feat(tazjin/rlox): Add global variable support in interpreter
Change-Id: I4134cf78dc3934a517ad0c848ae1d3729abaf882 Reviewed-on: https://cl.tvl.fyi/c/depot/+/2297 Tested-by: BuildkiteCI Reviewed-by: tazjin <mail@tazj.in>
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4a86a06466
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2 changed files with 156 additions and 95 deletions
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@ -7,6 +7,8 @@ pub enum ErrorKind {
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ExpectedSemicolon,
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ExpectedSemicolon,
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ExpectedVariableName,
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ExpectedVariableName,
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TypeError(String),
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TypeError(String),
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UndefinedVariable(String),
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InternalError(String),
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}
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}
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#[derive(Debug)]
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#[derive(Debug)]
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@ -1,6 +1,7 @@
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use crate::errors::{report, Error, ErrorKind};
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use crate::errors::{report, Error, ErrorKind};
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use crate::parser::{self, Declaration, Expr, Literal, Program, Statement};
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use crate::parser::{self, Declaration, Expr, Literal, Program, Statement};
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use crate::scanner::{self, TokenKind};
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use crate::scanner::{self, TokenKind};
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use std::collections::HashMap;
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// Run some Lox code and print it to stdout
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// Run some Lox code and print it to stdout
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pub fn run(code: &str) {
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pub fn run(code: &str) {
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@ -9,8 +10,9 @@ pub fn run(code: &str) {
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match scanner::scan(&chars) {
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match scanner::scan(&chars) {
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Ok(tokens) => match parser::parse(tokens) {
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Ok(tokens) => match parser::parse(tokens) {
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Ok(program) => {
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Ok(program) => {
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let mut interpreter = Interpreter::default();
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println!("Program:\n{:?}", program);
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println!("Program:\n{:?}", program);
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if let Err(err) = run_program(&program) {
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if let Err(err) = interpreter.interpret(&program) {
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println!("Error in program: {:?}", err);
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println!("Error in program: {:?}", err);
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}
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}
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}
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}
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@ -28,6 +30,157 @@ fn report_errors(errors: Vec<Error>) {
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// Tree-walk interpreter
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// Tree-walk interpreter
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#[derive(Debug, Default)]
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struct Environment {
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values: HashMap<String, Literal>,
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}
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impl Environment {
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fn define(&mut self, name: &str, value: Literal) {
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self.values.insert(name.into(), value);
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}
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fn get(&self, name: &parser::Variable) -> Result<Literal, Error> {
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if let TokenKind::Identifier(ident) = &name.0.kind {
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return self
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.values
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.get(ident)
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.map(Clone::clone)
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.ok_or_else(|| Error {
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line: name.0.line,
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kind: ErrorKind::UndefinedVariable(ident.into()),
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});
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}
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Err(Error {
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line: name.0.line,
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kind: ErrorKind::InternalError("unexpected identifier kind".into()),
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})
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}
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}
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#[derive(Debug, Default)]
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struct Interpreter {
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globals: Environment,
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}
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impl Interpreter {
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fn interpret_stmt<'a>(&self, stmt: &Statement<'a>) -> Result<(), Error> {
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match stmt {
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Statement::Expr(expr) => {
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self.eval(expr)?;
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}
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Statement::Print(expr) => {
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let result = self.eval(expr)?;
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println!("{:?}", result)
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}
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}
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Ok(())
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}
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fn interpret_var<'a>(&mut self, var: &parser::Var<'a>) -> Result<(), Error> {
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if let TokenKind::Identifier(ident) = &var.name.kind {
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let init = var.initialiser.as_ref().ok_or_else(|| Error {
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line: var.name.line,
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kind: ErrorKind::InternalError("missing variable initialiser".into()),
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})?;
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self.globals.define(ident, self.eval(init)?);
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return Ok(());
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}
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Err(Error {
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line: var.name.line,
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kind: ErrorKind::InternalError("unexpected identifier kind".into()),
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})
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}
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pub fn interpret<'a>(&mut self, program: &Program<'a>) -> Result<(), Error> {
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for decl in program {
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match decl {
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Declaration::Stmt(stmt) => self.interpret_stmt(stmt)?,
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Declaration::Var(var) => self.interpret_var(var)?,
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}
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}
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Ok(())
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}
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fn eval<'a>(&self, expr: &Expr<'a>) -> Result<Literal, Error> {
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match expr {
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Expr::Literal(lit) => Ok(lit.clone()),
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Expr::Grouping(grouping) => self.eval(&*grouping.0),
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Expr::Unary(unary) => self.eval_unary(unary),
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Expr::Binary(binary) => self.eval_binary(binary),
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Expr::Variable(var) => self.globals.get(var),
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}
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}
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fn eval_unary<'a>(&self, expr: &parser::Unary<'a>) -> Result<Literal, Error> {
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let right = self.eval(&*expr.right)?;
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match (&expr.operator.kind, right) {
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(TokenKind::Minus, Literal::Number(num)) => Ok(Literal::Number(-num)),
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(TokenKind::Bang, right) => Ok(Literal::Boolean(!eval_truthy(&right))),
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(op, right) => Err(Error {
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line: expr.operator.line,
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kind: ErrorKind::TypeError(format!(
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"Operator '{:?}' can not be called with argument '{:?}'",
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op, right
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)),
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}),
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}
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}
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fn eval_binary<'a>(&self, expr: &parser::Binary<'a>) -> Result<Literal, Error> {
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let left = self.eval(&*expr.left)?;
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let right = self.eval(&*expr.right)?;
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let result = match (&expr.operator.kind, left, right) {
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// Numeric
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(TokenKind::Minus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l - r),
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(TokenKind::Slash, Literal::Number(l), Literal::Number(r)) => Literal::Number(l / r),
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(TokenKind::Star, Literal::Number(l), Literal::Number(r)) => Literal::Number(l * r),
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(TokenKind::Plus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l + r),
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// Strings
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(TokenKind::Plus, Literal::String(l), Literal::String(r)) => {
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Literal::String(format!("{}{}", l, r))
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}
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// Comparators (on numbers only?)
