALSE))
-			return new Expr.Literal(TValue.bln(false));
+			return new Expr.Literal(new LoxBool(false));
 		if(match(TokenType.TRUE))
-			return new Expr.Literal(TValue.bln(true));
+			return new Expr.Literal(new LoxBool(true));
 		if(match(TokenType.NIL))
-			return new Expr.Literal(tvalueNil);
+			return new Expr.Literal(new LoxNil());
 		if(match(TokenType.NUMBER, TokenType.STRING))
 			return new Expr.Literal(previous().literal);
+		if(match(TokenType.THIS))
+			return new Expr.This(previous());
 		if(match(TokenType.LEFT_PAREN)){
 			Expr expr = expression();
 			consume(TokenType.RIGHT_PAREN, "Expect ')' after expression.");
 			return new Expr.Grouping(expr);
 		}
+		if(match(TokenType.SUPER)){
+			Token keyword = previous();
+			consume(TokenType.DOT, "Expect '.' after 'super'.");
+			Token method = consume(TokenType.IDENTIFIER, "Expect superclass method name.");
+			return new Expr.Super(keyword, method);
+		}
 		throw error(peek(), "Expect expression.");
 	}
 	private Stmt varDeclaration(){
@@ -304,12 +328,28 @@ class Parser{
 		consume(TokenType.SEMICOLON, "Expect ';' after variable declaration.");
 		return new Stmt.Var(name, initialiser);
 	}
+	private Stmt classDeclaration() {
+		Token name = consume(TokenType.IDENTIFIER, "Expect class name.");
+		Expr.Variable superclass;
+		if(match(TokenType.LESS)){
+			consume(TokenType.IDENTIFIER, "Expect superlcass name.");
+			superclass = new Expr.Variable(previous);
+		}
+		consume(TokenType.LEFT_BRACE, "Expect '{' before class body.");
+		Stmt.Function[] methods;
+		while(!check(TokenType.RIGHT_BRACE) && !isAtEnd)
+			methods ~= fun("method");
+		consume(TokenType.RIGHT_BRACE, "Expect '}' after class body.");
+		return new Stmt.Class(name, superclass, methods);
+	}
 	private Stmt declaration(){
 		try {
-			if(match(TokenType.FUN))
-				return fun("function");
 			if(match(TokenType.VAR))
 				return varDeclaration();
+			if(match(TokenType.FUN))
+				return fun("function");
+			if(match(TokenType.CLASS))
+				return classDeclaration();
 			return statement();
 		} catch(ParseError error){
 			synchronise();
diff --git a/src/jlox/resolver.d b/src/jlox/resolver.d
new file mode 100644
index 0000000..c9dbf81
--- /dev/null
+++ b/src/jlox/resolver.d
@@ -0,0 +1,198 @@
+module jlox.resolver;
+
+import std.container.slist;
+import std.stdio;
+import std.algorithm;
+import std.range : enumerate;
+
+import jlox.main;
+import jlox.token;
+import jlox.stmt;
+import jlox.expr;
+import jlox.interpreter;
+import common.util;
+
+class Resolver : Stmt.Visitor!void, Expr.Visitor!void {
+	private enum FunctionType{ NONE, FUNCTION, INITIALISER, METHOD }
+	private enum ClassType{ NONE, CLASS, SUBCLASS }
+	private Interpreter interpreter;
+	this(Interpreter interpreter){
+		this.interpreter = interpreter;
+	}
+	private FunctionType currentFunction = FunctionType.NONE;
+	private ClassType currentClass = ClassType.NONE;
+	private SList!(bool[string]) scopes;
+	private void resolve(Stmt stmt) => stmt.accept(this);
+	private void resolve(Expr expr) => expr.accept(this);
+	void resolve(Stmt[] statements){
+		foreach(statement; statements)
+			resolve(statement);
+	}
+	private void resolveLocal(Expr expr, Token name){
+		foreach(i, scp; scopes[].enumerate){
+			if(name.lexeme in scp){
