640 lines
23 KiB
Rust
640 lines
23 KiB
Rust
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//! This is an entire parser and interpreter for a dynamically-typed Rust-like expression-oriented
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//! programming language. See `sample.nrs` for sample source code.
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//! Run it with the following command:
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//! cargo run --example nano_rust -- examples/sample.nrs
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use ariadne::{Color, Fmt, Label, Report, ReportKind, Source};
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use chumsky::{prelude::*, stream::Stream};
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use std::{collections::HashMap, env, fmt, fs};
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pub type Span = std::ops::Range<usize>;
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#[derive(Clone, Debug, PartialEq, Eq, Hash)]
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enum Token {
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Null,
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Bool(bool),
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Num(String),
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Str(String),
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Op(String),
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Ctrl(char),
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Ident(String),
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Fn,
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Let,
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Print,
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If,
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Else,
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}
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impl fmt::Display for Token {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self {
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Token::Null => write!(f, "null"),
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Token::Bool(x) => write!(f, "{}", x),
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Token::Num(n) => write!(f, "{}", n),
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Token::Str(s) => write!(f, "{}", s),
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Token::Op(s) => write!(f, "{}", s),
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Token::Ctrl(c) => write!(f, "{}", c),
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Token::Ident(s) => write!(f, "{}", s),
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Token::Fn => write!(f, "fn"),
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Token::Let => write!(f, "let"),
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Token::Print => write!(f, "print"),
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Token::If => write!(f, "if"),
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Token::Else => write!(f, "else"),
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}
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}
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}
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fn lexer() -> impl Parser<char, Vec<(Token, Span)>, Error = Simple<char>> {
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// A parser for numbers
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let num = text::int(10)
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.chain::<char, _, _>(just('.').chain(text::digits(10)).or_not().flatten())
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.collect::<String>()
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.map(Token::Num);
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// A parser for strings
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let str_ = just('"')
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.ignore_then(filter(|c| *c != '"').repeated())
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.then_ignore(just('"'))
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.collect::<String>()
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.map(Token::Str);
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// A parser for operators
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let op = one_of("+-*/!=")
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.repeated()
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.at_least(1)
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.collect::<String>()
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.map(Token::Op);
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// A parser for control characters (delimiters, semicolons, etc.)
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let ctrl = one_of("()[]{};,").map(|c| Token::Ctrl(c));
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// A parser for identifiers and keywords
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let ident = text::ident().map(|ident: String| match ident.as_str() {
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"fn" => Token::Fn,
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"let" => Token::Let,
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"print" => Token::Print,
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"if" => Token::If,
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"else" => Token::Else,
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"true" => Token::Bool(true),
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"false" => Token::Bool(false),
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"null" => Token::Null,
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_ => Token::Ident(ident),
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});
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// A single token can be one of the above
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let token = num
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.or(str_)
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.or(op)
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.or(ctrl)
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.or(ident)
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.recover_with(skip_then_retry_until([]));
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let comment = just("//").then(take_until(just('\n'))).padded();
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token
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.map_with_span(|tok, span| (tok, span))
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.padded_by(comment.repeated())
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.padded()
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.repeated()
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}
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#[derive(Clone, Debug, PartialEq)]
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enum Value {
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Null,
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Bool(bool),
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Num(f64),
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Str(String),
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List(Vec<Value>),
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Func(String),
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}
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impl Value {
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fn num(self, span: Span) -> Result<f64, Error> {
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if let Value::Num(x) = self {
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Ok(x)
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} else {
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Err(Error {
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span,
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msg: format!("'{}' is not a number", self),
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})
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}
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}
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}
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impl std::fmt::Display 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::Null => write!(f, "null"),
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Self::Bool(x) => write!(f, "{}", x),
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Self::Num(x) => write!(f, "{}", x),
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Self::Str(x) => write!(f, "{}", x),
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Self::List(xs) => write!(
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f,
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"[{}]",
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xs.iter()
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.map(|x| x.to_string())
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.collect::<Vec<_>>()
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.join(", ")
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),
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Self::Func(name) => write!(f, "<function: {}>", name),
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}
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}
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}
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#[derive(Clone, Debug)]
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enum BinaryOp {
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Add,
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Sub,
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Mul,
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Div,
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Eq,
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NotEq,
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}
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pub type Spanned<T> = (T, Span);
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// An expression node in the AST. Children are spanned so we can generate useful runtime errors.
