Finished up to and including chapter 16

Cargo.lock

@@ -2,6 +2,21 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "aho-corasick"
+version = "0.7.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc936419f96fa211c1b9166887b38e5e40b19958e5b895be7c1f93adec7071ac"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -124,6 +139,12 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
 [[package]]
 name = "libc"
 version = "0.2.139"
@@ -136,6 +157,32 @@ version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f051f77a7c8e6957c0696eac88f26b0117e54f52d3fc682ab19397a8812846a4"
 
+[[package]]
+name = "memchr"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+
+[[package]]
+name = "num-derive"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "876a53fff98e03a936a674b29568b0e605f06b29372c2489ff4de23f1949743d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "578ede34cf02f8924ab9447f50c28075b4d3e5b269972345e7e0372b38c6cdcd"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.17.0"
@@ -247,6 +294,23 @@ version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
 
+[[package]]
+name = "regex"
+version = "1.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48aaa5748ba571fb95cd2c85c09f629215d3a6ece942baa100950af03a34f733"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.6.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "456c603be3e8d448b072f410900c09faf164fbce2d480456f50eea6e25f9c848"
+
 [[package]]
 name = "rlox2"
 version = "0.1.0"
@@ -254,6 +318,7 @@ dependencies = [
  "clap",
  "rlox2-frontend",
  "rlox2-interpreter",
+ "rlox2-vm",
 ]
 
 [[package]]
@@ -271,9 +336,29 @@ version = "0.1.0"
 dependencies = [
  "itertools",
  "rlox2-frontend",
+ "rustc-hash",
  "thiserror",
 ]
 
+[[package]]
+name = "rlox2-vm"
+version = "0.1.0"
+dependencies = [
+ "itertools",
+ "lazy_static",
+ "num-derive",
+ "num-traits",
+ "regex",
+ "rlox2-frontend",
+ "thiserror",
+]
+
+[[package]]
+name = "rustc-hash"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08d43f7aa6b08d49f382cde6a7982047c3426db949b1424bc4b7ec9ae12c6ce2"
+
 [[package]]
 name = "rustix"
 version = "0.36.7"

Cargo.toml

@@ -8,7 +8,7 @@ name = "rlox"
 path = "src/main.rs"
 
 [workspace]
-members = ["frontend", "interpreter"]
+members = ["frontend", "interpreter", "vm"]
 
 [dependencies.rlox2-frontend]
 path = "frontend"
@@ -16,5 +16,8 @@ path = "frontend"
 [dependencies.rlox2-interpreter]
 path = "interpreter"
 
+[dependencies.rlox2-vm]
+path = "vm"
+
 [dependencies]
 clap = { version = "4.1.4", features = ["derive"] }

frontend/src/parser/expr.rs

@@ -55,9 +55,9 @@ pub enum Expr {
         value: Box<Expr>,
     },
     Function {
-        name: Box<String>,
+        name: String,
-        param_names: Box<Vec<String>>,
+        param_names: Vec<String>,
-        closure_vars: Box<Vec<(String, usize)>>,
+        closure_vars: Vec<(String, usize)>,
         body: Box<Stmt>,
     },
     Class {
@@ -137,10 +137,11 @@ impl Expr {
     }
 
     pub fn function(name: String, param_names: Vec<String>, body: Stmt) -> Self {
-        let name = Box::new(name);
+        // let name = Box::new(name);
-        let param_names = Box::new(param_names);
+        // let param_names = Box::new(param_names);
         #[allow(clippy::box_default)]
-        let closure_vars = Box::new(Vec::new());
+        // let closure_vars = Box::new(Vec::new());
+        let closure_vars = Vec::new();
         let body = Box::new(body);
         Self::Function {
             name,
@@ -258,7 +259,7 @@ impl Display for UnaryOp {
 
 /*====================================================================================================================*/
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 #[rustfmt::skip]
 pub enum BinaryOp {
     // arithmetic
@@ -289,7 +290,7 @@ impl Display for BinaryOp {
     }
 }
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum LogicalOp {
     Or,
     And,

interpreter/Cargo.toml

@@ -11,3 +11,4 @@ path = "../frontend"
 [dependencies]
 thiserror = "1.0.38"
 itertools = "0.10.5"
+rustc-hash = "1.1.0"

interpreter/src/class.rs

@@ -1,8 +1,8 @@
-use std::collections::HashMap;
 use std::fmt::Display;
 use std::rc::Rc;
 
 use rlox2_frontend::parser::{Expr, Stmt};
+use rustc_hash::FxHashMap;
 
 use crate::{LoxFunction, LoxReference, Value};
 
@@ -12,12 +12,16 @@ pub struct LoxClass {
 
     name: String,
 
-    methods: HashMap<String, Value>,
+    methods: FxHashMap<String, Value>,
 }
 
 /// Representation of a class in Lox. Always behind an Rc to ensure uniqueness. Should never be handled raw.
 impl LoxClass {
-    pub fn new(name: impl Into<String>, methods: HashMap<String, Value>, superclass: Option<Rc<LoxClass>>) -> Rc<Self> {
+    pub fn new(
+        name: impl Into<String>,
+        methods: FxHashMap<String, Value>,
+        superclass: Option<Rc<LoxClass>>,
+    ) -> Rc<Self> {
         let name = name.into();
         let mut methods = methods;
 
@@ -42,7 +46,7 @@ impl LoxClass {
         }
 
         if let Some(ref superclass) = superclass {
-            let mut new_methods: HashMap<String, Value> = HashMap::new();
+            let mut new_methods: FxHashMap<String, Value> = FxHashMap::default();
 
             // Rc<LoxFunction> is immutable, so we need to drain, change, and replace
             for (name, value) in methods {

interpreter/src/environment.rs

@@ -1,48 +1,94 @@
-use std::collections::HashMap;
 use std::fmt::Display;
 use std::io::{Read, Write};
 
+use rustc_hash::FxHashMap;
+
 use crate::error::RuntimeError;
 
 use super::value::HeapedValue;
 use super::{Runtime, Value};
 
-pub type Scope = HashMap<String, HeapedValue>;
+pub type Scope = FxHashMap<String, HeapedValue>;
 