+				interpreter.resolve(expr, cast(uint)i);
+				return;
+			}
+		}
+	}
+	private void resolveFunction(Stmt.Function func, FunctionType type){
+		FunctionType enclosingFunction = currentFunction;
+		currentFunction = type;
+		scope(exit)
+			currentFunction = enclosingFunction;
+		beginScope();
+		foreach(param; func.params){
+			declare(param);
+			define(param);
+		}
+		resolve(func.body);
+		endScope();
+	}
+	private void endScope() => scopes.removeFront();
+	private void beginScope(){
+		bool[string] s;
+		scopes.insertFront(s);
+	}
+	private void declare(Token name){
+		if(scopes.empty)
+			return;
+		bool[string] scp = scopes.front;
+		if(name.lexeme in scp)
+			Lox.error(name, "Already a variable with this name in this scope.");
+		scp[name.lexeme] = false;
+	}
+	private void define(Token name){
+		if(scopes.empty)
+			return;
+		scopes.front[name.lexeme] = true;
+	}
+
+	void visit(Stmt.Block stmt){
+		beginScope();
+		resolve(stmt.statements);
+		endScope();
+	}
+	void visit(Stmt.Class stmt){
+		ClassType enclosingClass = currentClass;
+		currentClass = ClassType.CLASS;
+		scope(exit)
+			currentClass = enclosingClass;
+		declare(stmt.name);
+		define(stmt.name);
+		if(stmt.superclass !is null){
+			currentClass = ClassType.SUBCLASS;
+			if(stmt.name.lexeme == stmt.superclass.name.lexeme)
+				Lox.error(stmt.superclass.name, "A class can't inherit from itself.");
+			resolve(stmt.superclass);
+		}
+		if(stmt.superclass !is null){
+			beginScope();
+			scopes.front["super"] = true;
+		}
+		beginScope();
+		scopes.front["this"] = true;
+		foreach(method; stmt.methods){
+			FunctionType declaration = FunctionType.METHOD;
+			if(method.name.lexeme == "init")
+				declaration = FunctionType.INITIALISER;
+			resolveFunction(method, declaration); 
+		}
+		endScope();
+		if(stmt.superclass !is null)
+			endScope();
+	}
+	void visit(Stmt.Var stmt){
+		declare(stmt.name);
+		if(stmt.initialiser !is null)
+			resolve(stmt.initialiser);
+		define(stmt.name);
+	}
+	void visit(Stmt.Function stmt){
+		declare(stmt.name);
+		define(stmt.name);
+		resolveFunction(stmt, FunctionType.FUNCTION);
+	}
+	void visit(Expr.Variable expr){
+		if(!scopes.empty && scopes.front.get(expr.name.lexeme, true) == false)
+			Lox.error(expr.name, "Can't read local variable in its own initializer.");
+		resolveLocal(expr, expr.name);
+	}
+	void visit(Expr.Assign expr){
+		resolve(expr.value);
+		resolveLocal(expr, expr.name);
+	}
+
+	void visit(Stmt.Expression stmt){
+		resolve(stmt.expression);
+	}
+	void visit(Stmt.If stmt){
+		resolve(stmt.condition);
+		resolve(stmt.thenBranch);
+		if(stmt.elseBranch !is null)
+			resolve(stmt.elseBranch);
+	}
+	void visit(Stmt.Print stmt){
+		version(LoxPrintMultiple){
+			foreach(expr; stmt.expressions)
+				resolve(expr);
+		} else {
+			resolve(stmt.expression);
+		}
+	}
+	void visit(Stmt.Return stmt){
+		if(currentFunction == FunctionType.NONE)
+			Lox.error(stmt.keyword, "Can't return from top-level code.");
+		if(stmt.value !is null){
+			if(currentFunction == FunctionType.INITIALISER)
+				Lox.error(stmt.keyword, "Can't return a value from an initializer.");
+			resolve(stmt.value);
+		}
+	}
+	void visit(Stmt.While stmt){
+		resolve(stmt.condition);
+		resolve(stmt.body);
+	}