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#[derive(Debug)]
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enum Expr {
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Error,
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Value(Value),
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List(Vec<Spanned<Self>>),
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Local(String),
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Let(String, Box<Spanned<Self>>, Box<Spanned<Self>>),
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Then(Box<Spanned<Self>>, Box<Spanned<Self>>),
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Binary(Box<Spanned<Self>>, BinaryOp, Box<Spanned<Self>>),
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Call(Box<Spanned<Self>>, Vec<Spanned<Self>>),
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If(Box<Spanned<Self>>, Box<Spanned<Self>>, Box<Spanned<Self>>),
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Print(Box<Spanned<Self>>),
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}
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// A function node in the AST.
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#[derive(Debug)]
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struct Func {
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args: Vec<String>,
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body: Spanned<Expr>,
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}
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fn expr_parser() -> impl Parser<Token, Spanned<Expr>, Error = Simple<Token>> + Clone {
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recursive(|expr| {
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let raw_expr = recursive(|raw_expr| {
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let val = select! {
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Token::Null => Expr::Value(Value::Null),
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Token::Bool(x) => Expr::Value(Value::Bool(x)),
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Token::Num(n) => Expr::Value(Value::Num(n.parse().unwrap())),
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Token::Str(s) => Expr::Value(Value::Str(s)),
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}
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.labelled("value");
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let ident = select! { Token::Ident(ident) => ident.clone() }.labelled("identifier");
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// A list of expressions
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let items = expr
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.clone()
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.separated_by(just(Token::Ctrl(',')))
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.allow_trailing();
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// A let expression
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let let_ = just(Token::Let)
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.ignore_then(ident)
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.then_ignore(just(Token::Op("=".to_string())))
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.then(raw_expr)
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.then_ignore(just(Token::Ctrl(';')))
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.then(expr.clone())
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.map(|((name, val), body)| Expr::Let(name, Box::new(val), Box::new(body)));
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let list = items
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.clone()
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.delimited_by(just(Token::Ctrl('[')), just(Token::Ctrl(']')))
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.map(Expr::List);
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// 'Atoms' are expressions that contain no ambiguity
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let atom = val
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.or(ident.map(Expr::Local))
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.or(let_)
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.or(list)
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// In Nano Rust, `print` is just a keyword, just like Python 2, for simplicity
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.or(just(Token::Print)
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.ignore_then(
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expr.clone()
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.delimited_by(just(Token::Ctrl('(')), just(Token::Ctrl(')'))),
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)
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.map(|expr| Expr::Print(Box::new(expr))))
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.map_with_span(|expr, span| (expr, span))
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// Atoms can also just be normal expressions, but surrounded with parentheses
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.or(expr
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.clone()
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.delimited_by(just(Token::Ctrl('(')), just(Token::Ctrl(')'))))
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// Attempt to recover anything that looks like a parenthesised expression but contains errors
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.recover_with(nested_delimiters(
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Token::Ctrl('('),
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Token::Ctrl(')'),
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[
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(Token::Ctrl('['), Token::Ctrl(']')),
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(Token::Ctrl('{'), Token::Ctrl('}')),
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],
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|span| (Expr::Error, span),
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))
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// Attempt to recover anything that looks like a list but contains errors
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.recover_with(nested_delimiters(
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Token::Ctrl('['),
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Token::Ctrl(']'),
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[
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(Token::Ctrl('('), Token::Ctrl(')')),
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(Token::Ctrl('{'), Token::Ctrl('}')),
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],
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|span| (Expr::Error, span),
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));
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// Function calls have very high precedence so we prioritise them
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let call = atom
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.then(
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items
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.delimited_by(just(Token::Ctrl('(')), just(Token::Ctrl(')')))
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.map_with_span(|args, span: Span| (args, span))
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.repeated(),
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)
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.foldl(|f, args| {
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let span = f.1.start..args.1.end;
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(Expr::Call(Box::new(f), args.0), span)