 #[derive(Debug)]
 pub struct Environment<'a> {
-    local_scopes: Vec<Scope>,
+    scope_stack: Vec<Scope>,
+    scope_top: usize,
 
     runtime: &'a mut Runtime,
+
+    arg_stack: Vec<Value>,
 }
 
 impl<'a> Environment<'a> {
     pub fn new(runtime: &'a mut Runtime) -> Self {
         Environment {
-            // globals: HashMap::new(),
+            scope_stack: Vec::new(),
-            // frames: vec![Frame::new_global()],
+            scope_top: 0,
-            local_scopes: Vec::new(),
 
             runtime,
+
+            arg_stack: Vec::new(),
         }
     }
 
-    pub fn globals(&self) -> &HashMap<String, Value> {
+    pub fn push_arg(&mut self, arg: Value) {
+        self.arg_stack.push(arg);
+    }
+
+    pub fn num_args(&self) -> usize {
+        self.arg_stack.len()
+    }
+
+    pub fn collect_args(&mut self) -> Vec<Value> {
+        std::mem::take(&mut self.arg_stack)
+    }
+
+    pub fn globals(&self) -> &FxHashMap<String, Value> {
         self.runtime.globals()
     }
 
+    pub fn scopes(&self) -> &[Scope] {
+        &self.scope_stack[..self.scope_top]
+    }
+
+    pub fn scopes_mut(&mut self) -> &mut [Scope] {
+        &mut self.scope_stack[..self.scope_top]
+    }
+
+    pub fn has_scope(&self) -> bool {
+        !self.scope_stack.is_empty()
+    }
+
+    pub fn current_scope(&self) -> &Scope {
+        &self.scope_stack[self.scope_top - 1]
+    }
+
+    pub fn current_scope_mut(&mut self) -> &mut Scope {
+        &mut self.scope_stack[self.scope_top - 1]
+    }
+
     pub fn enter_scope(&mut self) {
         // self.current_frame_mut().enter_scope();
-        self.local_scopes.push(Scope::new());
+        // self.local_scopes.push(Scope::new());
+
+        if self.scope_top == self.scope_stack.len() {
+            self.scope_stack.push(Scope::default());
+        } else {
+            self.scope_stack[self.scope_top].clear();
+        }
+
+        self.scope_top += 1;
     }
 
     pub fn exit_scope(&mut self) {
         // self.current_frame_mut().exit_scope();
-        self.local_scopes.pop().expect("Tried to pop global scope");
+        // self.local_scopes.pop().expect("Tried to pop global scope");
+        self.scope_top -= 1;
     }
 
     pub fn insert_closure(&mut self, closure: Scope) {
-        let scope = self.local_scopes.last_mut().unwrap();
+        let scope = self.current_scope_mut();
 
         for (name, value) in closure {
             scope.insert(name, value);
@@ -54,9 +100,10 @@ impl<'a> Environment<'a> {
     }
 
     pub fn get_local(&self, name: &str, level: usize) -> Result<Value, RuntimeError> {
-        let len = self.local_scopes.len();
+        let len = self.scopes().len();
+
         if level < len {
-            if let Some(heap_value) = self.local_scopes[len - level - 1].get(name) {
+            if let Some(heap_value) = self.scopes()[len - level - 1].get(name) {
                 return Ok(heap_value.get_clone());
             }
         }
@@ -66,9 +113,9 @@ impl<'a> Environment<'a> {
     }
 
     pub fn define(&mut self, name: impl Into<String>, value: Value) {
-        if let Some(scope) = self.local_scopes.last_mut() {
+        if self.has_scope() {
             let name = name.into();
-            scope.insert(name, HeapedValue::new(value));
+            self.current_scope_mut().insert(name, HeapedValue::new(value));
         } else {
             self.runtime.define_global(name, value)
         }
@@ -79,7 +126,7 @@ impl<'a> Environment<'a> {
     }
 
     pub fn assign(&mut self, name: &str, value: Value, level: usize) -> Result<(), RuntimeError> {
-        if let Some(scope) = self.local_scopes.iter_mut().rev().nth(level) {
+        if let Some(scope) = self.scopes_mut().iter_mut().rev().nth(level) {
             if let Some(heap_value) = scope.get_mut(name) {
                 heap_value.replace(value);
                 return Ok(());
@@ -99,7 +146,7 @@ impl<'a> Environment<'a> {
     } */
 
     pub fn collect_closure(&self, closure_vars: &[(String, usize)]) -> Scope {
-        let mut closure_scope = Scope::new();
+        let mut closure_scope = Scope::default();
 
         for (name, level) in closure_vars {
             // special injected variables
@@ -108,7 +155,7 @@ impl<'a> Environment<'a> {
             }
 
             let heap_value = self
-                .local_scopes
+                .scopes()
                 .iter()
                 .rev()
                 .nth(*level)
@@ -130,7 +177,7 @@ impl Display for Environment<'_> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         write!(f, "{}", self.runtime)?;
 
-        for (level, scope) in self.local_scopes.iter().enumerate() {
+        for (level, scope) in self.scopes().iter().enumerate() {
             write!(f, "\nScope {level}:")?;
 
             for (name, value) in scope.iter() {

interpreter/src/interpret.rs

@@ -1,7 +1,7 @@
-use std::collections::HashMap;
 use std::rc::Rc;
 
 use rlox2_frontend::parser::{BinaryOp, Expr, Literal, LogicalOp, Stmt, UnaryOp};
+use rustc_hash::FxHashMap;
 
 use crate::error::RuntimeError;
 use crate::function::LoxExternFunction;
@@ -29,8 +29,7 @@ trait Eval {
 }
 
 impl Eval for Literal {
-    fn eval(&self, env: &mut Environment) -> EvalResult<Value> {
+    fn eval(&self, _env: &mut Environment) -> EvalResult<Value> {
-        let _ = env;
         match self {
             Literal::String(s) => Ok(Value::String(Rc::clone(s))),
             Literal::Number(num) => Ok(Value::Number(*num)),
@@ -57,57 +56,60 @@ impl Eval for Expr {
             Expr::Binary { left, op, right } => {
                 use Value::{Bool, Number, String};
 
+                let op = *op;
+
                 let left = left.eval(env)?;
                 let right = right.eval(env)?;
 
-                match (left, *op, right) {
+                if op == BinaryOp::Equal {
-                    (Number(left), BinaryOp::Add, Number(right)) => Ok(Number(left + right)),
+                    return Ok(Bool(left == right));
-                    (Number(left), BinaryOp::Subtract, Number(right)) => Ok(Number(left - right)),
-                    (Number(left), BinaryOp::Multiply, Number(right)) => Ok(Number(left * right)),
-                    (Number(left), BinaryOp::Divide, Number(right)) => {
-                        if right == 0.0 {
-                            return Err(RuntimeError::DivisionByZero);
-                        }
-                        Ok(Number(left / right))
                 }
 
