386 lines
10 KiB
Rust
386 lines
10 KiB
Rust
#![feature(let_else)]
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#![feature(array_windows)]
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#![feature(box_patterns)]
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mod grammar;
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#[cfg(test)]
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mod tests;
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// use debug2::dbg;
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use rustyline::validate::{
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MatchingBracketValidator, ValidationContext, ValidationResult, Validator,
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};
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use rustyline::Editor;
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use rustyline_derive::{Completer, Helper, Highlighter, Hinter};
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use std::collections::HashMap;
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use std::io;
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use std::rc::Rc;
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#[derive(Debug, debug2::Debug, PartialEq)]
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enum Tree {
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Leaf(Literal),
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Define(String, Box<Tree>),
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If(Box<[Tree; 3]>),
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Lambda(Lambda),
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Branch(Vec<Tree>),
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}
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#[derive(Debug, debug2::Debug, PartialEq, Clone)]
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struct Lambda(Rc<[String]>, Rc<[Tree]>);
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#[derive(Debug, debug2::Debug, PartialEq)]
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enum Literal {
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Sym(String),
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Num(f64),
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Bool(bool),
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}
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#[derive(Debug)]
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struct RTError(String);
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fn err<T>(s: String) -> Result<T, RTError> {
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Err(RTError(s))
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}
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type Func = fn(&[Value]) -> Result<Value, RTError>;
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#[derive(Clone)]
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enum Value {
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Num(f64),
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Func(Func),
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Lambda(Lambda),
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Bool(bool),
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NotAValue,
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}
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impl PartialEq for Value {
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fn eq(&self, other: &Self) -> bool {
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use Value::*;
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match (self, other) {
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(Num(l), Num(r)) => l == r,
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(Func(l), Func(r)) => *l as usize == *r as usize,
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(Bool(l), Bool(r)) => l == r,
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(Lambda(l), Lambda(r)) => Rc::ptr_eq(&l.0, &r.0) && Rc::ptr_eq(&l.1, &r.1),
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(Num(_), _) => false,
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(Func(_), _) => false,
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(Bool(_), _) => false,
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(Lambda(_), _) => false,
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(NotAValue, _) => panic!("Trap value"),
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}
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}
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}
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impl std::fmt::Debug for Value {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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match self {
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Self::Num(n) => n.fmt(f),
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Self::Func(_) => f.write_str("#<procedure>"),
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Self::Lambda(_) => f.write_str("#<procedure>"),
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Self::Bool(b) => f.write_str(if *b { "#t" } else { "#f" }),
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Self::NotAValue => Ok(()),
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}
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}
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}
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impl Value {
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fn as_num(&self) -> Result<f64, RTError> {
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if let Self::Num(n) = self {
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Ok(*n)
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} else {
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Err(RTError("Expected a number".to_owned()))
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}
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}
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fn as_func(&self) -> Result<Callable, RTError> {
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match self {
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Self::Func(f) => Ok(Callable::Func(*f)),
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Self::Lambda(l) => Ok(Callable::Lambda(l)),
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_ => Err(RTError(format!("Expected a function, got {:?}", self))),
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}
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}
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fn as_bool(&self) -> Result<bool, RTError> {
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if let Self::Bool(b) = self {
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Ok(*b)
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} else {
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Err(RTError("Expected a bool".to_owned()))
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}
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}
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}
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enum Callable<'a> {
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Func(Func),
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Lambda(&'a Lambda),
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}
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struct Env<'a> {
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vars: HashMap<String, Value>,
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enclosing: Option<&'a Env<'a>>,
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}
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impl<'a> Env<'a> {
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fn child(&'a self) -> Env<'a> {
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Env {
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vars: HashMap::new(),
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enclosing: Some(self),
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}
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}
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fn lookup(&self, s: &str) -> Option<Value> {
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if let Some(v) = self.vars.get(s) {
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Some(v.clone())
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} else if let Some(parent) = self.enclosing {
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parent.lookup(s)
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} else {
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None
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}
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}
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fn define(&mut self, name: String, val: Value) {
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self.vars.insert(name, val);
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}
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}
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fn main() {
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let args = std::env::args().collect::<Vec<_>>();
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match &args[..] {
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[_] => repl(),
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[_, file] => run_file(file).unwrap(),
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_ => panic!("To many args `{:?}`", args),
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}
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}
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fn run_file(file: &str) -> io::Result<()> {
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let src = std::fs::read_to_string(file)?;
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let tree = grammar::TreesParser::new().parse(&src).unwrap();
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let mut env = default_env();
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for i in tree {
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eval(&i, &mut env).unwrap();
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}
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Ok(())
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}
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fn repl() {
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let mut rl = Editor::new();
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rl.set_helper(Some(InputValidator {
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brackets: MatchingBracketValidator::new(),
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}));
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let mut env = default_env();
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while let Ok(line) = rl.readline("> ") {
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rl.add_history_entry(&line);
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let tree = grammar::TreeParser::new().parse(&line).unwrap();
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// dbg!(&tree);
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println!("< {:?}", eval(&tree, &mut env))
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}
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}
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fn eval(t: &Tree, env: &mut Env) -> Result<Value, RTError> {
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Ok(match t {
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Tree::Leaf(l) => match l {
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Literal::Sym(s) => match env.lookup(s) {
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Some(v) => v.clone(),
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None => return err(format!("Undefined variable `{}`", s)),
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},
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Literal::Num(v) => Value::Num(*v),
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Literal::Bool(b) => Value::Bool(*b),
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},
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Tree::Lambda(l) => Value::Lambda(l.clone()),
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Tree::Branch(args) => {
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let Some(fun) = args.get(0) else { return err("No argument given".to_owned()) };
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let fun = eval(fun, env)?;
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let fun = fun.as_func()?;
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let args = args
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.iter()
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.skip(1)
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.map(|a| eval(a, env))
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.collect::<Result<Vec<_>, _>>()?;
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// return fun(&args);
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match fun {
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Callable::Func(f) => f(&args)?,
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Callable::Lambda(l) => {
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if l.0.len() == args.len() {
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let mut env = env.child();
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for (x, y) in l.0.iter().zip(args) {
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env.define(x.clone(), y)
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}
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let [main @ .., tail] = &l.1[..] else { unreachable!("Body has 1+ element by parser") };
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for i in main {
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eval(i, &mut env)?;
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}
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eval(tail, &mut env)?