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});
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// Product ops (multiply and divide) have equal precedence
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let op = just(Token::Op("*".to_string()))
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.to(BinaryOp::Mul)
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.or(just(Token::Op("/".to_string())).to(BinaryOp::Div));
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let product = call
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.clone()
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.then(op.then(call).repeated())
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.foldl(|a, (op, b)| {
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let span = a.1.start..b.1.end;
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(Expr::Binary(Box::new(a), op, Box::new(b)), span)
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});
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// Sum ops (add and subtract) have equal precedence
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let op = just(Token::Op("+".to_string()))
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.to(BinaryOp::Add)
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.or(just(Token::Op("-".to_string())).to(BinaryOp::Sub));
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let sum = product
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.clone()
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.then(op.then(product).repeated())
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.foldl(|a, (op, b)| {
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let span = a.1.start..b.1.end;
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(Expr::Binary(Box::new(a), op, Box::new(b)), span)
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});
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// Comparison ops (equal, not-equal) have equal precedence
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let op = just(Token::Op("==".to_string()))
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.to(BinaryOp::Eq)
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.or(just(Token::Op("!=".to_string())).to(BinaryOp::NotEq));
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let compare = sum
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.clone()
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.then(op.then(sum).repeated())
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.foldl(|a, (op, b)| {
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let span = a.1.start..b.1.end;
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(Expr::Binary(Box::new(a), op, Box::new(b)), span)
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});
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compare
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});
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// Blocks are expressions but delimited with braces
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let block = expr
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.clone()
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.delimited_by(just(Token::Ctrl('{')), just(Token::Ctrl('}')))
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// Attempt to recover anything that looks like a block but contains errors
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.recover_with(nested_delimiters(
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Token::Ctrl('{'),
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Token::Ctrl('}'),
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[
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(Token::Ctrl('('), Token::Ctrl(')')),
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(Token::Ctrl('['), Token::Ctrl(']')),
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],
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|span| (Expr::Error, span),
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));
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let if_ = recursive(|if_| {
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just(Token::If)
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.ignore_then(expr.clone())
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.then(block.clone())
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.then(
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just(Token::Else)
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.ignore_then(block.clone().or(if_))
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.or_not(),
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)
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.map_with_span(|((cond, a), b), span: Span| {
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(
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Expr::If(
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Box::new(cond),
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Box::new(a),
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Box::new(match b {
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Some(b) => b,
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// If an `if` expression has no trailing `else` block, we magic up one that just produces null
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None => (Expr::Value(Value::Null), span.clone()),
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}),
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),
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span,
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)
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})
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});
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// Both blocks and `if` are 'block expressions' and can appear in the place of statements
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let block_expr = block.or(if_).labelled("block");
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let block_chain = block_expr
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.clone()
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.then(block_expr.clone().repeated())
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.foldl(|a, b| {
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let span = a.1.start..b.1.end;
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(Expr::Then(Box::new(a), Box::new(b)), span)
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});
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block_chain
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// Expressions, chained by semicolons, are statements
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.or(raw_expr.clone())
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.then(just(Token::Ctrl(';')).ignore_then(expr.or_not()).repeated())
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.foldl(|a, b| {
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// This allows creating a span that covers the entire Then expression.
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// b_end is the end of b if it exists, otherwise it is the end of a.
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let a_start = a.1.start;
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let b_end = b.as_ref().map(|b| b.1.end).unwrap_or(a.1.end);
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(
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Expr::Then(
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Box::new(a),
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Box::new(match b {
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Some(b) => b,
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// Since there is no b expression then its span is empty.