-                    (String(left), BinaryOp::Add, String(right)) => {
+                if op == BinaryOp::NotEqual {
+                    return Ok(Bool(left != right));
+                }
+
+                match (left, right) {
+                    (Number(left), Number(right)) => match op {
+                        BinaryOp::Add => Ok(Number(left + right)),
+                        BinaryOp::Subtract => Ok(Number(left - right)),
+                        BinaryOp::Multiply => Ok(Number(left * right)),
+                        BinaryOp::Divide => Ok(Number(left / right)),
+                        BinaryOp::Less => Ok(Bool(left < right)),
+                        BinaryOp::LessEqual => Ok(Bool(left <= right)),
+                        BinaryOp::Greater => Ok(Bool(left > right)),
+                        BinaryOp::GreaterEqual => Ok(Bool(left >= right)),
+                        _ => unreachable!(),
+                    },
+                    (String(left), String(right)) => match op {
+                        BinaryOp::Add => {
                             let mut s = std::string::String::with_capacity(left.capacity() + right.capacity());
                             s += &left;
                             s += &right;
                             Ok(String(Rc::new(s)))
                         }
-
+                        BinaryOp::Less => Ok(Bool(left < right)),
-                    (left, BinaryOp::Equal, right) => Ok(Bool(left == right)),
+                        BinaryOp::LessEqual => Ok(Bool(left <= right)),
-                    (left, BinaryOp::NotEqual, right) => Ok(Bool(left != right)),
+                        BinaryOp::Greater => Ok(Bool(left > right)),
-
+                        BinaryOp::GreaterEqual => Ok(Bool(left >= right)),
-                    (Number(left), BinaryOp::Less, Number(right)) => Ok(Bool(left < right)),
+                        BinaryOp::Equal | BinaryOp::NotEqual => unreachable!(),
-                    (Number(left), BinaryOp::LessEqual, Number(right)) => Ok(Bool(left <= right)),
+                        _ => Err(RuntimeError::BinaryOpInvalidArguments {
-                    (Number(left), BinaryOp::Greater, Number(right)) => Ok(Bool(left > right)),
+                            left: String(left),
-                    (Number(left), BinaryOp::GreaterEqual, Number(right)) => Ok(Bool(left >= right)),
+                            op,
-
+                            right: String(right),
-                    (String(left), BinaryOp::Less, String(right)) => Ok(Bool(left < right)),
+                        }),
-                    (String(left), BinaryOp::LessEqual, String(right)) => Ok(Bool(left <= right)),
+                    },
-                    (String(left), BinaryOp::Greater, String(right)) => Ok(Bool(left > right)),
+                    (left, right) => Err(RuntimeError::BinaryOpInvalidArguments { left, op, right }),
-                    (String(left), BinaryOp::GreaterEqual, String(right)) => Ok(Bool(left >= right)),
-
-                    (left, op, right) => Err(RuntimeError::BinaryOpInvalidArguments { left, op, right }),
                 }
             }
             Expr::Logical { left, op, right } => {
                 let left = left.eval(env)?;
-                match op {
+
-                    LogicalOp::Or => {
+                // shortcircuit
-                        if left.is_truthy() {
+                if *op == LogicalOp::Or && left.is_truthy() || *op == LogicalOp::And && !left.is_truthy() {
                     return Ok(left);
                 }
-                    }
+
-                    LogicalOp::And => {
-                        if !left.is_truthy() {
-                            return Ok(left);
-                        }
-                    }
-                }
                 let right = right.eval(env)?;
                 Ok(right)
             }
@@ -127,15 +129,20 @@ impl Eval for Expr {
             }
             Expr::Call { callee, args } => {
                 let callee = callee.eval(env)?;
-                let args = args
+                /* let args = args
                 .iter()
                 .map(|arg| arg.eval(env))
-                    .collect::<EvalResult<Vec<Value>>>()?;
+                .collect::<EvalResult<Vec<Value>>>()?; */
+
+                for arg in args {
+                    let arg = arg.eval(env)?;
+                    env.push_arg(arg);
+                }
 
                 match callee {
-                    Value::Function(fun) => LoxFunction::call(fun, args, env),
+                    Value::Function(fun) => call_fun(fun, env),
-                    Value::ExternFunction(ext_fun) => ext_fun.call(args, env),
+                    Value::ExternFunction(ext_fun) => call_extfun(ext_fun, env),
-                    Value::Class(class) => LoxClass::call(class, args, env),
+                    Value::Class(class) => call_class(class, env),
                     _ => Err(RuntimeError::NotCallable { callee }),
                 }
             }
@@ -169,9 +176,9 @@ impl Eval for Expr {
                 closure_vars,
                 body,
             } => Ok(Value::function(LoxFunction::new(
-                name.as_ref(),
+                name,
                 env.collect_closure(closure_vars),
-                param_names.as_ref().clone(),
+                param_names.clone(),
                 body.as_ref().clone(),
             ))),
             Expr::Class {
@@ -186,7 +193,7 @@ impl Eval for Expr {
                     None => None,
                 };
 
-                let mut methods: HashMap<String, Value> = HashMap::new();
+                let mut methods: FxHashMap<String, Value> = FxHashMap::default();
 
                 // this is the scope "this" will get injected in
                 env.enter_scope();
@@ -285,8 +292,9 @@ impl Eval for Stmt {
 
 /*====================================================================================================================*/
 
-impl LoxFunction {
+pub fn call_fun(fun: Rc<LoxFunction>, env: &mut Environment) -> EvalResult<Value> {
-    pub fn call(fun: Rc<LoxFunction>, args: Vec<Value>, env: &mut Environment) -> EvalResult<Value> {
+    let args = env.collect_args();
+
     if args.len() != fun.arity() {
         return Err(RuntimeError::WrongArity {
             name: fun.name().to_owned(),
@@ -314,31 +322,31 @@ impl LoxFunction {
     env.exit_scope();
 
     ret_val
-    }
 }
 
-impl LoxExternFunction {
+pub fn call_extfun(ext_fun: Rc<LoxExternFunction>, env: &mut Environment) -> EvalResult<Value> {
-    pub fn call(&self, args: Vec<Value>, env: &mut Environment) -> EvalResult<Value> {
+    let args = env.collect_args();
-        if args.len() != self.arity() {
+
+    if args.len() != ext_fun.arity() {
         return Err(RuntimeError::WrongArity {
-                name: self.name().to_owned(),
+            name: ext_fun.name().to_owned(),
-                arity: self.arity(),
+            arity: ext_fun.arity(),
             given: args.len(),
         });
     }
 
