finished resolver (chapter 11) and started classes (chapter 12)

interpreter/src/class.rs

@@ -0,0 +1,19 @@
+use std::fmt::Display;
+
+#[derive(Debug)]
+pub struct LoxClass {
+    name: String,
+}
+
+impl LoxClass {
+    pub fn new(name: impl Into<String>) -> Self {
+        let name = name.into();
+        LoxClass { name }
+    }
+}
+
+impl Display for LoxClass {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "<class {}>", self.name)
+    }
+}

interpreter/src/environment.rs

@@ -0,0 +1,209 @@
+use std::collections::HashMap;
+use std::fmt::Display;
+use std::io::{Read, Write};
+
+use crate::error::RuntimeError;
+
+use super::value::HeapedValue;
+use super::{Runtime, Value};
+
+pub type Scope = HashMap<String, HeapedValue>;
+
+#[derive(Debug)]
+pub struct Environment<'a> {
+    local_scopes: Vec<Scope>,
+
+    runtime: &'a mut Runtime,
+}
+
+impl<'a> Environment<'a> {
+    pub fn new(runtime: &'a mut Runtime) -> Self {
+        Environment {
+            // globals: HashMap::new(),
+            // frames: vec![Frame::new_global()],
+            local_scopes: Vec::new(),
+
+            runtime,
+        }
+    }
+
+    pub fn globals(&self) -> &HashMap<String, Value> {
+        self.runtime.globals()
+    }
+
+    pub fn enter_scope(&mut self) {
+        // self.current_frame_mut().enter_scope();
+        self.local_scopes.push(Scope::new());
+    }
+
+    pub fn push_scope(&mut self, scope: Scope) {
+        self.local_scopes.push(scope);
+    }
+
+    pub fn exit_scope(&mut self) {
+        // self.current_frame_mut().exit_scope();
+        self.local_scopes.pop().expect("Tried to pop global scope");
+    }
+
+    pub fn get_global(&self, name: &str) -> Result<Value, RuntimeError> {
+        self.runtime.get_global(name)
+    }
+
+    pub fn get_local(&self, name: &str, level: usize) -> Result<Value, RuntimeError> {
+        if let Some(scope) = self.local_scopes.iter().rev().nth(level) {
+            if let Some(heap_value) = scope.get(name) {
+                return Ok(heap_value.get_clone());
+            }
+        }
+
+        // DEBUG
+        println!("Name {name} not defined at level {level}");
+        println!("{self}");
+
+        Err(RuntimeError::NameNotDefined { name: name.to_owned() })
+        // self.runtime.get_global(name)
+    }
+
+    pub fn define(&mut self, name: impl Into<String>, value: Value) {
+        if let Some(scope) = self.local_scopes.last_mut() {
+            let name = name.into();
+            scope.insert(name, HeapedValue::new(value));
+        } else {
+            self.runtime.define_global(name, value)
+        }
+    }
+
+    pub fn assign_global(&mut self, name: &str, value: Value) -> Result<(), RuntimeError> {
+        self.runtime.assign_global(name, value)
+    }
+
+    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(heap_value) = scope.get_mut(name) {
+                heap_value.replace(value);
+                return Ok(());
+            }
+        }
+
+        Err(RuntimeError::NameNotDefined { name: name.to_owned() })
+        // self.runtime.assign_global(name, value)
+    }
+
+    /* pub fn push_frame(&mut self, base_scope: Scope) {
+        self.frames.push(Frame::new(base_scope));
+    }
+
+    pub fn pop_frame(&mut self) {
+        self.frames.pop().expect("Tried to pop global frame");
+    } */
+
+    pub fn collect_closure(&self, closure_vars: &[(String, usize)]) -> Scope {
+        let mut closure_scope = Scope::new();
+
+        for (name, level) in closure_vars {
+            let heap_value = self
+                .local_scopes
+                .iter()
+                .rev()
+                .nth(*level)
+                .unwrap()
+                .get(name)
+                .unwrap()
+                .clone();
+
+            let name = name.to_owned();
+
+            closure_scope.insert(name, heap_value);
+        }
+
+        closure_scope
+    }
+}
+
+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() {
+            write!(f, "\nScope {level}:")?;
+
+            for (name, value) in scope.iter() {
+                write!(f, "\n\t{name} = {value}")?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl Read for Environment<'_> {
+    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
+        self.runtime.read(buf)
+    }
+}
+
+impl Write for Environment<'_> {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        self.runtime.write(buf)
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        self.runtime.flush()
+    }
+}
+
+/*====================================================================================================================*/
+
+/* struct Frame {
+    scopes: Vec<Scope>,
+}
+
+impl Frame {
+    fn new(base_scope: Scope) -> Self {
+        Frame {
+            scopes: vec![base_scope],
+        }
+    }
+
+    fn new_global() -> Self {
+        Frame { scopes: Vec::new() }
+    }
+
+    fn enter_scope(&mut self) {
+        self.scopes.push(Scope::new());
+    }
+
+    fn exit_scope(&mut self) {
+        self.scopes.pop().expect("Tried to exit scope, but no scope to exit");
+    }
+
+    fn get(&self, name: &str) -> Option<Value> {
+        for scope in self.scopes.iter().rev() {
+            if let Some(heap_value) = scope.get(name) {
+                return Some(heap_value.get_clone());
+            }
+        }
+
+        None
+    }
+
+    fn try_define(&mut self, name: impl Into<String> + Borrow<str>, value: Value) -> Result<(), Value> {
+        if let Some(scope) = self.scopes.last_mut() {
+            scope.insert(name.into(), HeapValue::new(value));
+            Ok(())
+        } else {
+            Err(value)
+        }
+    }
+
+    fn try_assign(&mut self, name: &str, value: Value) -> Result<(), Value> {
+        for scope in self.scopes.iter_mut().rev() {
+            if let Some(heap_value) = scope.get_mut(name) {
+                heap_value.replace(value);
+                return Ok(());
+            }
+        }
+
+        Err(value)
+    }
+} */