+	void visit(Expr.Binary expr){
+		resolve(expr.left);
+		resolve(expr.right);
+	}
+	void visit(Expr.Call expr){
+		resolve(expr.callee);
+		foreach(argument; expr.arguments)
+			resolve(argument);
+	}
+	void visit(Expr.Get expr){
+		resolve(expr.object);
+	}
+	void visit(Expr.Grouping expr){
+		resolve(expr.expression);
+	}
+	void visit(Expr.Literal expr){}
+	void visit(Expr.Logical expr){
+		resolve(expr.left);
+		resolve(expr.right);
+	}
+	void visit(Expr.Set expr){
+		resolve(expr.value);
+		resolve(expr.object);
+	}
+	void visit(Expr.Super expr){
+		if(currentClass == ClassType.NONE)
+			Lox.error(expr.keyword, "Can't use 'super' outside of a class.");
+		else if (currentClass != ClassType.SUBCLASS)
+			Lox.error(expr.keyword, "Can't use 'super' in a class with no superclass.");
+		resolveLocal(expr, expr.keyword);
+	}
+	void visit(Expr.This expr){
+		if(currentClass == ClassType.NONE){
+			Lox.error(expr.keyword, "Can't use 'this' outside of a class.");
+			return;
+		}
+		resolveLocal(expr, expr.keyword);
+	}
+	void visit(Expr.Unary expr){
+		resolve(expr.right);
+	}
+}
+
diff --git a/src/jlox/scanner.d b/src/jlox/scanner.d
index 5d0a412..8da932f 100644
--- a/src/jlox/scanner.d
+++ b/src/jlox/scanner.d
@@ -6,11 +6,9 @@ import std.conv;
 import jlox.token;
 import jlox.tokentype;
 import jlox.main;
+import common.util;
 
-private bool isAlpha_(dchar c)    => c.isAlpha    || c == '_';
-private bool isAlphaNum_(dchar c) => c.isAlphaNum || c == '_';
-
-class Scanner {
+class Scanner{
 	private string source;
 	private Token[] tokens;
 	private uint start = 0;
@@ -30,7 +28,7 @@ class Scanner {
 		current++;
 		return true;
 	}
-	private void addToken(TokenType type, TValue literal = TValue.nil(tvalueNil)){
+	private void addToken(TokenType type, LoxValue literal = new LoxNil()){
 		string text = source[start .. current];
 		tokens ~= new Token(type, text, literal, line);
 	}
@@ -54,7 +52,7 @@ class Scanner {
 		}
 		advance();
 		string value = source[start + 1 .. current -1];
-		addToken(TokenType.STRING, TValue.str(value));
+		addToken(TokenType.STRING, new LoxStr(value));
 	}
 	private void number(){
 		while(peek().isDigit)
@@ -64,7 +62,7 @@ class Scanner {
 			while(peek().isDigit)
 				advance();
 		}
-		addToken(TokenType.NUMBER, TValue.dbl(source[start .. current].to!double));
+		addToken(TokenType.NUMBER, new LoxNum(source[start .. current].to!double));
 	}
 	private TokenType keywords(string word){
 		with(TokenType) switch(word){
diff --git a/src/jlox/stmt.d b/src/jlox/stmt.d
index ad701c8..64d35ae 100644
--- a/src/jlox/stmt.d
+++ b/src/jlox/stmt.d
@@ -12,6 +12,7 @@ import jlox.expr;
 abstract class Stmt{
 	interface Visitor(R){
 		R visit(Block expr);
+		R visit(Class expr);
 		R visit(Expression expr);
 		R visit(Function expr);
 		R visit(If expr);
@@ -33,6 +34,12 @@ abstract class Stmt{
 		Stmt[] statements;
 		mixin defCtorAndAccept;
 	}
+	static class Class : typeof(this){
+		Token name;
+		Expr.Variable superclass;
+		Function[] methods;
+		mixin defCtorAndAccept;
+	}
 	static class Expression : typeof(this){
 		Expr expression;
 		mixin defCtorAndAccept;
@@ -50,7 +57,10 @@ abstract class Stmt{
 		mixin defCtorAndAccept;
 	}
 	static class Print : typeof(this){
-		Expr expression;