-        (self.closure())(args, env)
+    (ext_fun.closure())(args, env)
-    }
 }
 
-impl LoxClass {
+// has to take class as an argument instead of as self to leave it behind its Rc
-    // has to take class as an argument instead of as self to leave it behind its Rc
+pub fn call_class(class: Rc<LoxClass>, env: &mut Environment) -> EvalResult<Value> {
-    pub fn call(class: Rc<LoxClass>, args: Vec<Value>, env: &mut Environment) -> EvalResult<Value> {
+    // let args = env.collect_args();
-        if args.len() != class.arity() {
+
+    if env.num_args() != class.arity() {
         return Err(RuntimeError::WrongArity {
             name: class.name().to_owned(),
             arity: class.arity(),
-                given: args.len(),
+            given: env.num_args(),
         });
     }
 
@@ -347,9 +355,8 @@ impl LoxClass {
     // object.init(args, env)?;
 
     if let Some(Value::Function(method)) = object.get("init") {
-            LoxFunction::call(method, args, env)?;
+        call_fun(method, env)?;
     }
 
     Ok(Value::Object(object))
-    }
 }

interpreter/src/lib.rs

@@ -15,6 +15,6 @@ pub use error::{LoxError, RuntimeError};
 pub use function::LoxFunction;
 pub use object::LoxReference;
 pub use resolver::{resolve, ResolverError};
-pub use run::{run_file, run_repl};
+pub use run::{run, run_repl};
 pub use runtime::Runtime;
 pub use value::Value;

interpreter/src/object.rs

@@ -1,8 +1,9 @@
 use std::cell::UnsafeCell;
-use std::collections::HashMap;
 use std::fmt::Display;
 use std::rc::Rc;
 
+use rustc_hash::FxHashMap;
+
 use crate::{LoxClass, Value};
 
 /// This struct is private, since *nothing* is supposed to be handling an object directly,
@@ -11,14 +12,14 @@ use crate::{LoxClass, Value};
 struct LoxObject {
     class: Rc<LoxClass>,
 
-    attrs: HashMap<String, Value>,
+    attrs: FxHashMap<String, Value>,
 }
 
 impl LoxObject {
     fn new(class: Rc<LoxClass>) -> Self {
         LoxObject {
             class,
-            attrs: HashMap::new(),
+            attrs: FxHashMap::default(),
         }
     }
 

interpreter/src/resolver/resolve.rs

@@ -1,13 +1,12 @@
-use std::collections::HashMap;
-
 use rlox2_frontend::parser::{Expr, Stmt};
+use rustc_hash::FxHashMap;
 
 use crate::Runtime;
 use crate::{LoxError, ResolverError};
 
 /*====================================================================================================================*/
 
-type ResolverScope = HashMap<String, ResolveStatus>;
+type ResolverScope = FxHashMap<String, ResolveStatus>;
 type ResolverFrame = Vec<ResolverScope>;
 
 /*====================================================================================================================*/
@@ -36,12 +35,12 @@ struct Resolver {
     // local_scopes: Vec<ResolverScope>,
     frames: Vec<ResolverFrame>,
 
-    closure_vars: HashMap<String, usize>,
+    closure_vars: FxHashMap<String, usize>,
 }
 
 impl Resolver {
     fn new(global_names: impl Iterator<Item = String>) -> Self {
-        let mut global_scope = ResolverScope::new();
+        let mut global_scope = ResolverScope::default();
 
         for name in global_names {
             global_scope.insert(name, ResolveStatus::Defined);
@@ -50,7 +49,7 @@ impl Resolver {
         Resolver {
             global_scope,
             frames: vec![ResolverFrame::new()],
-            closure_vars: HashMap::new(),
+            closure_vars: FxHashMap::default(),
         }
     }
 
@@ -63,7 +62,7 @@ impl Resolver {
     }
 
     fn enter_scope(&mut self) {
-        self.local_scopes_mut().push(ResolverScope::new());
+        self.local_scopes_mut().push(ResolverScope::default());
     }
 
     fn exit_scope(&mut self) {
@@ -73,7 +72,7 @@ impl Resolver {
     }
 
     fn push_frame(&mut self) {
-        self.frames.push(vec![ResolverScope::new()]);
+        self.frames.push(vec![ResolverScope::default()]);
     }
 
     fn pop_frame(&mut self) {

interpreter/src/run.rs

@@ -9,32 +9,6 @@ use crate::resolver::resolve;
 
 use super::Runtime;
 
-pub fn run_file(runtime: &mut Runtime, script_path: &str) {
-    let source_code = std::fs::read_to_string(script_path).unwrap_or_else(|err| {
-        eprintln!("Reading script file {script_path} failed: {err}");
-        std::process::exit(66);
-    });
-
-    /* if let Err(err) = run(&source_code) {
-        eprintln!("{}", err);
-        std::process::exit(65);
-    } */
-
-    match run(&source_code, runtime) {
-        Ok(()) => {}
-        Err(err) => {
-            eprintln!("{err}");
-            match err {
-                LoxError::LexerError { .. } | LoxError::ParserError { .. } | LoxError::ResolverError { .. } => {
-                    std::process::exit(65)
-                }
-                LoxError::RuntimeError { .. } => std::process::exit(70),
-                LoxError::Exit { exit_code } => std::process::exit(exit_code),
-            }
-        }
-    }
-}
-
 pub fn run_repl(runtime: &mut Runtime) {
     let stdin = std::io::stdin();
 
@@ -87,8 +61,8 @@ pub fn run_repl(runtime: &mut Runtime) {
     }
 }
 
-fn run(code_string: &str, runtime: &mut Runtime) -> Result<(), LoxError> {
+pub fn run(source: &str, runtime: &mut Runtime) -> Result<(), LoxError> {
-    let tokens: Vec<Token> = scan_tokens(code_string)?;
+    let tokens: Vec<Token> = scan_tokens(source)?;
 
     /* let token_str = tokens
         .iter()

interpreter/src/runtime.rs

@@ -1,14 +1,15 @@
-use std::collections::HashMap;
 use std::fmt::Display;
 use std::io::{stdin, stdout, Read, Write};
 
