Changing how parsing works again
Someone wrote a port of the LLVM kaleidoscope tutorial to rust, namely https://github.com/jauhien/iron-kaleidoscope I'm just gonna follow this along
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greg
parent
61c36c4def
commit
09d524c74a
@ -1,3 +1,4 @@
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/*
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use parser::AST;
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struct Evaluator {
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@ -100,3 +101,4 @@ mod tests {
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assert_eq!(output, "3");
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}
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}
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*/
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22
src/main.rs
22
src/main.rs
@ -11,13 +11,9 @@ use simplerepl::{REPL, ReplState};
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use tokenizer::tokenize;
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mod tokenizer;
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use parser::{ParseResult, parse};
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use parser::parse;
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mod parser;
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use evaluator::{evaluate};
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mod evaluator;
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fn main() {
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let args: Vec<String> = std::env::args().collect();
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println!("Schala v 0.02");
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@ -60,20 +56,14 @@ impl ReplState for InterpreterState {
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fn repl_handler(input: &str, state: &mut InterpreterState) -> String {
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if state.show_tokens {
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println!("Tokens: {:?}", tokenize(input))
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println!("Not implemented")
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}
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if state.show_parse {
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println!("Parse: {:?}", parse(tokenize(input)))
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println!("not implemented")
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}
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let parse_result = parse(tokenize(input));
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match parse_result {
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Ok(ast) => {
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format!("{}", evaluate(ast))
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},
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Err(err) => {
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format!("Parse error: {:?}", err)
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}
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}
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let tokens = tokenize(input);
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let ast = parse(&tokens);
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format!("Changing how parsing works again")
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}
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221
src/parser.rs
221
src/parser.rs
@ -1,222 +1,11 @@
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use std::iter::Peekable;
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use std::vec::IntoIter;
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use std::fmt;
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use tokenizer::Token;
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#[derive(Debug)]
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pub enum AST {
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BinOp(Box<AST>, Box<AST>, Box<AST>),
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Number(f64),
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Name(String),
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Block(Vec<AST>),
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Definition(String, Box<AST>),
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pub struct ParseResult {
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msg: i32
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}
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impl fmt::Display for AST {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self {
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&AST::Number(ref n) => write!(f, "{}", n),
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&AST::Name(ref s) => write!(f, "{}", s),
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astnode => write!(f, "UNEXPANDED AST NODE: {:?}", astnode)
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}
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}
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pub fn parse(tokens: &[Token]) -> ParseResult {
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ParseResult { msg: 0 }
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}
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#[derive(Debug)]
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pub struct ParseError {
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err: String
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}
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pub type ParseResult<T> = Result<T, ParseError>;
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/* grammar
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program : block EOF
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block : (statement sep)+
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sep : NEWLINE | SEMICOLON
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statement: expr | definition
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definition: 'let' NAME '=' expr
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expr : term ((PLUS|MIMUS) term)*
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term : factor ((MUL | DIV) factor)*
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factor : NUM | LPAREN expr RPAREN
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*/
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struct Parser {
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tokens: Peekable<IntoIter<Token>>
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}
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macro_rules! parse_error {
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($($text:tt)*) => {
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Err(ParseError { err: format!($($text)*) })
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}
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}
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impl Parser {
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fn next(&mut self) -> Option<Token> {
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self.tokens.next()
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}
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//TODO see if I can get rid of the need for this move
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fn lookahead(&mut self) -> Option<Token> {
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self.tokens.peek().map(|x| x.clone())
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}
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}
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impl Parser {
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fn expect(&mut self, expected: Token) -> ParseResult<()> {
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match self.next() {
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Some(ref next) if *next == expected => Ok(()),
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Some(next) => {
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return parse_error!("Expected {:?} but got {:?}", expected, next);
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},
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None => {
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return parse_error!("Expected {:?} but got end of input", expected);
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}
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}
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}
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fn expect_identifier(&mut self) -> ParseResult<String> {
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use tokenizer::Token::*;
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match self.next() {
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Some(Identifier(ref s)) => Ok(s.to_string()),
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Some(next) => {
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return parse_error!("Expected identifier but got {:?}", next);
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}
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None => {
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return parse_error!("Expected identifier but got end of input");
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}
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}
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}