interpreter/src/error.rs

@@ -0,0 +1,85 @@
+use itertools::Itertools;
+use rlox2_frontend::lexer::LexerError;
+use rlox2_frontend::parser::{BinaryOp, ParserError, UnaryOp};
+use thiserror::Error;
+
+use crate::ResolverError;
+use crate::Value;
+
+#[derive(Error, Debug)]
+pub enum RuntimeError {
+    #[error("Unary operator {op} had invalid argument {arg}")]
+    UnaryOpInvalidArgument { op: UnaryOp, arg: Value },
+    #[error("Binary operator {op} had invalid arguments {left} and {right}")]
+    BinaryOpInvalidArguments { left: Value, op: BinaryOp, right: Value },
+    #[error("Division by zero")]
+    DivisionByZero,
+    #[error("Name {name} is not defined")]
+    NameNotDefined { name: String },
+    #[error("Global {name} is not defined")]
+    GlobalNotDefined { name: String },
+    #[error("{callee} is not callable")]
+    NotCallable { callee: Value },
+    #[error("{name}() takes {arity} args, but {given} were given.")]
+    WrongArity { name: String, arity: usize, given: usize },
+    #[error("Extern function call to {name} failed: {msg}")]
+    ExtFunCallFailed { name: String, msg: String },
+    #[error("Uncaught break statement")]
+    Break,
+    #[error("Uncaught return statement")]
+    Return { value: Value },
+    #[error("Exit with exit code {exit_code}")]
+    Exit { exit_code: i32 },
+}
+
+#[derive(Error, Debug)]
+#[allow(clippy::enum_variant_names)]
+pub enum LoxError {
+    #[error("{0}", format_multiple_errors(inner))]
+    LexerError { inner: Vec<LexerError> },
+    #[error("{0}", format_multiple_errors(inner))]
+    ParserError { inner: Vec<ParserError> },
+    #[error("{inner}")]
+    ResolverError { inner: ResolverError },
+    #[error("{inner}")]
+    RuntimeError { inner: RuntimeError },
+    #[error("Called exit() with exit code {exit_code}")]
+    Exit { exit_code: i32 },
+}
+
+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
+}
+
+impl From<Vec<LexerError>> for LoxError {
+    fn from(lexer_errs: Vec<LexerError>) -> Self {
+        LoxError::LexerError { inner: lexer_errs }
+    }
+}
+
+impl From<Vec<ParserError>> for LoxError {
+    fn from(parser_errs: Vec<ParserError>) -> Self {
+        LoxError::ParserError { inner: parser_errs }
+    }
+}
+
+impl From<ResolverError> for LoxError {
+    fn from(resolver_err: ResolverError) -> Self {
+        LoxError::ResolverError { inner: resolver_err }
+    }
+}
+
+impl From<RuntimeError> for LoxError {
+    fn from(runtime_err: RuntimeError) -> Self {
+        match runtime_err {
+            RuntimeError::Exit { exit_code } => LoxError::Exit { exit_code },
+            _ => LoxError::RuntimeError { inner: runtime_err },
+        }
+    }
+}