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None => (Expr::Value(Value::Null), b_end..b_end),
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}),
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),
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a_start..b_end,
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)
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})
|
||
|
|
})
|
||
|
|
}
|
||
|
|
|
||
|
|
fn funcs_parser() -> impl Parser<Token, HashMap<String, Func>, Error = Simple<Token>> + Clone {
|
||
|
|
let ident = filter_map(|span, tok| match tok {
|
||
|
|
Token::Ident(ident) => Ok(ident.clone()),
|
||
|
|
_ => Err(Simple::expected_input_found(span, Vec::new(), Some(tok))),
|
||
|
|
});
|
||
|
|
|
||
|
|
// Argument lists are just identifiers separated by commas, surrounded by parentheses
|
||
|
|
let args = ident
|
||
|
|
.clone()
|
||
|
|
.separated_by(just(Token::Ctrl(',')))
|
||
|
|
.allow_trailing()
|
||
|
|
.delimited_by(just(Token::Ctrl('(')), just(Token::Ctrl(')')))
|
||
|
|
.labelled("function args");
|
||
|
|
|
||
|
|
let func = just(Token::Fn)
|
||
|
|
.ignore_then(
|
||
|
|
ident
|
||
|
|
.map_with_span(|name, span| (name, span))
|
||
|
|
.labelled("function name"),
|
||
|
|
)
|
||
|
|
.then(args)
|
||
|
|
.then(
|
||
|
|
expr_parser()
|
||
|
|
.delimited_by(just(Token::Ctrl('{')), just(Token::Ctrl('}')))
|
||
|
|
// Attempt to recover anything that looks like a function body but contains errors
|
||
|
|
.recover_with(nested_delimiters(
|
||
|
|
Token::Ctrl('{'),
|
||
|
|
Token::Ctrl('}'),
|
||
|
|
[
|
||
|
|
(Token::Ctrl('('), Token::Ctrl(')')),
|
||
|
|
(Token::Ctrl('['), Token::Ctrl(']')),
|
||
|
|
],
|
||
|
|
|span| (Expr::Error, span),
|
||
|
|
)),
|
||
|
|
)
|
||
|
|
.map(|((name, args), body)| (name, Func { args, body }))
|
||
|
|
.labelled("function");
|
||
|
|
|
||
|
|
func.repeated()
|
||
|
|
.try_map(|fs, _| {
|
||
|
|
let mut funcs = HashMap::new();
|
||
|
|
for ((name, name_span), f) in fs {
|
||
|
|
if funcs.insert(name.clone(), f).is_some() {
|
||
|
|
return Err(Simple::custom(
|
||
|
|
name_span.clone(),
|
||
|
|
format!("Function '{}' already exists", name),
|
||
|
|
));
|
||
|
|
}
|
||
|
|
}
|
||
|
|
Ok(funcs)
|
||
|
|
})
|
||
|
|
.then_ignore(end())
|
||
|
|
}
|
||
|
|
|
||
|
|
struct Error {
|
||
|
|
span: Span,
|
||
|
|
msg: String,
|
||
|
|
}
|
||
|
|
|
||
|
|
fn eval_expr(
|
||
|
|
expr: &Spanned<Expr>,
|
||
|
|
funcs: &HashMap<String, Func>,
|
||
|
|
stack: &mut Vec<(String, Value)>,
|
||
|
|
) -> Result<Value, Error> {
|
||
|
|
Ok(match &expr.0 {
|
||
|
|
Expr::Error => unreachable!(), // Error expressions only get created by parser errors, so cannot exist in a valid AST
|
||
|
|
Expr::Value(val) => val.clone(),
|
||
|
|
Expr::List(items) => Value::List(
|
||
|
|
items
|
||
|
|
.iter()
|
||
|
|
.map(|item| eval_expr(item, funcs, stack))
|
||
|
|
.collect::<Result<_, _>>()?,
|
||
|
|
),
|
||
|
|
Expr::Local(name) => stack
|
||
|
|
.iter()
|
||
|
|
.rev()
|
||
|
|
.find(|(l, _)| l == name)
|
||
|
|
.map(|(_, v)| v.clone())
|
||
|
|
.or_else(|| Some(Value::Func(name.clone())).filter(|_| funcs.contains_key(name)))
|
||
|
|
.ok_or_else(|| Error {
|
||
|
|
span: expr.1.clone(),
|
||
|
|
msg: format!("No such variable '{}' in scope", name),
|
||
|
|
})?,
|
||
|
|
Expr::Let(local, val, body) => {
|
||
|
|
let val = eval_expr(val, funcs, stack)?;
|
||
|
|
stack.push((local.clone(), val));
|
||
|
|
let res = eval_expr(body, funcs, stack)?;
|
||
|
|
stack.pop();
|
||
|
|
res
|
||
|
|
}
|
||
|
|
Expr::Then(a, b) => {
|
||
|
|
eval_expr(a, funcs, stack)?;
|
||
|
|
eval_expr(b, funcs, stack)?
