diff --git a/rust/src/compiler.rs b/rust/src/compiler.rs
new file mode 100644
index 0000000..0899064
--- /dev/null
+++ b/rust/src/compiler.rs
@@ -0,0 +1,22 @@
+use crate::scanner::{Scanner, TokenKind};
+use color_eyre::eyre::Result;
+
+pub fn compile(source: &str) -> Result<()> {
+    let mut scanner = Scanner::new(source);
+
+    let mut line = None;
+    loop {
+        let token = scanner.scan()?;
+        if Some(token.line) != line {
+            print!("{:4} ", token.line);
+            line = Some(token.line);
+        } else {
+            print!("   | ");
+        }
+        println!("{:2?} '{}'", token.kind, token.value);
+
+        if token.kind == TokenKind::Eof {
+            return Ok(());
+        }
+    }
+}
diff --git a/rust/src/error.rs b/rust/src/error.rs
index 4cf7d4c..60cfbe9 100644
--- a/rust/src/error.rs
+++ b/rust/src/error.rs
@@ -1,5 +1,5 @@
 use std::io;
-use std::process::{ExitCode, Termination};
+// use std::process::{ExitCode, Termination};
 
 use thiserror::Error;
 
@@ -22,13 +22,13 @@ pub enum Error {
 // Doesn't actually work with eyre... yet? But I'm
 // willing to give up "nice" exit status codes for
 // eyre's error handling.
-impl Termination for Error {
-    fn report(self) -> ExitCode {
-        ExitCode::from(match self {
-            Error::Compile => 65,
-            Error::Runtime => 70,
-            Error::ReadFile { path, source } => 74,
-            Error::Usage => 64,
-        })
-    }
-}
+// impl Termination for Error {
+//     fn report(self) -> ExitCode {
+//         ExitCode::from(match self {
+//             Error::Compile => 65,
+//             Error::Runtime => 70,
+//             Error::ReadFile { path, source } => 74,
+//             Error::Usage => 64,
+//         })
+//     }
+// }
diff --git a/rust/src/main.rs b/rust/src/main.rs
index dd2616b..c16b643 100644
--- a/rust/src/main.rs
+++ b/rust/src/main.rs
@@ -11,7 +11,9 @@ use tracing::Level;
 use tracing_subscriber::FmtSubscriber;
 
 mod chunk;
+mod compiler;
 mod error;
+mod scanner;
 mod value;
 mod vm;
 