interpreter/src/function.rs

@@ -0,0 +1,104 @@
+use std::fmt::{Debug, Display};
+
+use rlox2_frontend::parser::Stmt;
+
+use super::environment::{Environment, Scope};
+use super::interpret::EvalResult;
+use super::{Runtime, Value};
+
+#[derive(Debug, Clone)]
+pub struct LoxFunction {
+    name: String,
+    closure: Scope,
+    param_names: Vec<String>,
+    body: Box<Stmt>,
+}
+
+impl LoxFunction {
+    pub fn new(name: impl Into<String>, closure: Scope, param_names: Vec<String>, body: Stmt) -> Self {
+        let name = name.into();
+        let body = Box::new(body);
+        LoxFunction {
+            name,
+            closure,
+            param_names,
+            body,
+        }
+    }
+
+    pub fn arity(&self) -> usize {
+        self.param_names.len()
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn closure(&self) -> &Scope {
+        &self.closure
+    }
+
+    pub fn param_names(&self) -> impl Iterator<Item = &String> {
+        self.param_names.iter()
+    }
+
+    pub fn body(&self) -> &Stmt {
+        &self.body
+    }
+}
+
+impl Display for LoxFunction {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "<fun {}>", self.name)
+    }
+}
+
+/*====================================================================================================================*/
+
+pub type ExternFunClosure = fn(Vec<Value>, &mut Environment) -> EvalResult<Value>;
+
+#[derive(Clone)]
+pub struct LoxExternFunction {
+    name: String,
+
+    closure: ExternFunClosure,
+}
+
+impl LoxExternFunction {
+    pub fn new(name: impl Into<String>, closure: ExternFunClosure) -> Self {
+        let name = name.into();
+
+        LoxExternFunction { name, closure }
+    }
+
+    pub fn register(self, env: &mut Runtime) {
+        let name = self.name.clone();
+        let fun = Value::extern_function(self);
+        env.define_global(name, fun);
+    }
+
+    pub fn call(&self, args: Vec<Value>, env: &mut Environment) -> EvalResult<Value> {
+        (self.closure)(args, env)
+    }
+}
+
+impl Display for LoxExternFunction {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "<extern fun {}>", self.name)
+    }
+}
+
+impl Debug for LoxExternFunction {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("LoxExternFunction")
+            .field("name", &self.name)
+            .field("closure", &"<closure>")
+            .finish()
+    }
+}
+
+impl PartialEq for LoxExternFunction {
+    fn eq(&self, other: &Self) -> bool {
+        self.name == other.name
+    }
+}