|
||
|
|
}
|
||
|
|
Expr::Binary(a, BinaryOp::Add, b) => Value::Num(
|
||
|
|
eval_expr(a, funcs, stack)?.num(a.1.clone())?
|
||
|
|
+ eval_expr(b, funcs, stack)?.num(b.1.clone())?,
|
||
|
|
),
|
||
|
|
Expr::Binary(a, BinaryOp::Sub, b) => Value::Num(
|
||
|
|
eval_expr(a, funcs, stack)?.num(a.1.clone())?
|
||
|
|
- eval_expr(b, funcs, stack)?.num(b.1.clone())?,
|
||
|
|
),
|
||
|
|
Expr::Binary(a, BinaryOp::Mul, b) => Value::Num(
|
||
|
|
eval_expr(a, funcs, stack)?.num(a.1.clone())?
|
||
|
|
* eval_expr(b, funcs, stack)?.num(b.1.clone())?,
|
||
|
|
),
|
||
|
|
Expr::Binary(a, BinaryOp::Div, b) => Value::Num(
|
||
|
|
eval_expr(a, funcs, stack)?.num(a.1.clone())?
|
||
|
|
/ eval_expr(b, funcs, stack)?.num(b.1.clone())?,
|
||
|
|
),
|
||
|
|
Expr::Binary(a, BinaryOp::Eq, b) => {
|
||
|
|
Value::Bool(eval_expr(a, funcs, stack)? == eval_expr(b, funcs, stack)?)
|
||
|
|
}
|
||
|
|
Expr::Binary(a, BinaryOp::NotEq, b) => {
|
||
|
|
Value::Bool(eval_expr(a, funcs, stack)? != eval_expr(b, funcs, stack)?)
|
||
|
|
}
|
||
|
|
Expr::Call(func, args) => {
|
||
|
|
let f = eval_expr(func, funcs, stack)?;
|
||
|
|
match f {
|
||
|
|
Value::Func(name) => {
|
||
|
|
let f = &funcs[&name];
|
||
|
|
let mut stack = if f.args.len() != args.len() {
|
||
|
|
return Err(Error {
|
||
|
|
span: expr.1.clone(),
|
||
|
|
msg: format!("'{}' called with wrong number of arguments (expected {}, found {})", name, f.args.len(), args.len()),
|
||
|
|
});
|
||
|
|
} else {
|
||
|
|
f.args
|
||
|
|
.iter()
|
||
|
|
.zip(args.iter())
|
||
|
|
.map(|(name, arg)| Ok((name.clone(), eval_expr(arg, funcs, stack)?)))
|
||
|
|
.collect::<Result<_, _>>()?
|
||
|
|
};
|
||
|
|
eval_expr(&f.body, funcs, &mut stack)?
|
||
|
|
}
|
||
|
|
f => {
|
||
|
|
return Err(Error {
|
||
|
|
span: func.1.clone(),
|
||
|
|
msg: format!("'{:?}' is not callable", f),
|
||
|
|
})
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
Expr::If(cond, a, b) => {
|
||
|
|
let c = eval_expr(cond, funcs, stack)?;
|
||
|
|
match c {
|
||
|
|
Value::Bool(true) => eval_expr(a, funcs, stack)?,
|
||
|
|
Value::Bool(false) => eval_expr(b, funcs, stack)?,
|
||
|
|
c => {
|
||
|
|
return Err(Error {
|
||
|
|
span: cond.1.clone(),
|
||
|
|
msg: format!("Conditions must be booleans, found '{:?}'", c),
|
||
|
|
})
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
Expr::Print(a) => {
|
||
|
|
let val = eval_expr(a, funcs, stack)?;
|
||
|
|
println!("{}", val);
|
||
|
|
val
|
||
|
|
}
|
||
|
|
})
|
||
|
|
}
|
||
|
|
|
||
|
|
fn main() {
|
||
|
|
let src = fs::read_to_string(env::args().nth(1).expect("Expected file argument"))
|
||
|
|
.expect("Failed to read file");
|
||
|
|
|
||
|
|
let (tokens, mut errs) = lexer().parse_recovery(src.as_str());
|
||
|
|
|
||
|
|
let parse_errs = if let Some(tokens) = tokens {
|
||
|
|
//dbg!(tokens);
|
||
|
|
let len = src.chars().count();
|
||
|
|
let (ast, parse_errs) =