+use rustc_hash::FxHashMap;
+
 use crate::error::RuntimeError;
 
 use super::lox_std::init_std;
 use super::Value;
 
 pub struct Runtime {
-    globals: HashMap<String, Value>,
+    globals: FxHashMap<String, Value>,
 
     in_stream: Box<dyn std::io::BufRead>,
     out_stream: Box<dyn std::io::Write>,
@@ -18,7 +19,7 @@ impl Runtime {
     pub fn new(in_stream: Box<dyn std::io::Read>, out_stream: Box<dyn std::io::Write>) -> Self {
         let in_stream = Box::new(std::io::BufReader::new(in_stream));
         let mut runtime = Runtime {
-            globals: HashMap::new(),
+            globals: FxHashMap::default(),
             in_stream,
             out_stream,
         };
@@ -28,7 +29,7 @@ impl Runtime {
         runtime
     }
 
-    pub fn globals(&self) -> &HashMap<String, Value> {
+    pub fn globals(&self) -> &FxHashMap<String, Value> {
         &self.globals
     }
 

src/main.rs

@@ -1,5 +1,4 @@
 use clap::{ArgAction, Parser};
-use rlox2_interpreter::{run_file, run_repl, Runtime};
 
 #[derive(Parser, Debug)]
 struct CliArgs {
@@ -8,24 +7,73 @@ struct CliArgs {
 
     #[arg(short, action = ArgAction::SetTrue)]
     interactive: bool,
+
+    #[arg(long, action = ArgAction::SetTrue)]
+    vm: bool,
 }
 
+/*
+let source_code = std::fs::read_to_string(script_path).unwrap_or_else(|err| {
+    eprintln!("Reading script file {script_path} failed: {err}");
+    std::process::exit(66);
+}); */
+
 fn main() {
-    interpreter_main();
-}
-
-pub fn interpreter_main() {
     let cli_args = CliArgs::parse();
 
-    let mut runtime = Runtime::default();
+    if cli_args.vm {
+        use rlox2_vm::InterpretError;
+
+        let mut vm = rlox2_vm::VM::default();
 
         if let Some(file_name) = cli_args.file_name {
-        run_file(&mut runtime, &file_name);
+            let source = std::fs::read_to_string(&file_name).unwrap_or_else(|err| {
+                eprintln!("Reading script file {file_name} failed: {err}");
+                std::process::exit(66);
+            });
 
-        if cli_args.interactive {
+            if let Err(err) = rlox2_vm::run(&source, &mut vm) {
-            run_repl(&mut runtime);
+                eprintln!("{err}");
+                match err {
+                    InterpretError::LexerError { .. } | InterpretError::CompileError { .. } => std::process::exit(65),
+                    InterpretError::RuntimeError { .. } => std::process::exit(70),
+                    InterpretError::Exit { exit_code } => std::process::exit(exit_code),
                 }
+            }
+
+            if !cli_args.interactive {
+                return;
+            }
+        }
+
+        rlox2_vm::run_repl(&mut vm);
     } else {
-        run_repl(&mut runtime);
+        use rlox2_interpreter::LoxError;
+
+        let mut runtime = rlox2_interpreter::Runtime::default();
+
+        if let Some(file_name) = cli_args.file_name {
+            let source = std::fs::read_to_string(&file_name).unwrap_or_else(|err| {
+                eprintln!("Reading script file {file_name} failed: {err}");
+                std::process::exit(66);
+            });
+
+            if let Err(err) = rlox2_interpreter::run(&source, &mut runtime) {
+                eprintln!("{err}");
+                match err {
+                    LoxError::LexerError { .. } | LoxError::ParserError { .. } | LoxError::ResolverError { .. } => {
+                        std::process::exit(65)
+                    }
+                    LoxError::RuntimeError { .. } => std::process::exit(70),
+                    LoxError::Exit { exit_code } => std::process::exit(exit_code),
+                }
+            }
+
+            if !cli_args.interactive {
+                return;
+            }
+        }
+
+        rlox2_interpreter::run_repl(&mut runtime);
     }
 }

vm/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "rlox2-vm"
+version = "0.1.0"
+edition = "2021"
+
+
+[dependencies.rlox2-frontend]
+path = "../frontend"
+
+
+[dependencies]
+itertools = "0.10.5"
+lazy_static = "1.4.0"
+num-derive = "0.3.3"
+num-traits = "0.2.15"
+regex = "1.7.1"
+thiserror = "1.0.38"

vm/src/chunk.rs

@@ -0,0 +1,68 @@
+use crate::debug::ChunkDebugInfo;
+use crate::{Opcode, Value};
+
+#[derive(Debug, Default)]
+pub struct Chunk {
+    code: Vec<u8>,
+
+    constants: Vec<Value>,
+
+    debug_info: Option<ChunkDebugInfo>,
+}
+
+impl Chunk {
+    pub fn new() -> Self {
+        Chunk {
+            code: Vec::new(),
+            constants: Vec::new(),
+            debug_info: Some(ChunkDebugInfo::new()),
+        }
+    }
+
+    pub fn code(&self) -> &[u8] {
+        &self.code
+    }
+
+    pub fn debug_info(&self) -> Option<&ChunkDebugInfo> {
+        self.debug_info.as_ref()
+    }
+
+    pub fn debug_info_mut(&mut self) -> Option<&mut ChunkDebugInfo> {
+        self.debug_info.as_mut()
+    }
+
+    pub fn write_byte<T>(&mut self, byte: T, line: u32)
+    where
+        T: TryInto<u8> + std::fmt::Debug,
+        <T as std::convert::TryInto<u8>>::Error: std::fmt::Debug,
+    {
+        let byte = byte.try_into().unwrap();
+
+        self.code.push(byte);
+
+        if let Some(ref mut debug_info) = self.debug_info {
+            debug_info.write_line(line, self.code.len() - 1);
+        }
+    }
+
+    pub fn write_bytes(&mut self, bytes: &[u8], line: u32) {
+        for byte in bytes {
+            self.write_byte(*byte, line);
+        }
+    }
+
+    pub fn write_opcode(&mut self, opcode: Opcode, line: u32) {
+        let byte = opcode as u8;
+        self.write_byte(byte, line);
+    }
+
+    pub fn add_constant(&mut self, value: Value) -> usize {
+        self.constants.push(value);
+
+        self.constants.len() - 1
+    }
+
+    pub fn get_constant(&self, offset: usize) -> &Value {
+        &self.constants[offset]
+    }
+}