interpreter/src/interpret.rs

@@ -0,0 +1,250 @@
+use std::rc::Rc;
+
+use rlox2_frontend::parser::{BinaryOp, Expr, Literal, LogicalOp, Stmt, UnaryOp};
+
+use crate::error::RuntimeError;
+use crate::LoxClass;
+
+use super::environment::Environment;
+use super::{LoxFunction, Runtime, Value};
+
+pub type EvalResult<T> = Result<T, RuntimeError>;
+
+/*====================================================================================================================*/
+
+pub fn execute(statement: Stmt, runtime: &mut Runtime) -> Result<(), RuntimeError> {
+    let mut env = Environment::new(runtime);
+
+    statement.eval(&mut env)?;
+
+    Ok(())
+}
+
+/*====================================================================================================================*/
+
+trait Eval {
+    fn eval(&self, env: &mut Environment) -> EvalResult<Value>;
+}
+
+impl Eval for Literal {
+    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)),
+            Literal::Bool(b) => Ok(Value::Bool(*b)),
+            Literal::Nil => Ok(Value::Nil),
+        }
+    }
+}
+
+impl Eval for Expr {
+    fn eval(&self, env: &mut Environment) -> EvalResult<Value> {
+        match self {
+            Expr::Literal { literal } => literal.eval(env),
+            Expr::Unary { op, expr } => {
+                let arg = expr.eval(env)?;
+
+                match (*op, arg) {
+                    (UnaryOp::Negate, Value::Number(num)) => Ok(Value::Number(-num)),
+                    (UnaryOp::Not, Value::Bool(b)) => Ok(Value::Bool(!b)),
+                    (UnaryOp::Not, primitive) => Ok(Value::Bool(!primitive.is_truthy())),
+                    (op, arg) => Err(RuntimeError::UnaryOpInvalidArgument { op, arg }),
+                }
+            }
+            Expr::Binary { left, op, right } => {
+                use Value::{Bool, Number, String};
+
+                let left = left.eval(env)?;
+                let right = right.eval(env)?;
+
+                match (left, *op, right) {
+                    (Number(left), BinaryOp::Add, Number(right)) => Ok(Number(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)) => {
+                        let mut s = std::string::String::with_capacity(left.capacity() + right.capacity());
+                        s += &left;
+                        s += &right;
+                        Ok(String(Rc::new(s)))
+                    }
+
+                    (left, BinaryOp::Equal, right) => Ok(Bool(left == right)),
+                    (left, BinaryOp::NotEqual, right) => Ok(Bool(left != right)),
+
+                    (Number(left), BinaryOp::Less, Number(right)) => Ok(Bool(left < right)),
+                    (Number(left), BinaryOp::LessEqual, Number(right)) => Ok(Bool(left <= right)),
+                    (Number(left), BinaryOp::Greater, Number(right)) => Ok(Bool(left > right)),
+                    (Number(left), BinaryOp::GreaterEqual, Number(right)) => Ok(Bool(left >= 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)),
+                    (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 => {
+                        if left.is_truthy() {
+                            return Ok(left);
+                        }
+                    }
+                    LogicalOp::And => {
+                        if !left.is_truthy() {
+                            return Ok(left);
+                        }
+                    }
+                }
+                let right = right.eval(env)?;
+                Ok(right)
+            }
+            Expr::Grouping { expr } => expr.eval(env),
+            Expr::Variable { name } => panic!("Unresolved variable {name}"),
+            Expr::LocalVariable { name, level } => env.get_local(name, *level),
+            Expr::GlobalVariable { name } => env.get_global(name),
+            Expr::Assignment { target, value } => {
+                let value = value.eval(env)?;
+
+                match target.as_ref() {
+                    Expr::LocalVariable { name, level } => env.assign(name, value.clone(), *level)?,
+                    Expr::GlobalVariable { name } => env.assign_global(name, value.clone())?,
+                    _ => panic!("Invalid assigment target {target}"),
+                }
+                Ok(value)
+            }
+            Expr::Call { callee, args } => {
+                let callee = callee.eval(env)?;
+                let args = args
+                    .iter()
+                    .map(|arg| arg.eval(env))
+                    .collect::<EvalResult<Vec<Value>>>()?;
+
+                match callee {
+                    Value::Function(fun) => fun.call(args, env),
+                    Value::ExternFunction(ext_fun) => ext_fun.call(args, env),
+                    _ => Err(RuntimeError::NotCallable { callee }),
+                }
+            }
+            Expr::Function {
+                name,
+                param_names,
+                closure_vars,
+                body,
+            } => Ok(Value::function(LoxFunction::new(
+                name,
+                env.collect_closure(closure_vars),
+                param_names.clone(),
+                body.as_ref().clone(),
+            ))),
+        }
+    }
+}
+
+impl Eval for Stmt {
+    fn eval(&self, env: &mut Environment) -> EvalResult<Value> {
+        match self {
+            Stmt::Print { expr } => {
+                match expr.eval(env)? {
+                    // special case: when printing a string, drop the surrounding ""
+                    Value::String(s) => println!("{s}"),
+                    val => println!("{val}"),
+                }
+            }
+            Stmt::IfStmt {
+                condition,
+                then_branch,
+                else_branch,
+            } => {
+                let condition = condition.eval(env)?;
+                if condition.is_truthy() {
+                    then_branch.eval(env)?;
+                } else if let Some(else_branch) = else_branch {
+                    else_branch.eval(env)?;
+                }
+            }
+            Stmt::While { condition, body } => {
+                while condition.eval(env)?.is_truthy() {
+                    match body.eval(env) {
+                        Ok(_) => {}
+                        Err(RuntimeError::Break) => break,
+                        Err(err) => return Err(err),
+                    }
+                }
+            }
+            Stmt::VarDecl { name, initializer } => {
+                let initializer = initializer.eval(env)?;
+                env.define(name, initializer);
+            }
+            Stmt::Block { statements } => {
+                env.enter_scope();
+                for statement in statements {
+                    if let Err(err) = statement.eval(env) {
+                        env.exit_scope();
+                        return Err(err);
+                    }
+                }
+                env.exit_scope();
+            }
+            Stmt::Class { name, methods: _ } => {
+                env.define(name, Value::Nil);
+
+                let class = Value::class(LoxClass::new(name));
+
+                env.assign(name, class, 0)?;
+            }
+            Stmt::ExprStmt { expr } => {
+                // expr.eval(env)?;
+                // Ok(Value::Nil)
+                expr.eval(env)?;
+            }
+            Stmt::Break => return Err(RuntimeError::Break),
+            Stmt::Return { expr } => {
+                let value = expr.eval(env)?;
+                return Err(RuntimeError::Return { value });
+            }
+        }
+
+        Ok(Value::Nil)
+    }
+}
+
+/*====================================================================================================================*/
+
+impl LoxFunction {
+    pub fn call(&self, args: Vec<Value>, env: &mut Environment) -> EvalResult<Value> {
+        if args.len() != self.arity() {
+            return Err(RuntimeError::WrongArity {
+                name: self.name().to_owned(),
+                arity: self.arity(),
+                given: args.len(),
+            });
+        }
+
+        env.push_scope(self.closure().clone());
+
+        for (name, value) in std::iter::zip(self.param_names(), args) {
+            env.define(name, value);
+        }
+
+        let ret_val = match self.body().eval(env) {
+            Ok(_) => Ok(Value::Nil),
+            Err(RuntimeError::Return { value }) => Ok(value),
+            Err(err) => Err(err),
+        };
+
+        env.exit_scope();
+
+        ret_val
+    }
+}

interpreter/src/lib.rs

@@ -0,0 +1,18 @@
+mod class;
+mod environment;
+mod error;
+mod function;
+mod interpret;
+mod lox_std;
+mod resolver;
+mod run;
+mod runtime;
+mod value;
+
+pub use class::LoxClass;
+pub use error::{LoxError, RuntimeError};
+pub use function::LoxFunction;
+pub use resolver::{resolve, ResolverError};
+pub use run::{run_file, run_repl};
+pub use runtime::Runtime;
+pub use value::Value;