+		version(LoxPrintMultiple)
+			Expr[] expressions;
+		else
+			Expr expression;
 		mixin defCtorAndAccept;
 	}
 	static class Return : typeof(this){
diff --git a/src/jlox/token.d b/src/jlox/token.d
index fb2c117..dcbf5a3 100644
--- a/src/jlox/token.d
+++ b/src/jlox/token.d
@@ -1,48 +1,70 @@
 module jlox.token;
 
+import std.stdio;
 import std.conv;
+import std.format : format;
 
-import taggedalgebraic;
-
+import common.util;
 import jlox.tokentype;
 import jlox.interpreter;
+import jlox.loxclass;
+import jlox.loxinstance;
+import jlox.loxfunction;
 
-interface LoxCallable{
+abstract interface LoxValue{
+	string toString() const;
+	final bool equals(LoxValue v){
+		if(this.classinfo != v.classinfo)
+			return false;
+		else if(auto s = cast(LoxStr)this)
+			return s.str == (cast(LoxStr)v).str;
+		else if(auto n = cast(LoxNum)this)
+			return n.num == (cast(LoxNum)v).num;
+		else if(auto b = cast(LoxBool)this)
+			return b.bln == (cast(LoxBool)v).bln;
+		return this == v;
+	};
+}
+interface LoxCallable : LoxValue{
 	int arity();
-	TValue call(Interpreter interpreter, TValue[] arguments);
+	LoxValue call(Interpreter interpreter, LoxValue[] arguments);
 }
-private struct Value{
-	string str;
-	double dbl;
-	bool bln;
-	LoxCallable cal;
-	struct Nil{}
-	Nil nil;
+class LoxStr : LoxValue{
+	immutable string str;
+	alias str this;
+	mixin defaultCtor;
+	override string toString() const => str;
 }
-alias TValue = TaggedUnion!Value;
-immutable tvalueNil = Value.Nil();
-string tvalueToString(TValue val){
-	final switch(val.kind){
-		case TValue.Kind.str:
-			return val.strValue;
-		case TValue.Kind.dbl:
-			return val.dblValue.to!string;
-		case TValue.Kind.bln:
-			return val.blnValue ? "true" : "false";
-		case TValue.Kind.cal:
-			return "<function>";
-		case TValue.Kind.nil:
-			return "nil";
+class LoxBool : LoxValue{
+	immutable bool bln;
+	alias bln this;
+	mixin defaultCtor;
+	override string toString() const => bln.to!string;
+}
+class LoxNum : LoxValue{
+	immutable double num;
+	alias num this;
+	mixin defaultCtor;
+	override string toString() const => num.to!string;
+	auto opBinary(string op)(const LoxNum rhs) const{
+		mixin("auto v = num", op, "rhs.num;");
+		static if(is(typeof(v) == bool))
+			return new LoxBool(v);
+		else
+			return new LoxNum(v);
 	}
 }
+class LoxNil : LoxValue{
+	override string toString() const => "<nil>";
+}
 
 class Token{
 	TokenType type;
 	string lexeme;
-	TValue literal;
+	LoxValue literal;
 	int line; 
 
-	this(TokenType type, string lexeme, TValue literal, int line) {
+	this(TokenType type, string lexeme, LoxValue literal, int line) {
 		this.type = type;
 		this.lexeme = lexeme;
 		this.literal = literal;
diff --git a/test/all.d b/test/all.d
index 5b79f0e..a7c3542 100755
--- a/test/all.d
+++ b/test/all.d
@@ -1,22 +1,56 @@
 #!/bin/env rdmd
 
+import std.stdio;
 import std.process;
+import std.concurrency;
 import std.conv;
+import std.string, std.format;
+import std.algorithm, std.range;
 
 void main(){
-	string fib(uint n){
-		string r = "";
-		double a = 0;
-		double temp;
-		for(double b = 1; a <= n; b = temp + b){
-			r ~= a.to!string ~ "\n";
-			temp = a;
-			a = b;
-		}
-		return r;
-	}
-	assert([ "./lox", "test/fib21.lox" ].execute.output == fib(6765));