diff --git a/rust/src/scanner.rs b/rust/src/scanner.rs
new file mode 100644
index 0000000..c3c9a44
--- /dev/null
+++ b/rust/src/scanner.rs
@@ -0,0 +1,353 @@
+use color_eyre::eyre::Result;
+
+pub struct Scanner<'a> {
+    source: &'a [u8],
+    start: usize,
+    current: usize,
+    line: usize,
+}
+
+impl<'a> Scanner<'a> {
+    pub fn new(source: &'a str) -> Self {
+        Self {
+            source: source.as_bytes(),
+            start: 0,
+            current: 0,
+            line: 1,
+        }
+    }
+
+    pub fn scan(&mut self) -> Result<Token> {
+        self.skip_whitespace();
+
+        self.start = self.current;
+
+        if self.is_at_end() {
+            return self.make_token(TokenKind::Eof);
+        }
+
+        let c = self.advance();
+        if is_alpha(c) {
+            return self.identifier();
+        }
+        if c.is_digit(10) {
+            return self.number();
+        }
+
+        return match c {
+            '(' => self.make_token(TokenKind::LeftParen),
+            ')' => self.make_token(TokenKind::RightParen),
+            '{' => self.make_token(TokenKind::LeftBrace),
+            '}' => self.make_token(TokenKind::RightBrace),
+            ';' => self.make_token(TokenKind::Semicolon),
+            ',' => self.make_token(TokenKind::Comma),
+            '.' => self.make_token(TokenKind::Dot),
+            '-' => self.make_token(TokenKind::Minus),
+            '+' => self.make_token(TokenKind::Plus),
+            '/' => self.make_token(TokenKind::Slash),
+            '*' => self.make_token(TokenKind::Star),
+            '!' => {
+                if self.is_match('=') {
+                    self.make_token(TokenKind::BangEqual)
+                } else {
+                    self.make_token(TokenKind::Bang)
+                }
+            }
+            '=' => {
+                if self.is_match('=') {
+                    self.make_token(TokenKind::EqualEqual)
+                } else {
+                    self.make_token(TokenKind::Equal)
+                }
+            }
+            '<' => {
+                if self.is_match('=') {
+                    self.make_token(TokenKind::LessEqual)
+                } else {
+                    self.make_token(TokenKind::Less)
+                }
+            }
+            '>' => {
+                if self.is_match('=') {
+                    self.make_token(TokenKind::GreaterEqual)
+                } else {
+                    self.make_token(TokenKind::Greater)
+                }
+            }
+            '"' => self.string(),
+            _ => self.error_token("Unexpected character."),
+        };
+    }
+
+    fn is_at_end(&self) -> bool {
+        self.source[self.current] == 0
+    }
+
+    fn make_token(&self, kind: TokenKind) -> Result<Token> {
+        Ok(Token {
+            kind,
+            value: std::str::from_utf8(&self.source[self.start..self.current])?,
+            line: self.line,
+        })
+    }
+
+    fn error_token(&self, message: &'static str) -> Result<Token> {
+        Ok(Token {
+            kind: TokenKind::Error,
+            value: message,
+            line: self.line,
+        })
+    }
+
+    fn advance(&mut self) -> char {
+        self.current += 1;
+        self.source[self.current - 1] as char
+    }
+
+    fn is_match(&mut self, expected: char) -> bool {
+        if self.is_at_end() {
+            return false;
+        }
+
+        if self.source[self.current] as char != expected {
+            return false;
+        }
+
+        self.current += 1;
+        true
+    }
+
+    fn skip_whitespace(&mut self) {
+        loop {
+            let c = self.peek();
+            match c {
+                ' ' | '\r' | '\t' => {
+                    self.advance();
+                    break;
+                }
+                '\n' => {
+                    self.line += 1;
+                    self.advance();
+                    break;
+                }
+                '/' => {
+                    if self.peek_next() == '/' {
+                        while self.peek() != '\n' && !self.is_at_end() {
+                            self.advance();
+                        }
+                    } else {
+                        return;
+                    }
+                }
+                _ => {
+                    return;
+                }
+            }
+        }
+    }
+
+    fn peek(&self) -> char {
+        self.source[self.current] as char
+    }
+
+    fn peek_next(&mut self) -> char {
+        if self.is_at_end() {
+            0 as char
+        } else {
+            self.source[self.current + 1] as char
+        }
+    }
+
+    fn string(&mut self) -> Result<Token> {
+        while self.peek() != '"' && !self.is_at_end() {
+            if self.peek() == '\n' {
+                self.line += 1;
+            }
+            self.advance();
+        }
+
+        if self.is_at_end() {
+            return self.error_token("Unterminated string.");
+        }
+
+        self.advance();
+        self.make_token(TokenKind::String)
+    }
+
+    fn number(&mut self) -> Result<Token> {
+        while self.peek().is_digit(10) {
+            self.advance();
+        }
+
+        if self.peek() == '.' && self.peek_next().is_digit(10) {
+            self.advance();
+
+            while self.peek().is_digit(10) {
+                self.advance();
+            }
+        }
+
+        self.make_token(TokenKind::Number)