interpreter/src/lox_std.rs

@@ -0,0 +1,113 @@
+use crate::error::RuntimeError;
+
+use super::function::{ExternFunClosure, LoxExternFunction};
+use super::{Runtime, Value};
+
+pub fn init_std(env: &mut Runtime) {
+    clock().register(env);
+    exit().register(env);
+    input().register(env);
+    print_env().register(env);
+    print_globals().register(env);
+}
+
+fn input() -> LoxExternFunction {
+    let closure: ExternFunClosure = |args, _env| match *args {
+        [] => {
+            let mut buf = String::new();
+            std::io::stdin()
+                .read_line(&mut buf)
+                .map_err(|err| RuntimeError::ExtFunCallFailed {
+                    name: "input".to_owned(),
+                    msg: format!("input() failed to read from stdin: {err}"),
+                })?;
+
+            assert_eq!(buf.pop(), Some('\n'));
+
+            Ok(Value::string(buf))
+        }
+        _ => Err(RuntimeError::ExtFunCallFailed {
+            name: "input".to_owned(),
+            msg: "input() takes no arguments".to_owned(),
+        }),
+    };
+
+    LoxExternFunction::new("input", closure)
+}
+
+fn clock() -> LoxExternFunction {
+    let closure: ExternFunClosure = |args, _env| match *args {
+        [] => {
+            let time = std::time::SystemTime::now()
+                .duration_since(std::time::UNIX_EPOCH)
+                .unwrap()
+                .as_secs_f64();
+
+            Ok(Value::Number(time))
+        }
+        _ => Err(RuntimeError::ExtFunCallFailed {
+            name: "clock".to_owned(),
+            msg: "clock() takes no arguments".to_owned(),
+        }),
+    };
+
+    LoxExternFunction::new("clock", closure)
+}
+
+fn print_globals() -> LoxExternFunction {
+    let closure: ExternFunClosure = |args, env| match *args {
+        [] => {
+            let mut globals: Vec<(&String, &Value)> = env.globals().iter().collect();
+
+            globals.sort_by_key(|&(name, _value)| name);
+
+            for (name, value) in globals {
+                println!("{name}: {value}");
+            }
+
+            Ok(Value::Nil)
+        }
+        _ => Err(RuntimeError::ExtFunCallFailed {
+            name: "print_globals".to_owned(),
+            msg: "print_globals() takes no arguments".to_owned(),
+        }),
+    };
+
+    LoxExternFunction::new("print_globals", closure)
+}
+
+fn print_env() -> LoxExternFunction {
+    let closure: ExternFunClosure = |args, env| match *args {
+        [] => {
+            println!("{env}");
+            Ok(Value::Nil)
+        }
+        _ => Err(RuntimeError::ExtFunCallFailed {
+            name: "print_env".to_owned(),
+            msg: "print_env() takes no arguments".to_owned(),
+        }),
+    };
+
+    LoxExternFunction::new("print_env", closure)
+}
+
+fn exit() -> LoxExternFunction {
+    let closure: ExternFunClosure = |args, _env| {
+        match &*args {
+            [] => return Err(RuntimeError::Exit { exit_code: 0 }),
+            [Value::Number(exit_code)] => {
+                if exit_code.fract() == 0.0 {
+                    let exit_code = *exit_code as i32;
+                    return Err(RuntimeError::Exit { exit_code });
+                }
+            }
+            _ => {}
+        }
+        Err(RuntimeError::ExtFunCallFailed {
+            name: "exit".to_owned(),
+            msg: "Arguments to exit() must an integer or nothing for exit code 0".to_owned(),
+        })
+    };
+
+    LoxExternFunction::new("exit", closure)
+}

interpreter/src/resolver/error.rs

@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum ResolverError {
+    #[error("Can't read variable {name} in its own initializer.")]
+    VarInOwnInitializer { name: String },
+    #[error("Could not resolve variable {name}")]
+    UnresolvableVariable { name: String },
+    #[error("Return outside of function definition")]
+    ReturnOutsideFunction,
+}

interpreter/src/resolver/mod.rs

@@ -0,0 +1,5 @@
+mod error;
+mod resolve;
+
+pub use error::ResolverError;
+pub use resolve::resolve;