-	assert([ "./lox", "test/fib10.lox" ].execute.output == fib(34));
-	assert([ "./lox", "test/closure.lox" ].execute.output == "1\n2\n");
+	"./test/ops.lox".match("1\n2\n3\n4\n5\n6\n7\ntrue\nfalse\ntrue\ntrue\nhello, world\n");
+	"./test/shortcircuit.lox".match("true\nAAAA!\nAAAA!\nAAAA?\n");
+	"./test/closure.lox".match("1\n2\n");
+	"./test/scope.lox".match("global first first second first ".replace(' ', '\n').repeat(2).join("\n"));
+	"./test/fib_for.lox".match(fib(6765));
+	"./test/fib_recursive.lox".match(fib(34));
+	"./test/fib_closure.lox".match(fib(34));
+	"./test/class.lox".match("The German chocolate cake is delicious!\n");
+	"./test/super.lox".match("Fry until golden brown.\nPipe full of custard and coat with chocolate.\nA method\n");
+
+	"./test/err/invalid_syntax.lox".shouldFail(RetVal.other);
+	"./test/err/already_defined.lox".shouldFail(RetVal.other, "Already a variable with this name");
+	"./test/err/undefined_var.lox".shouldFail(RetVal.runtime, "Undefined variable");
+	"./test/err/self_ref_vardecl.lox".shouldFail(RetVal.runtime, "Undefined variable");
+	"./test/err/global_scope_return.lox".shouldFail(RetVal.other, "Can't return from top-level code");
+	"./test/err/super_outside_class.lox".shouldFail(RetVal.other, "Can't use 'super' outside of a class");
+	"./test/err/super_without_superclass.lox".shouldFail(RetVal.other, "Can't use 'super' in a class with no superclass");
+}
+
+enum RetVal{
+	success = 0, other = 1, runtime = 2
+}
+
+string fib(uint n){
+	string r = "";
+	double a = 0;
+	double temp;
+	for(double b = 1; a <= n; b = temp + b){
+		r ~= a.to!string ~ "\n";
+		temp = a;
+		a = b;
+	}
+	return r;
+}
+auto run(string file) => [ "./lox", file ].execute;
+void match(string file, string correct){
+	auto res = file.run.output;
+	assert(res == correct, "Match %s failed\n-- Got --\n%s\n-- Expected --\n%s".format(file, res, correct));
+}
+void shouldFail(string file, int code = 1, string msg = null){
+	auto c = file.run;
+	assert(c.status == code, "Expected %s to fail with code %d but got %d".format(file, code, c.status));
+	assert(!msg || c.output.toLower.indexOf(msg.toLower) >= 0, "ShouldFail %s failed\n-- Got --\n%s\n-- Expected --\n%s".format(file, c.output, msg));
+	assert(c.output.indexOf("_Dmain") == -1, "ShouldFail %s got D exception\n%s".format(file, c.output));
 }
 
diff --git a/test/class.lox b/test/class.lox
new file mode 100644
index 0000000..87bfb6a
--- /dev/null
+++ b/test/class.lox
@@ -0,0 +1,21 @@
+
+class Cake{
+	init(goodness){
+		this.adjective = this.rate(goodness);
+	}
+	rate(goodness){
+		if(goodness)
+			return "delicious";
+		else
+			return "horrendous";
+	}
+	taste(){
+		print "The " + this.flavor + " cake is " + this.adjective + "!";
+	}
+}
+
+var cake = Cake(true);
+cake.flavor = "German chocolate";
+var t = cake.taste;
+t();
+
diff --git a/test/err/already_defined.lox b/test/err/already_defined.lox
new file mode 100644
index 0000000..6d142d4
--- /dev/null
+++ b/test/err/already_defined.lox
@@ -0,0 +1,6 @@
+
+fun bad(){
+	var a = "first";
+	var a = "second";
+}
+
diff --git a/test/err/global_scope_return.lox b/test/err/global_scope_return.lox
new file mode 100644
index 0000000..c0658c2
--- /dev/null
+++ b/test/err/global_scope_return.lox
@@ -0,0 +1,3 @@
+
+return ":)";
+