vm/src/compile.rs

@@ -0,0 +1,6 @@
+use itertools::Itertools;
+use rlox2_frontend::lexer::Token;
+
+pub fn compile(tokens: Vec<Token>) {
+    println!("{}", tokens.iter().map(|token| token.to_string()).join(" "));
+}

vm/src/debug.rs

@@ -0,0 +1,76 @@
+#[derive(Debug)]
+struct LineInfo {
+    start_offset: usize,
+    line: u32,
+}
+
+#[derive(Debug, Default)]
+pub struct ChunkDebugInfo {
+    line_infos: Vec<LineInfo>,
+}
+
+impl ChunkDebugInfo {
+    pub fn new() -> Self {
+        ChunkDebugInfo { line_infos: Vec::new() }
+    }
+
+    pub fn write_line(&mut self, line: u32, offset: usize) {
+        let line_info = || LineInfo {
+            start_offset: offset,
+            line,
+        };
+
+        if self.line_infos.is_empty() {
+            self.line_infos.push(line_info())
+        }
+
+        match line.cmp(&self.line_infos.last().unwrap().line) {
+            // assert increasing line numbers
+            std::cmp::Ordering::Less => panic!(
+                "Tried to write_byte for line {line}, but line {} is already written",
+                self.line_infos.last().unwrap().line
+            ),
+            // line same as for last byte -> do nothing
+            std::cmp::Ordering::Equal => {}
+            // line greater than for last byte -> insert new line marker at current position
+            std::cmp::Ordering::Greater => self.line_infos.push(line_info()),
+        }
+    }
+
+    pub fn line_number(&self, offset: usize) -> u32 {
+        /* if self.line_infos.len() > 2 && offset < self.line_infos[1].start_offset {
+            assert!(offset >= self.line_infos[0].start_offset);
+
+            return self.line_infos[0].line;
+        }
+
+        let mut low = 0; // will be max { line_offset : line_offset < offset }
+        let mut high = self.line_infos.len() - 1; // will be min { line_offset : line_offset >= offset }
+
+        // bisect line_numbers
+        while high > low + 1 {
+            // as high >= low + 2, never high or low
+            let mid = (low + high) / 2;
+
+            match offset.cmp(&self.line_infos[mid].start_offset) {
+                std::cmp::Ordering::Less => high = mid,
+                std::cmp::Ordering::Equal => return self.line_infos[mid].line,
+                std::cmp::Ordering::Greater => low = mid,
+            }
+        }
+
+        self.line_infos[high].line */
+
+        // special case: all start_offsets are <= than offset:
+        // need to manually return the last line number as slice::partition_point doesn't like that
+        if self.line_infos.last().unwrap().start_offset <= offset {
+            return self.line_infos.last().unwrap().line;
+        }
+
+        let idx = self
+            .line_infos
+            .partition_point(|line_info| line_info.start_offset < offset);
+
+        self.line_infos[idx].line
+    }
+}

vm/src/disassemble.rs

@@ -0,0 +1,61 @@
+use num_traits::FromPrimitive;
+
+use crate::Chunk;
+use crate::Opcode;
+
+impl Chunk {
+    pub fn disassemble(&self, name: &str) {
+        println!("==== begin {name} ====\n");
+
+        let mut offset = 0;
+
+        while offset < self.code().len() {
+            offset = self.disassemble_instruction(offset)
+        }
+
+        println!("\n====  end {name}  ====");
+    }
+
+    pub fn disassemble_instruction(&self, offset: usize) -> usize {
+        use Opcode::*;
+
+        let mut offset = offset;
+
+        print!("{offset:04} ");
+
+        if let Some(debug_info) = self.debug_info() {
+            if offset == 0 || debug_info.line_number(offset) != debug_info.line_number(offset - 1) {
+                let line = debug_info.line_number(offset);
+                print!("{line:4} ");
+            } else {
+                print!("   | ");
+            };
+        }
+
+        let opcode: Opcode = FromPrimitive::from_u8(self.code()[offset]).unwrap();
+        offset += 1;
+
+        print!("{opcode:<16} ");
+
+        match opcode {
+            LoadConst => {
+                let constant_idx = self.code()[offset];
+                let value = self.get_constant(constant_idx as usize);
+                print!("{constant_idx:4} '{value}'");
+                offset += 1;
+            }
+            LoadConstLong => {
+                let bytes = &self.code()[offset..offset + 3];
+                let constant_idx = u32::from_le_bytes([bytes[0], bytes[1], bytes[2], 0]);
+                let value = self.get_constant(constant_idx as usize);
+                print!("{constant_idx:4} '{value}'");
+                offset += 3;
+            }
+            Add | Subtract | Multiply | Divide | Negate | Return => {}
+        }
+
+        println!();
+
+        offset
+    }
+}

vm/src/error.rs

@@ -0,0 +1,58 @@
+use itertools::Itertools;
+use rlox2_frontend::lexer::LexerError;
+use thiserror::Error;
+
+use crate::{Opcode, Value};
+
+#[derive(Error, Debug)]
+pub enum CompileError {}
+
+#[derive(Error, Debug)]
+pub enum RuntimeError {
+    #[error("Opcopde {opcode} had invalid operand {operand}")]
+    UnaryInvalidOperand { opcode: Opcode, operand: Value },
+    #[error("Opcopde {opcode} had invalid operands {left} and {right}")]
+    BinaryInvalidOperand { opcode: Opcode, left: Value, right: Value },
+    #[error("Division by zero")]
+    DivisionByZero,
+}
+
+#[derive(Error, Debug)]
+pub enum InterpretError {
+    #[error("{0}", format_multiple_errors(inner))]
+    LexerError { inner: Vec<LexerError> },
+    #[error("{inner}")]
+    CompileError { inner: CompileError },
+    #[error("{inner}")]
+    RuntimeError { inner: RuntimeError },
+    #[error("Called exit() with exit code {exit_code}")]
+    Exit { exit_code: i32 },
+}
+
+impl From<Vec<LexerError>> for InterpretError {
+    fn from(lexer_errs: Vec<LexerError>) -> Self {
+        InterpretError::LexerError { inner: lexer_errs }
+    }
+}
+
+impl From<CompileError> for InterpretError {
+    fn from(compile_err: CompileError) -> Self {
+        InterpretError::CompileError { inner: compile_err }
+    }
+}
+
+impl From<RuntimeError> for InterpretError {
+    fn from(runtime_err: RuntimeError) -> Self {
+        InterpretError::RuntimeError { inner: runtime_err }
+    }
+}
+
+fn format_multiple_errors(errs: &Vec<impl std::error::Error>) -> String {
+    let msg = if errs.len() == 1 {
+        errs[0].to_string()
+    } else {
+        errs.iter().map(|err| err.to_string()).join("\n")
+    };
+
+    msg
+}