interpreter/src/resolver/resolve.rs

@@ -0,0 +1,276 @@
+use std::collections::HashMap;
+
+use rlox2_frontend::parser::{Expr, Stmt};
+
+use crate::Runtime;
+use crate::{LoxError, ResolverError};
+
+/*====================================================================================================================*/
+
+type ResolverScope = HashMap<String, ResolveStatus>;
+type ResolverFrame = Vec<ResolverScope>;
+
+/*====================================================================================================================*/
+
+#[derive(Debug, Clone, Copy)]
+enum ResolveStatus {
+    Declared,
+    Defined,
+}
+
+/*====================================================================================================================*/
+
+pub fn resolve(statement: &mut Stmt, runtime: &mut Runtime) -> Result<(), LoxError> {
+    let global_names = runtime.globals().keys().cloned();
+
+    let mut resolver = Resolver::new(global_names);
+
+    resolver.resolve_stmt(statement)?;
+
+    Ok(())
+}
+
+#[derive(Debug)]
+struct Resolver {
+    global_scope: ResolverScope,
+    // local_scopes: Vec<ResolverScope>,
+    frames: Vec<ResolverFrame>,
+
+    closure_vars: HashMap<String, usize>,
+}
+
+impl Resolver {
+    fn new(global_names: impl Iterator<Item = String>) -> Self {
+        let mut global_scope = ResolverScope::new();
+
+        for name in global_names {
+            global_scope.insert(name, ResolveStatus::Defined);
+        }
+
+        Resolver {
+            global_scope,
+            frames: vec![ResolverFrame::new()],
+            closure_vars: HashMap::new(),
+        }
+    }
+
+    fn local_scopes(&self) -> &ResolverFrame {
+        self.frames.last().unwrap()
+    }
+
+    fn local_scopes_mut(&mut self) -> &mut ResolverFrame {
+        self.frames.last_mut().unwrap()
+    }
+
+    fn enter_scope(&mut self) {
+        self.local_scopes_mut().push(ResolverScope::new());
+    }
+
+    fn exit_scope(&mut self) {
+        self.local_scopes_mut()
+            .pop()
+            .expect("Tried to pop from empty ResolverFrame");
+    }
+
+    fn push_frame(&mut self) {
+        self.frames.push(vec![ResolverScope::new()]);
+    }
+
+    fn pop_frame(&mut self) {
+        self.frames.pop().expect("Tried to pop non-existant ResolverFrame");
+    }
+
+    fn declare(&mut self, name: &str) {
+        let name = name.to_owned();
+        if let Some(local_scope) = self.local_scopes_mut().last_mut() {
+            local_scope.insert(name, ResolveStatus::Declared);
+        } else {
+            self.global_scope.insert(name, ResolveStatus::Declared);
+        }
+    }
+
+    fn define(&mut self, name: &str) {
+        let name = name.to_owned();
+        if let Some(local_scope) = self.local_scopes_mut().last_mut() {
+            local_scope.insert(name, ResolveStatus::Defined);
+        } else {
+            self.global_scope.insert(name, ResolveStatus::Declared);
+        }
+    }
+
+    fn check(&self, name: &str) -> Option<ResolveStatus> {
+        if let Some(local_scope) = self.local_scopes().last() {
+            local_scope.get(name).cloned()
+        } else {
+            self.global_scope.get(name).cloned()
+        }
+    }
+
+    fn resolve_var(&mut self, name: &str) -> Result<Expr, ResolverError> {
+        let name = name.to_owned();
+
+        let mut level = 0;
+
+        for scope in self.local_scopes().iter().rev() {
+            if scope.contains_key(&name) {
+                return Ok(Expr::LocalVariable { name, level });
+            }
+            // DEBUG
+            level += 1;
+        }
+
+        for frame in self.frames.iter().rev().skip(1) {
+            for scope in frame.iter().rev() {
+                if scope.contains_key(&name) {
+                    if !self.closure_vars.contains_key(&name) {
+                        // the level at which the closed-over variable will be collected from
+                        // from the perspective of the parameter/closure scope i.e. the outmost of the function
+                        self.closure_vars
+                            .insert(name.clone(), level - self.local_scopes().len());
+                    }
+                    return Ok(Expr::LocalVariable {
+                        name,
+                        // distance from actual variable refernce to parameter/closure scope
+                        level: self.local_scopes().len() - 1,
+                    });
+                }
+                level += 1;
+            }
+        }
+
+        if self.global_scope.contains_key(&name) {