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(TokenKind::Greater, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l > r),
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(TokenKind::GreaterEqual, Literal::Number(l), Literal::Number(r)) => {
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Literal::Boolean(l >= r)
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}
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(TokenKind::Less, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l < r),
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(TokenKind::LessEqual, Literal::Number(l), Literal::Number(r)) => {
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Literal::Boolean(l <= r)
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}
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// Equality
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(TokenKind::Equal, l, r) => Literal::Boolean(l == r),
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(TokenKind::BangEqual, l, r) => Literal::Boolean(l != r),
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(op, left, right) => {
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return Err(Error {
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line: expr.operator.line,
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kind: ErrorKind::TypeError(format!(
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"Operator '{:?}' can not be called with arguments '({:?}, {:?})'",
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op, left, right
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)),
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})
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}
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};
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Ok(result)
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}
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}
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// Interpreter functions not dependent on interpreter-state.
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fn eval_truthy(lit: &Literal) -> bool {
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fn eval_truthy(lit: &Literal) -> bool {
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match lit {
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match lit {
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Literal::Nil => false,
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Literal::Nil => false,
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@ -35,97 +188,3 @@ fn eval_truthy(lit: &Literal) -> bool {
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_ => true,
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_ => true,
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}
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}
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}
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}
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fn eval_unary<'a>(expr: &parser::Unary<'a>) -> Result<Literal, Error> {
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let right = eval(&*expr.right)?;
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match (&expr.operator.kind, right) {
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(TokenKind::Minus, Literal::Number(num)) => Ok(Literal::Number(-num)),
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(TokenKind::Bang, right) => Ok(Literal::Boolean(!eval_truthy(&right))),
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(op, right) => Err(Error {
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line: expr.operator.line,
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kind: ErrorKind::TypeError(format!(
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"Operator '{:?}' can not be called with argument '{:?}'",
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op, right
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)),
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}),
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}
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}
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fn eval_binary<'a>(expr: &parser::Binary<'a>) -> Result<Literal, Error> {
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let left = eval(&*expr.left)?;
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let right = eval(&*expr.right)?;
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let result = match (&expr.operator.kind, left, right) {
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// Numeric
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(TokenKind::Minus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l - r),
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(TokenKind::Slash, Literal::Number(l), Literal::Number(r)) => Literal::Number(l / r),
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(TokenKind::Star, Literal::Number(l), Literal::Number(r)) => Literal::Number(l * r),
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(TokenKind::Plus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l + r),
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// Strings
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(TokenKind::Plus, Literal::String(l), Literal::String(r)) => {
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Literal::String(format!("{}{}", l, r))
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}
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// Comparators (on numbers only?)
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(TokenKind::Greater, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l > r),
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(TokenKind::GreaterEqual, Literal::Number(l), Literal::Number(r)) => {
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Literal::Boolean(l >= r)
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}
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(TokenKind::Less, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l < r),
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(TokenKind::LessEqual, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l <= r),
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// Equality
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(TokenKind::Equal, l, r) => Literal::Boolean(l == r),
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(TokenKind::BangEqual, l, r) => Literal::Boolean(l != r),
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(op, left, right) => {
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return Err(Error {
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line: expr.operator.line,
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kind: ErrorKind::TypeError(format!(
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"Operator '{:?}' can not be called with arguments '({:?}, {:?})'",
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op, left, right
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)),
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})
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}
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};
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Ok(result)
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}
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fn eval<'a>(expr: &Expr<'a>) -> Result<Literal, Error> {
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match expr {
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Expr::Literal(lit) => Ok(lit.clone()),
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Expr::Grouping(grouping) => eval(&*grouping.0),
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Expr::Unary(unary) => eval_unary(unary),
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Expr::Binary(binary) => eval_binary(binary),
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Expr::Variable(_) => unimplemented!(),
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}
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}
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fn run_stmt<'a>(stmt: &Statement<'a>) -> Result<(), Error> {
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match stmt {
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Statement::Expr(expr) => {
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eval(expr)?;
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}
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Statement::Print(expr) => {
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let result = eval(expr)?;
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println!("{:?}", result)
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}
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}
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Ok(())
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}
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fn run_program<'a>(program: &Program<'a>) -> Result<(), Error> {
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for decl in program {
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match decl {
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Declaration::Stmt(stmt) => run_stmt(stmt)?,
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Declaration::Var(_var) => unimplemented!(),
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}
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}
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Ok(())
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}
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