|
||
|
|
funcs_parser().parse_recovery(Stream::from_iter(len..len + 1, tokens.into_iter()));
|
||
|
|
|
||
|
|
//dbg!(ast);
|
||
|
|
if let Some(funcs) = ast.filter(|_| errs.len() + parse_errs.len() == 0) {
|
||
|
|
if let Some(main) = funcs.get("main") {
|
||
|
|
assert_eq!(main.args.len(), 0);
|
||
|
|
match eval_expr(&main.body, &funcs, &mut Vec::new()) {
|
||
|
|
Ok(val) => println!("Return value: {}", val),
|
||
|
|
Err(e) => errs.push(Simple::custom(e.span, e.msg)),
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
panic!("No main function!");
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
parse_errs
|
||
|
|
} else {
|
||
|
|
Vec::new()
|
||
|
|
};
|
||
|
|
|
||
|
|
errs.into_iter()
|
||
|
|
.map(|e| e.map(|c| c.to_string()))
|
||
|
|
.chain(parse_errs.into_iter().map(|e| e.map(|tok| tok.to_string())))
|
||
|
|
.for_each(|e| {
|
||
|
|
let report = Report::build(ReportKind::Error, (), e.span().start);
|
||
|
|
|
||
|
|
let report = match e.reason() {
|
||
|
|
chumsky::error::SimpleReason::Unclosed { span, delimiter } => report
|
||
|
|
.with_message(format!(
|
||
|
|
"Unclosed delimiter {}",
|
||
|
|
delimiter.fg(Color::Yellow)
|
||
|
|
))
|
||
|
|
.with_label(
|
||
|
|
Label::new(span.clone())
|
||
|
|
.with_message(format!(
|
||
|
|
"Unclosed delimiter {}",
|
||
|
|
delimiter.fg(Color::Yellow)
|
||
|
|
))
|
||
|
|
.with_color(Color::Yellow),
|
||
|
|
)
|
||
|
|
.with_label(
|
||
|
|
Label::new(e.span())
|
||
|
|
.with_message(format!(
|
||
|
|
"Must be closed before this {}",
|
||
|
|
e.found()
|
||
|
|
.unwrap_or(&"end of file".to_string())
|
||
|
|
.fg(Color::Red)
|
||
|
|
))
|
||
|
|
.with_color(Color::Red),
|
||
|
|
),
|
||
|
|
chumsky::error::SimpleReason::Unexpected => report
|
||
|
|
.with_message(format!(
|
||
|
|
"{}, expected {}",
|
||
|
|
if e.found().is_some() {
|
||
|
|
"Unexpected token in input"
|
||
|
|
} else {
|
||
|
|
"Unexpected end of input"
|
||
|
|
},
|
||
|
|
if e.expected().len() == 0 {
|
||
|
|
"something else".to_string()
|
||
|
|
} else {
|
||
|
|
e.expected()
|
||
|
|
.map(|expected| match expected {
|
||
|
|
Some(expected) => expected.to_string(),
|
||
|
|
None => "end of input".to_string(),
|
||
|
|
})
|
||
|
|
.collect::<Vec<_>>()
|
||
|
|
.join(", ")
|
||
|
|
}
|
||
|
|
))
|
||
|
|
.with_label(
|
||
|
|
Label::new(e.span())
|
||
|
|
.with_message(format!(
|
||
|
|
"Unexpected token {}",
|
||
|
|
e.found()
|
||
|
|
.unwrap_or(&"end of file".to_string())
|
||
|
|
.fg(Color::Red)
|
||
|
|
))
|
||
|
|
.with_color(Color::Red),
|
||
|
|
),
|
||
|
|
chumsky::error::SimpleReason::Custom(msg) => report.with_message(msg).with_label(
|
||
|
|
Label::new(e.span())
|
||
|
|
.with_message(format!("{}", msg.fg(Color::Red)))
|
||
|
|
.with_color(Color::Red),
|
||
|
|
),
|
||
|
|
};
|
||
|
|
|
||
|
|
report.finish().print(Source::from(&src)).unwrap();
|
||
|
|
});
|
||
|
|
}
|