diff --git a/test/err/invalid_syntax.lox b/test/err/invalid_syntax.lox
new file mode 100644
index 0000000..24823b1
--- /dev/null
+++ b/test/err/invalid_syntax.lox
@@ -0,0 +1,3 @@
+
+foo
+
diff --git a/test/err/self_ref_vardecl.lox b/test/err/self_ref_vardecl.lox
new file mode 100644
index 0000000..e58a127
--- /dev/null
+++ b/test/err/self_ref_vardecl.lox
@@ -0,0 +1,3 @@
+
+var x = x + 1;
+
diff --git a/test/err/super_outside_class.lox b/test/err/super_outside_class.lox
new file mode 100644
index 0000000..4a14239
--- /dev/null
+++ b/test/err/super_outside_class.lox
@@ -0,0 +1,3 @@
+
+super.notEvenInAClass();
+
diff --git a/test/err/super_without_superclass.lox b/test/err/super_without_superclass.lox
new file mode 100644
index 0000000..d6b4cdc
--- /dev/null
+++ b/test/err/super_without_superclass.lox
@@ -0,0 +1,8 @@
+
+class Eclair{
+	cook(){
+		super.cook();
+		print "Pipe full of crème pâtissière.";
+	}
+}
+
diff --git a/test/err/undefined_var.lox b/test/err/undefined_var.lox
new file mode 100644
index 0000000..b3162ca
--- /dev/null
+++ b/test/err/undefined_var.lox
@@ -0,0 +1,3 @@
+
+print hello;
+
diff --git a/test/fib_closure.lox b/test/fib_closure.lox
new file mode 100644
index 0000000..42c8fe8
--- /dev/null
+++ b/test/fib_closure.lox
@@ -0,0 +1,18 @@
+
+fun fibonacci(){
+	var a = 0;
+	var b = 1;
+	fun f(){
+		var next = a;
+		a = b;
+		b = next + b;
+		return next;
+	}
+	return f;
+}
+
+var nextFibonacci = fibonacci();
+
+for(var i = 0; i < 10; i = i + 1)
+	print nextFibonacci();
+
diff --git a/test/fib21.lox b/test/fib_for.lox
similarity index 100%
rename from test/fib21.lox
rename to test/fib_for.lox
diff --git a/test/fib10.lox b/test/fib_recursive.lox
similarity index 100%
rename from test/fib10.lox
rename to test/fib_recursive.lox
diff --git a/test/ops.lox b/test/ops.lox
new file mode 100644
index 0000000..30da068
--- /dev/null
+++ b/test/ops.lox
@@ -0,0 +1,17 @@
+
+print 2 - 1;
+print 1 + 1;
+print 6 / 2;
+print 2 * 2;
+print 2 * 3 - 1;
+print 1 + 2 + 3;
+print 1 + 2 * 3;
+
+print 2 <= 3 or false;
+print 1 > 2;
+
+print 1 == 1;
+print 1 != 2;
+
+print "hello, " + "world";
+
diff --git a/test/scope.lox b/test/scope.lox
new file mode 100644
index 0000000..4b9eadc
--- /dev/null
+++ b/test/scope.lox
@@ -0,0 +1,19 @@
+
+var a = "global";
+
+fun f(){
+	print a;
+	var a = "first";
+	print a;
+	{
+		print a;
+		var a = "second";
+		print a;
+	}
+	print a;
+}
+
+f();
+print "";
+f();
+
diff --git a/test/shortcircuit.lox b/test/shortcircuit.lox
new file mode 100644
index 0000000..7e03749
--- /dev/null
+++ b/test/shortcircuit.lox
@@ -0,0 +1,12 @@
+
+fun scream(extra){
+	extra = extra or "!";
+	print "AAAA" + extra;
+}
+
+print nil or true;
+
+scream(false);
+scream(nil);
+scream("?");
+
diff --git a/test/super.lox b/test/super.lox
new file mode 100644
index 0000000..dec5f8d
--- /dev/null
+++ b/test/super.lox
@@ -0,0 +1,36 @@
+
+class Doughnut{
+	cook(){
+		print "Fry until golden brown.";
+	}
+}
+
+class BostonCream < Doughnut{
+	cook(){
+		super.cook();
+		print "Pipe full of custard and coat with chocolate.";
+	}
+}
+
+BostonCream().cook();
+
+
+class A{
+	method(){
+		print "A method";
+	}
+}
+
+class B < A{
+	method(){
+		print "B method";
+	}
+	test(){
+		super.method();
+	}
+}
+
+class C < B{}
+
+C().test();
+