diff --git a/src/clox/compiler.d b/src/clox/compiler.d
new file mode 100644
index 0000000..c1df16b
--- /dev/null
+++ b/src/clox/compiler.d
@@ -0,0 +1,9 @@
+module clox.compiler;
+
+import std.stdio;
+
+import clox.scanner;
+
+void compile(string source) @nogc nothrow {
+}
+
diff --git a/src/clox/main.d b/src/clox/main.d
index f5dd3be..44ec26d 100644
--- a/src/clox/main.d
+++ b/src/clox/main.d
@@ -1,38 +1,46 @@
 module clox.main;
 
 import std.stdio;
+import std.file;
 
 import clox.chunk;
 import clox.dbg;
 import clox.vm;
 
-int main(string[] argv){
-	Chunk chunk;
+extern(C) int isatty(int);
 
-	ubyte constant = chunk.addConstant(1.2);
-	chunk.write(OpCode.Constant);
-	chunk.write(constant);
-
-	constant = chunk.addConstant(3.4);
-	chunk.write(OpCode.Constant);
-	chunk.write(constant);
-
-	chunk.write(OpCode.Add);
-
-	constant = chunk.addConstant(5.6);
-	chunk.write(OpCode.Constant);
-	chunk.write(constant);
-
-	chunk.write(OpCode.Divide);
-
-	chunk.write(OpCode.Negate);
-
-	chunk.write(OpCode.Return);
-
-	VM vm = VM(0);
-	vm.interpret(&chunk);
-
-
-	return 0;
+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("> ");
+			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/scanner.d b/src/clox/scanner.d
new file mode 100644
index 0000000..1d95000
--- /dev/null
+++ b/src/clox/scanner.d
@@ -0,0 +1,153 @@
+module clox.scanner;
+
+import std.stdio;
+import std.ascii;
+
+import common.util;
+
+struct Token{
+	enum Type : ubyte {
+		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,
+		Error, EOF // Special
+	}
+	Type type;
+	int line;
+	string lexeme;
+	static Token error(string msg) => Token(Token.Type.Error, 0, msg);
+}
+
+struct Scanner{
+	string start;
+	string current;
+	int line = 1;
+	this(string source){
+		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];
+		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;
+			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 '" ~ c ~ "'.");
+	}
+}
+
diff --git a/src/clox/vm.d b/src/clox/vm.d
index b9c9cfe..151ec6d 100644
--- a/src/clox/vm.d
+++ b/src/clox/vm.d
@@ -6,6 +6,7 @@ import clox.chunk;
 import clox.value;
 import clox.dbg;
 import clox.util;
+import clox.compiler;
 
 enum stackMax = 256;
 
@@ -13,10 +14,14 @@ struct VM{
 	const(ubyte)* ip;
 	Stack!(Value, stackMax) stack;
 	Chunk* chunk;
-	enum InterpretResult{ Ok, CompileError, RunetimeError }
+	enum InterpretResult{ Ok, CompileError, RuntimeError }
 	this(int _) @nogc nothrow {
 		stack = typeof(stack)(0);
 	}
+	InterpretResult interpret(string source) @nogc nothrow {
+		compile(source);
+		return InterpretResult.Ok;
+	}
 	InterpretResult interpret(Chunk* chunk) @nogc nothrow {
 		this.chunk = chunk;
 		ip = &chunk.code[0];
diff --git a/src/common/util.d b/src/common/util.d
index f8dc60d..0efa053 100644
--- a/src/common/util.d
+++ b/src/common/util.d
@@ -7,3 +7,7 @@ template defaultCtor(){
 	}
 }
 
+import std.ascii : isAlpha, isAlphaNum;
+bool isAlpha_(dchar c)    => c.isAlpha    || c == '_';
+bool isAlphaNum_(dchar c) => c.isAlphaNum || c == '_';
+
diff --git a/src/jlox/scanner.d b/src/jlox/scanner.d
index 8e78a08..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;