vm/src/lib.rs

@@ -0,0 +1,17 @@
+mod chunk;
+mod compile;
+mod debug;
+mod disassemble;
+mod error;
+mod opcode;
+mod run;
+mod value;
+mod vm;
+
+pub use chunk::Chunk;
+pub use compile::compile;
+pub use error::InterpretError;
+pub use opcode::Opcode;
+pub use run::{run, run_repl};
+pub use value::Value;
+pub use vm::VM;

vm/src/opcode.rs

@@ -0,0 +1,35 @@
+use std::fmt::Display;
+
+use itertools::Itertools;
+use lazy_static::lazy_static;
+use num_derive::FromPrimitive;
+use regex::Regex;
+
+lazy_static! {
+    static ref CAMEL_CASE_REGEX: Regex = Regex::new(r"[A-Z][a-z]*").unwrap();
+}
+
+#[repr(u8)]
+#[derive(Debug, FromPrimitive, Clone, Copy)]
+#[allow(non_camel_case_types)] // hack so Constant_Long will be printed as CONSTANT_LONG rather than CONSTANTLONG
+pub enum Opcode {
+    LoadConst,
+    LoadConstLong,
+    Add,
+    Subtract,
+    Multiply,
+    Divide,
+    Negate,
+    Return,
+}
+
+impl Display for Opcode {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let name = CAMEL_CASE_REGEX
+            .captures_iter(&format!("{self:?}"))
+            .map(|cap| cap[0].to_ascii_uppercase())
+            .join("_");
+
+        f.pad(&name)
+    }
+}

vm/src/run.rs

@@ -0,0 +1,97 @@
+use std::io::Write;
+
+use rlox2_frontend::lexer::{scan_tokens, Token};
+
+use crate::{compile, InterpretError, VM};
+
+/* pub fn vm_main() {
+    let mut chunk = Chunk::new();
+
+    let constant1 = chunk.add_constant(Value::Number(1.2));
+    let constant2 = chunk.add_constant(Value::Number(3.4));
+    let constant3 = chunk.add_constant(Value::Number(5.6));
+
+    chunk.write_opcode(Opcode::LoadConst, 123);
+    chunk.write_byte(constant1, 123);
+
+    chunk.write_opcode(Opcode::LoadConst, 123);
+    chunk.write_byte(constant2, 123);
+
+    chunk.write_opcode(Opcode::Add, 123);
+
+    chunk.write_opcode(Opcode::LoadConst, 124);
+    chunk.write_byte(constant3, 124);
+
+    chunk.write_opcode(Opcode::Divide, 124);
+    chunk.write_opcode(Opcode::Negate, 124);
+
+    chunk.write_opcode(Opcode::Return, 125);
+
+    println!();
+    chunk.disassemble("test chunk");
+    println!();
+
+    let mut vm = VM::new();
+
+    vm.interpret(&chunk).unwrap();
+} */
+
+pub fn run_repl(vm: &mut VM) {
+    let stdin = std::io::stdin();
+
+    loop {
+        let mut input_buf = String::new();
+
+        print!("> ");
+        std::io::stdout().flush().unwrap();
+
+        'inner: loop {
+            stdin.read_line(&mut input_buf).unwrap_or_else(|err| {
+                eprintln!("Could not read from stdin: {err}");
+                std::process::exit(66);
+            });
+
+            let num_open_braces = (input_buf.matches('{').count() as i64) - (input_buf.matches('}').count() as i64);
+            let num_open_parens = (input_buf.matches('(').count() as i64) - (input_buf.matches(')').count() as i64);
+            let num_open_brackets = (input_buf.matches('[').count() as i64) - (input_buf.matches(']').count() as i64);
+
+            // all braces/parens/brackets closed => break
+            if num_open_braces == 0 && num_open_parens == 0 && num_open_brackets == 0 {
+                break 'inner;
+            }
+
+            // any braces/parens/brackets more closing than opening => break (will be parse error)
+            if num_open_braces < 0 || num_open_parens < 0 || num_open_brackets < 0 {
+                break 'inner;
+            }
+
+            print!("< ");
+
+            // let indentation = "  ".repeat((num_open_braces + num_open_brackets + num_open_parens) as usize);
+
+            // print!("{indentation}");
+
+            std::io::stdout().flush().unwrap();
+        }
+
+        let input_buf = input_buf.trim();
+
+        if input_buf.is_empty() || input_buf == "exit" || input_buf == "quit" {
+            std::process::exit(0);
+        }
+
+        match run(input_buf, vm) {
+            Ok(()) => {}
+            Err(InterpretError::Exit { exit_code }) => std::process::exit(exit_code),
+            Err(err) => eprintln!("{err}"),
+        }
+    }
+}
+
+pub fn run(source: &str, _vm: &mut VM) -> Result<(), InterpretError> {
+    let tokens: Vec<Token> = scan_tokens(source)?;
+
+    compile(tokens);
+
+    Ok(())
+}

vm/src/value.rs

@@ -0,0 +1,22 @@
+use std::fmt::Display;
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Value {
+    Nil,
+    Number(f64),
+}
+
+impl Default for Value {
+    fn default() -> Self {
+        Value::Nil
+    }
+}
+
+impl Display for Value {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Value::Nil => write!(f, "nil"),
+            Value::Number(num) => write!(f, "{num}"),
+        }
+    }
+}