+    }
+
+    fn identifier(&mut self) -> Result<Token> {
+        while is_alpha(self.peek()) || self.peek().is_digit(10) {
+            self.advance();
+        }
+
+        self.make_token(self.identifier_type())
+    }
+
+    fn identifier_type(&self) -> TokenKind {
+        match self.source[self.start] as char {
+            'a' => self.check_keyword(1, "nd", TokenKind::And),
+            'c' => self.check_keyword(1, "lass", TokenKind::Class),
+            'e' => self.check_keyword(1, "lse", TokenKind::Else),
+            'i' => self.check_keyword(1, "f", TokenKind::If),
+            'n' => self.check_keyword(1, "il", TokenKind::Nil),
+            'o' => self.check_keyword(1, "r", TokenKind::Or),
+            'p' => self.check_keyword(1, "rint", TokenKind::Print),
+            'r' => self.check_keyword(1, "eturn", TokenKind::Return),
+            's' => self.check_keyword(1, "uper", TokenKind::Super),
+            'v' => self.check_keyword(1, "ar", TokenKind::Var),
+            'w' => self.check_keyword(1, "hile", TokenKind::While),
+            'f' => {
+                if self.current - self.start > 1 {
+                    match self.source[self.start + 1] as char {
+                        'a' => self.check_keyword(2, "lse", TokenKind::False),
+                        'o' => self.check_keyword(2, "r", TokenKind::For),
+                        'u' => self.check_keyword(2, "n", TokenKind::Fun),
+                        _ => TokenKind::Identifier
+                    }
+                } else {
+                    TokenKind::Identifier
+                }
+            }
+            't' => {
+                if self.current - self.start > 1 {
+                    match self.source[self.start + 1] as char {
+                        'h' => self.check_keyword(2, "is", TokenKind::This),
+                        'r' => self.check_keyword(2, "ue", TokenKind::True),
+                        _ => TokenKind::Identifier
+                    }
+                } else {
+                    TokenKind::Identifier
+                }
+            }
+            _ => TokenKind::Identifier,
+        }
+    }
+
+    fn check_keyword(&self, start: usize, rest: &str, kind: TokenKind) -> TokenKind {
+        // Do I have an off-by-one error here?
+        if &self.source[self.start + start..self.current] == rest.as_bytes() {
+            kind
+        } else {
+            TokenKind::Identifier
+        }
+    }
+}
+
+fn is_alpha(c: char) -> bool {
+    c.is_ascii_alphabetic() || c == '_'
+}
+
+pub struct Token<'a> {
+    pub kind: TokenKind,
+    pub value: &'a str,
+    pub line: usize,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum TokenKind {
+    // Single-character tokens.
+    LeftParen,
+    RightParen,
+    LeftBrace,
+    RightBrace,
+    Comma,
+    Dot,
+    Minus,
+    Plus,
+    Semicolon,
+    Slash,
+    Star,
+    // One or two character tokens.
+    Bang,
+    BangEqual,
+    Equal,
+    EqualEqual,
+    Greater,
+    GreaterEqual,
+    Less,
+    LessEqual,
+    // Literals.
+    Identifier,
+    String,
+    Number,
+    // Keywords.
+    And,
+    Class,
+    Else,
+    False,
+    For,
+    Fun,
+    If,
+    Nil,
+    Or,
+    Print,
+    Return,
+    Super,
+    This,
+    True,
+    Var,
+    While,
+    //
+    Error,
+    Eof,
+}
+
+#[cfg(test)]
+mod tests {
+    // Note this useful idiom: importing names from outer (for mod tests) scope.
+    use super::*;
+
+    #[test]
+    fn test_scan() {
+        assert_scan_token("(", TokenKind::LeftParen);
+
+        assert_scan_token("!", TokenKind::Bang);
+        assert_scan_token("!=", TokenKind::BangEqual);
+        assert_scan_token("!a", TokenKind::Bang);
+
+        assert_scan_token("a", TokenKind::Identifier);
+        assert_scan_token("_a", TokenKind::Identifier);
+        assert_scan_token("a1", TokenKind::Identifier);
+
+        assert_scan_token("\"foo\"", TokenKind::String);
+
+        assert_scan_token("1a", TokenKind::Number);
+        assert_scan_token("1.1", TokenKind::Number);
+
+        assert_scan_token("and", TokenKind::And);
+        assert_scan_token("andy", TokenKind::Identifier);
+
+        assert_scan_token("@", TokenKind::Error);
+        assert_scan_token("", TokenKind::Eof);
+    }
+
+    #[test]
+    fn test_whitespace() {
+        assert_scan_token(" foo", TokenKind::Identifier);
+        assert_scan_token("\tfoo", TokenKind::Identifier);
+        assert_scan_token("//   \n", TokenKind::Eof);
+    }
+
+    fn assert_scan_token(source: &str, kind: TokenKind) {
+        let mut s = source.to_string();
+        s.push(0 as char);
+        let mut scanner = Scanner::new(&s);
+        let token = scanner.scan().unwrap();
+        assert_eq!(token.kind, kind);
+    }
+}
diff --git a/rust/src/vm.rs b/rust/src/vm.rs
index e70d147..a4de50d 100644
--- a/rust/src/vm.rs
+++ b/rust/src/vm.rs
@@ -2,10 +2,9 @@ use std::ops::{Add, Div, Mul, Sub};
 
 use color_eyre::eyre::Result;
 
-use crate::{
-    chunk::{Chunk, DisassembledInstruction, OpCode},
-    value::Value,
-};
+use crate::chunk::{Chunk, DisassembledInstruction, OpCode};
+use crate::compiler::compile;
+use crate::value::Value;
 use tracing::debug;
 
 pub struct VM {
@@ -16,6 +15,11 @@ pub struct VM {
 }
 
 impl VM {
+    pub fn interpret(source: &str) -> Result<()> {
+        compile(source);
+        Ok(())
+    }
+
     pub fn new(chunk: Chunk) -> Self {
         Self {
             chunk,