+            return Ok(Expr::GlobalVariable { name });
+        }
+
+        Err(ResolverError::UnresolvableVariable { name })
+    }
+
+    fn resolve_stmt(&mut self, stmt: &mut Stmt) -> Result<(), ResolverError> {
+        match stmt {
+            Stmt::Print { expr } => self.resolve_expr(expr),
+            Stmt::IfStmt {
+                condition,
+                then_branch,
+                else_branch,
+            } => {
+                self.resolve_expr(condition)?;
+                self.resolve_stmt(then_branch)?;
+                if let Some(else_branch) = else_branch {
+                    self.resolve_stmt(else_branch)?;
+                }
+                Ok(())
+            }
+            Stmt::While { condition, body } => {
+                self.resolve_expr(condition)?;
+                self.resolve_stmt(body)?;
+                Ok(())
+            }
+            Stmt::VarDecl { name, initializer } => {
+                self.declare(name);
+                self.resolve_expr(initializer)?;
+                self.define(name);
+                Ok(())
+            }
+            Stmt::Block { statements } => {
+                self.enter_scope();
+                for statement in statements.iter_mut() {
+                    self.resolve_stmt(statement)?;
+                }
+                self.exit_scope();
+                Ok(())
+            }
+            Stmt::Class { name, methods: _ } => {
+                self.declare(name);
+                self.define(name);
+                Ok(())
+            }
+            Stmt::ExprStmt { expr } => self.resolve_expr(expr),
+            Stmt::Break => Ok(()),
+            Stmt::Return { expr } => self.resolve_expr(expr),
+        }
+    }
+
+    fn resolve_expr(&mut self, expr: &mut Expr) -> Result<(), ResolverError> {
+        match expr {
+            Expr::Literal { literal: _ } => Ok(()),
+            Expr::Unary { op: _, expr } => self.resolve_expr(expr),
+            Expr::Binary { left, op: _, right } => {
+                self.resolve_expr(left)?;
+                self.resolve_expr(right)?;
+                Ok(())
+            }
+            Expr::Logical { left, op: _, right } => {
+                self.resolve_expr(left)?;
+                self.resolve_expr(right)?;
+                Ok(())
+            }
+            Expr::Grouping { expr } => self.resolve_expr(expr),
+            Expr::Variable { name } => {
+                if let Some(ResolveStatus::Declared) = self.check(name) {
+                    let name = name.clone();
+                    return Err(ResolverError::VarInOwnInitializer { name });
+                }
+
+                *expr = self.resolve_var(name)?;
+
+                Ok(())
+            }
+            Expr::LocalVariable { name, level: _ } => {
+                panic!("Tried to resolve variable {name} twice")
+            }
+            Expr::GlobalVariable { name } => {
+                panic!("Tried to resolve variable {name} twice")
+            }
+
+            Expr::Assignment { target, value } => {
+                self.resolve_expr(value)?;
+
+                let target = target.as_mut();
+                if let Expr::Variable { name } = target {
+                    *target = self.resolve_var(name)?;
+                } else {
+                    panic!("Invalid assignment target {target}");
+                }
+
+                Ok(())
+            }
+            Expr::Call { callee, args } => {
+                self.resolve_expr(callee)?;
+                for arg in args.iter_mut() {
+                    self.resolve_expr(arg)?;
+                }
+                Ok(())
+            }
+            Expr::Function {
+                name,
+                param_names,
+                closure_vars,
+                body,
+            } => {
+                let old_closure_names = std::mem::take(&mut self.closure_vars);
+
+                self.push_frame();
+
+                self.declare(name);
+                self.define(name);
+
+                for param_name in param_names {
+                    self.declare(param_name);
+                    self.define(param_name);
+                }
+
+                self.resolve_stmt(body)?;
+
+                self.pop_frame();
+
+                let closure_names = std::mem::replace(&mut self.closure_vars, old_closure_names);
+
+                for closure_var in closure_names {
+                    closure_vars.push(closure_var);
+                }
+
+                Ok(())
+            }
+        }
+    }
+}