vm/src/vm.rs

@@ -0,0 +1,225 @@
+use std::ptr;
+
+use num_traits::FromPrimitive;
+
+use crate::error::RuntimeError;
+use crate::{Chunk, Opcode};
+use crate::{InterpretError, Value};
+
+/*====================================================================================================================*/
+
+const STACK_MAX: usize = 256;
+const DEBUG_TRACE_EXECUTION: bool = true;
+
+/*====================================================================================================================*/
+
+#[derive(Debug)]
+pub struct VM {
+    chunk_ptr: *const Chunk,
+
+    ip: *const u8,
+
+    stack: [Value; STACK_MAX],
+    stack_top: *mut Value,
+}
+
+/* macro_rules! debug_println {
+    ($($arg:tt)*) => {
+        if cfg!(debug_assertions) {
+            println!($($arg)*);
+        }
+    };
+} */
+
+impl VM {
+    pub fn new() -> Self {
+        const NIL: Value = Value::Nil;
+        let stack = [NIL; STACK_MAX];
+
+        let mut vm = VM {
+            chunk_ptr: ptr::null(),
+            ip: ptr::null(),
+            stack,
+            stack_top: ptr::null_mut(),
+        };
+
+        vm.stack_top = vm.stack.as_mut_ptr();
+
+        vm
+    }
+
+    unsafe fn chunk(&self) -> &Chunk {
+        &*self.chunk_ptr
+    }
+
+    unsafe fn offset(&self) -> usize {
+        let offset = self.ip.offset_from(self.chunk().code().as_ptr());
+
+        debug_assert!(offset >= 0);
+
+        offset as usize
+    }
+
+    unsafe fn stack_len(&self) -> usize {
+        let offset = self.stack_top.offset_from(self.stack.as_ptr());
+
+        debug_assert!(offset >= 0);
+
+        offset as usize
+    }
+
+    unsafe fn push_value(&mut self, value: Value) {
+        // ptr::write(self.stack_top, value);
+        debug_assert!(self.stack_len() < STACK_MAX);
+        let old_value = std::mem::replace(&mut *self.stack_top, value);
+        debug_assert_eq!(old_value, Value::Nil);
+        self.stack_top = self.stack_top.add(1);
+    }
+
+    unsafe fn pop_value(&mut self) -> Value {
+        assert!(self.stack_len() < STACK_MAX);
+
+        self.stack_top = self.stack_top.sub(1);
+        // ptr::read(self.stack_top)
+        std::mem::take(&mut *self.stack_top)
+    }
+
+    pub fn interpret(&mut self, chunk: &Chunk) -> Result<(), InterpretError> {
+        self.chunk_ptr = chunk;
+        self.ip = chunk.code().as_ptr();
+
+        unsafe { self.run()? }
+
+        Ok(())
+    }
+
+    unsafe fn read_byte(&mut self) -> u8 {
+        debug_assert!(self.offset() < self.chunk().code().len());
+
+        let byte = *self.ip;
+        self.ip = self.ip.add(1);
+        byte
+    }
+
+    unsafe fn read_constant(&mut self) -> &Value {
+        let constant_idx = self.read_byte() as usize;
+
+        self.chunk().get_constant(constant_idx)
+    }
+
+    unsafe fn read_constant_long(&mut self) -> &Value {
+        let bytes = [self.read_byte(), self.read_byte(), self.read_byte(), 0];
+        let constant_idx = u32::from_le_bytes(bytes) as usize;
+
+        self.chunk().get_constant(constant_idx)
+    }
+
+    unsafe fn run(&mut self) -> Result<(), RuntimeError> {
+        loop {
+            if DEBUG_TRACE_EXECUTION {
+                println!();
+                self.print_stack();
+                self.chunk().disassemble_instruction(self.offset());
+                println!();
+            }
+
+            let opcode: Opcode = FromPrimitive::from_u8(self.read_byte()).unwrap();
+
+            match opcode {
+                Opcode::LoadConst => {
+                    let value = self.read_constant().clone();
+                    println!("Constant: {value}");
+                    self.push_value(value);
+                }
+                Opcode::LoadConstLong => {
+                    let value = self.read_constant_long().clone();
+                    println!("LongConstant: {value}");
+                    self.push_value(value);
+                }
+
+                Opcode::Add => {
+                    let right = self.pop_value();
+                    let left = self.pop_value();
+                    match (left, right) {
+                        (Value::Number(left), Value::Number(right)) => {
+                            self.push_value(Value::Number(left + right));
+                        }
+                        // (Value::String(left), Value::String(right)) => todo!(),
+                        (left, right) => return Err(RuntimeError::BinaryInvalidOperand { opcode, left, right }),
+                    }
+                }
+                Opcode::Subtract => {
+                    let right = self.pop_value();
+                    let left = self.pop_value();
+                    match (left, right) {
+                        (Value::Number(left), Value::Number(right)) => {
+                            self.push_value(Value::Number(left - right));
+                        }
+                        (left, right) => return Err(RuntimeError::BinaryInvalidOperand { opcode, left, right }),
+                    }
+                }
+                Opcode::Multiply => {
+                    let right = self.pop_value();
+                    let left = self.pop_value();
+                    match (left, right) {
+                        (Value::Number(left), Value::Number(right)) => {
+                            self.push_value(Value::Number(left * right));
+                        }
+                        (left, right) => return Err(RuntimeError::BinaryInvalidOperand { opcode, left, right }),
+                    }
+                }
+                Opcode::Divide => {
+                    let right = self.pop_value();
+                    let left = self.pop_value();
+                    match (left, right) {
+                        (Value::Number(left), Value::Number(right)) => {
+                            if right == 0.0 {
+                                return Err(RuntimeError::DivisionByZero);
+                            }
+                            self.push_value(Value::Number(left / right));
+                        }
+                        (left, right) => return Err(RuntimeError::BinaryInvalidOperand { opcode, left, right }),
+                    }
+                }
+                Opcode::Negate => {
+                    let value = self.pop_value();
+                    println!("Negate: {value}");
+                    if let Value::Number(num) = value {
+                        self.push_value(Value::Number(-num));
+                    } else {
+                        return Err(RuntimeError::UnaryInvalidOperand { opcode, operand: value });
+                    }
+                }
+                Opcode::Return => {
+                    let value = self.pop_value();
+                    debug_assert_eq!(self.stack_len(), 0);
+                    println!("Return: {value}");
+                    return Ok(());
+                }
+            }
+        }
+    }
+
+    unsafe fn print_stack(&self) {
+        /* let s = self.stack[0..self.stack_len()]
+            .iter()
+            .map(|value| value.to_string())
+            .join(", ");
+
+        print!("{s}"); */
+
+        print!("Stack:    ");
+
+        for value in self.stack[0..self.stack_len()].iter() {
+            print!("[ {value} ]");
+        }
+
+        println!()
+    }
+}
+
+impl Default for VM {
+    fn default() -> Self {
+        VM::new()
+    }
+}