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} else {
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return err(format!("Need {} args, got {}", l.0.len(), args.len()));
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}
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}
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}
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}
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Tree::Define(name, to) => {
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let val = eval(to, env)?;
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env.define(name.to_owned(), val);
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Value::NotAValue
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}
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Tree::If(box [cond, tcase, fcase]) => {
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let b = eval(cond, env)?.as_bool()?;
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let body = if b { tcase } else { fcase };
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eval(body, env)?
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}
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})
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}
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fn default_env() -> Env<'static> {
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let mut vars = HashMap::new();
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for (name, fun) in [
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("*", prims::mul as Func),
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("+", prims::add as Func),
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("-", prims::sub as Func),
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("/", prims::div as Func),
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// TODO: Spec compiance
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("=", prims::equals as Func),
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("eq?", prims::equals as Func),
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("eqv?", prims::equals as Func),
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("equal?", prims::equals as Func),
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("display", prims::display as Func),
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("newline", prims::newline as Func),
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] {
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vars.insert(name.to_owned(), Value::Func(fun));
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}
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Env {
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vars,
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enclosing: None,
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}
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}
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mod prims {
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use crate::{err, RTError, Value};
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// TODO: DRY +-/*
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pub(crate) fn add(args: &[Value]) -> Result<Value, RTError> {
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args.iter()
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.map(Value::as_num)
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.try_fold(0.0, |a, b| Ok(a + b?))
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.map(Value::Num)
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}
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pub(crate) fn mul(args: &[Value]) -> Result<Value, RTError> {
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args.iter()
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.map(Value::as_num)
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.try_fold(1.0, |a, b| Ok(a * b?))
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.map(Value::Num)
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}
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pub(crate) fn div(args: &[Value]) -> Result<Value, RTError> {
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let init = args
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.get(0)
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.ok_or_else(|| RTError("`div` needs at least one argument".to_owned()))?
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.as_num()?;
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Ok(Value::Num(if args.len() == 1 {
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1.0 / init
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} else {
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let rest = mul(&args[1..])?.as_num().unwrap();
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init / rest
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}))
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}
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pub(crate) fn sub(args: &[Value]) -> Result<Value, RTError> {
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let init = args
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.get(0)
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.ok_or_else(|| RTError("`sub` needs at least one argument".to_owned()))?
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.as_num()?;
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Ok(Value::Num(if args.len() == 1 {
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-init
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} else {
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let rest = add(&args[1..])?.as_num().unwrap();
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init - rest
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}))
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}
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pub(crate) fn equals(args: &[Value]) -> Result<Value, RTError> {
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Ok(Value::Bool(args.array_windows().all(|[l, r]| l == r)))
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}
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pub(crate) fn display(args: &[Value]) -> Result<Value, RTError> {
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let [arg] = args else {return err("To many args to `display`".to_owned())};
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print!("{:?}", arg);
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Ok(Value::NotAValue)
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}
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pub(crate) fn newline(args: &[Value]) -> Result<Value, RTError> {
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if !args.is_empty() {
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return err("Newline takes no args".to_owned());
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}
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println!("");
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Ok(Value::NotAValue)
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}
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}
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// #[cfg(test)]
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// mod tests {
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// use super::*;
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// #[test]
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// fn simple_math_space() {
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// let t = grammar::TreeParser::new()
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// .parse("( + 1 2 ( / 2 3 4 5) )")
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// .unwrap();
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// assert_eq!(
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// t,
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// Tree::Add(vec![
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// Tree::Val(1.0),
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// Tree::Val(2.0),
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// Tree::Div(vec![
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// Tree::Val(2.0),
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// Tree::Val(3.0),
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// Tree::Val(4.0),
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// Tree::Val(5.0),
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// ])
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// ])
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// );
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// }
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// #[test]
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// fn simple_math_dence() {
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// let t = grammar::TreeParser::new()
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// .parse("(+ 1 2 (/ 2 3 4 5))")
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// .unwrap();
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// assert_eq!(
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// t,
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// Tree::Add(vec![
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// Tree::Val(1.0),
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// Tree::Val(2.0),
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// Tree::Div(vec![
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// Tree::Val(2.0),
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// Tree::Val(3.0),
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// Tree::Val(4.0),
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// Tree::Val(5.0),
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// ])
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// ])
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// );
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// }
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// }
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#[derive(Completer, Helper, Highlighter, Hinter)]
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struct InputValidator {
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brackets: MatchingBracketValidator,
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}
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impl Validator for InputValidator {
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fn validate(&self, ctx: &mut ValidationContext) -> rustyline::Result<ValidationResult> {
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self.brackets.validate(ctx)
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}
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}
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