interpreter/src/run.rs

@@ -0,0 +1,116 @@
+use std::io::Write;
+
+use rlox2_frontend::lexer::{scan_tokens, Token};
+use rlox2_frontend::parser::parse_tokens;
+
+use crate::error::LoxError;
+use crate::interpret::execute;
+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();
+
+    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, runtime) {
+            Ok(()) => {}
+            Err(LoxError::Exit { exit_code }) => std::process::exit(exit_code),
+            Err(err) => eprintln!("{err}"),
+        }
+    }
+}
+
+fn run(code_string: &str, runtime: &mut Runtime) -> Result<(), LoxError> {
+    let tokens: Vec<Token> = scan_tokens(code_string)?;
+
+    /* let token_str = tokens
+        .iter()
+        .map(|token| token.to_string())
+        .join(" ");
+
+    println!("{token_str}"); */
+
+    let statements = parse_tokens(tokens)?;
+
+    /* for statement in statements.iter() {
+        println!("{statement}");
+    } */
+
+    /* for statement in statements.iter() {
+        println!("{statement}");
+    } */
+
+    for mut statement in statements {
+        resolve(&mut statement, runtime)?;
+        execute(statement, runtime)?;
+    }
+
+    Ok(())
+}

interpreter/src/runtime.rs

@@ -0,0 +1,101 @@
+use std::collections::HashMap;
+use std::fmt::Display;
+use std::io::{stdin, stdout, Read, Write};
+
+use crate::error::RuntimeError;
+
+use super::lox_std::init_std;
+use super::Value;
+
+pub struct Runtime {
+    globals: HashMap<String, Value>,
+
+    in_stream: Box<dyn std::io::BufRead>,
+    out_stream: Box<dyn std::io::Write>,
+}
+
+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(),
+            in_stream,
+            out_stream,
+        };
+
+        init_std(&mut runtime);
+
+        runtime
+    }
+
+    pub fn globals(&self) -> &HashMap<String, Value> {
+        &self.globals
+    }
+
+    pub fn get_global(&self, name: &str) -> Result<Value, RuntimeError> {
+        self.globals
+            .get(name)
+            .cloned()
+            .ok_or_else(|| RuntimeError::GlobalNotDefined { name: name.to_owned() })
+    }
+
+    pub fn define_global(&mut self, name: impl Into<String>, value: Value) {
+        let name = name.into();
+        self.globals.insert(name, value);
+    }
+
+    pub fn assign_global(&mut self, name: &str, value: Value) -> Result<(), RuntimeError> {
+        if let Some(old_value) = self.globals.get_mut(name) {
+            *old_value = value;
+            Ok(())
+        } else {
+            Err(RuntimeError::GlobalNotDefined { name: name.to_owned() })
+        }
+    }
+}
+
+impl Default for Runtime {
+    fn default() -> Self {
+        Runtime::new(Box::new(std::io::BufReader::new(stdin())), Box::new(stdout()))
+    }
+}
+
+impl std::fmt::Debug for Runtime {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Runtime").field("globals", &self.globals).finish()
+    }
+}
+
+impl Display for Runtime {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Globals:")?;
+
+        for (name, value) in self.globals.iter() {
+            write!(f, "\n\t{name} = {value}")?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Drop for Runtime {
+    fn drop(&mut self) {
+        self.out_stream.flush().unwrap();
+    }
+}
+
+impl Read for Runtime {
+    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
+        self.in_stream.read(buf)
+    }
+}
+
+impl Write for Runtime {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        self.out_stream.write(buf)
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        self.out_stream.flush()
+    }
+}

interpreter/src/value.rs

@@ -0,0 +1,115 @@
+use std::cell::UnsafeCell;
+use std::fmt::{Debug, Display};
+use std::rc::Rc;
+
+use crate::LoxClass;
+
+use super::function::LoxExternFunction;
+use super::LoxFunction;
+
+#[derive(Debug, Clone)]
+pub enum Value {
+    Class(Rc<LoxClass>),
+    Function(Rc<LoxFunction>),
+    ExternFunction(Rc<LoxExternFunction>),
+    String(Rc<String>),
+    Number(f64),
+    Bool(bool),
+    Nil,
+}
+
+impl Value {
+    pub fn class(class: LoxClass) -> Self {
+        let class = Rc::new(class);
+        Value::Class(class)
+    }
+
+    pub fn function(fun: LoxFunction) -> Self {
+        let fun = Rc::new(fun);
+        Value::Function(fun)
+    }
+
+    pub fn extern_function(fun: LoxExternFunction) -> Self {
+        let fun = Rc::new(fun);
+        Value::ExternFunction(fun)
+    }
+
+    pub fn string(s: impl Into<String>) -> Self {
+        let s = Rc::new(s.into());
+        Value::String(s)
+    }
+
+    pub fn is_truthy(&self) -> bool {
+        !matches!(self, Value::Bool(false) | Value::Nil)
+    }
+}
+
+impl Display for Value {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Value::Class(class) => write!(f, "{class}"),
+            Value::Function(fun) => write!(f, "{fun}"),
+            Value::ExternFunction(ext_fun) => write!(f, "{ext_fun}"),
+            Value::String(s) => write!(f, "\"{s}\""),
+            Value::Number(num) => write!(f, "{num}"),
+            Value::Bool(b) => write!(f, "{b}"),
+            Value::Nil => write!(f, "nil"),
+        }
+    }
+}
+
+impl PartialEq for Value {
+    fn eq(&self, other: &Value) -> bool {
+        match (self, other) {
+            (Value::Function(l0), Value::Function(r0)) => Rc::ptr_eq(l0, r0),
+            (Value::ExternFunction(l0), Value::ExternFunction(r0)) => Rc::ptr_eq(l0, r0),
+            (Value::String(l0), Value::String(r0)) => l0 == r0,
+            (Value::Number(l0), Value::Number(r0)) => l0 == r0,
+            (Value::Bool(l0), Value::Bool(r0)) => l0 == r0,
+            (Value::Nil, Value::Nil) => true,
+            _ => false,
+        }
+    }
+}
+
+/*====================================================================================================================*/
+
+#[derive(Clone)]
+pub struct HeapedValue {
+    inner: Rc<UnsafeCell<Value>>,
+}
+
+impl HeapedValue {
+    pub fn new(value: Value) -> Self {
+        let inner = Rc::new(UnsafeCell::new(value));
+        HeapedValue { inner }
+    }
+
+    pub fn get_clone(&self) -> Value {
+        unsafe {
+            let ptr = self.inner.get();
+            let value = &*ptr;
+            value.clone()
+        }
+    }
+
+    pub fn replace(&mut self, value: Value) {
+        let mut value = value;
+        unsafe {
+            let ptr_mut = self.inner.get();
+            std::ptr::swap(&mut value, ptr_mut);
+        }
+    }
+}
+
+impl Debug for HeapedValue {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("HeapValue").field("inner", &self.get_clone()).finish()
+    }
+}
+
+impl Display for HeapedValue {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.get_clone())
+    }
+}