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fn expect_num_literal(&mut self) -> ParseResult<f64> {
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use tokenizer::Token::*;
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match self.next() {
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Some(NumLiteral(f)) => Ok(f),
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Some(t) => {
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return parse_error!("Expected NumLiteral, but got {:?}", t);
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},
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None => {
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return parse_error!("Expected NumLiteral but got end of input");
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}
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}
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}
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fn parse(&mut self) -> ParseResult<AST> {
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let r = self.block();
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try!(self.expect(Token::EOF));
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r
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}
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fn block(&mut self) -> ParseResult<AST> {
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use tokenizer::Token::*;
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let mut block_nodes: Vec<AST> = Vec::new();
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loop {
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let s: AST = try!(self.statement());
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block_nodes.push(s);
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match self.lookahead() {
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Some(Semicolon) | Some(Newline) => {
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self.next();
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if let Some(EOF) = self.lookahead() {
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break
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}
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},
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_ => break
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}
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}
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Ok(AST::Block(block_nodes))
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}
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fn statement(&mut self) -> ParseResult<AST> {
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use tokenizer::Token::*;
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use tokenizer::Kw;
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let r = match self.lookahead() {
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Some(Keyword(Kw::Let)) => try!(self.definition()),
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_ => try!(self.expr())
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};
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Ok(r)
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}
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fn definition(&mut self) -> ParseResult<AST> {
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use tokenizer::Token::*;
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use tokenizer::Kw;
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try!(self.expect(Keyword(Kw::Let)));
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let name = try!(self.expect_identifier());
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match self.lookahead() {
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Some(Keyword(Kw::Assign)) => { self.next(); },
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_ => return parse_error!("Expected `=`"),
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}
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let expr = try!(self.expr());
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Ok(AST::Definition(name, Box::new(expr)))
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}
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fn expr(&mut self) -> ParseResult<AST> {
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use tokenizer::Token::*;
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let mut lhs = try!(self.term());
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loop {
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match self.lookahead() {
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Some(Identifier(ref s)) if s == "+" || s == "-" => {
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let op_token = self.next().unwrap();
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let op = AST::Name(match op_token { Identifier(s) => s, _ => panic!("lol") });
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let rhs = try!(self.term());
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lhs = AST::BinOp(
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Box::new(lhs),
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Box::new(op),
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Box::new(rhs));
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},
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_ => break
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}
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}
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Ok(lhs)
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}
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fn term(&mut self) -> ParseResult<AST> {
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use tokenizer::Token::*;
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let mut lhs = try!(self.factor());
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loop {
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match self.lookahead() {
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Some(Identifier(ref s)) if s == "*" || s == "/" => {
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let op_token = self.next().unwrap();
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let op = AST::Name(match op_token { Identifier(s) => s, _ => panic!("lol") });
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let rhs = try!(self.factor());
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lhs = AST::BinOp(
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Box::new(lhs),
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Box::new(op),
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Box::new(rhs));
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},
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_ => break
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}
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}
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Ok(lhs)
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}
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fn factor(&mut self) -> ParseResult<AST> {
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use tokenizer::Token::*;
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match self.lookahead() {
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Some(LParen) => {
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self.next();
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let expr = try!(self.expr());
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try!(self.expect(RParen));
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Ok(expr)
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},
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Some(NumLiteral(n)) => {
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self.next();
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Ok(AST::Number(n))
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},
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x => parse_error!("Expected LParen or NumLiteral, got {:?}", x )
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}
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}
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}
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pub fn parse(input: Vec<Token>) -> ParseResult<AST> {
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let iter = input.into_iter().peekable();
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let mut parser = Parser { tokens: iter };
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return parser.parse();
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}
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@ -28,92 +28,9 @@ pub enum Kw {
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pub fn tokenize(input: &str) -> Vec<Token> {
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let mut tokens = Vec::new();
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let mut iterator = input.chars().peekable();
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fn ends_identifier(c: char) -> bool {
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match c {
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c if char::is_whitespace(c) => true,
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',' => true,
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';' => true,
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'(' => true,
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')' => true,
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_ => false
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}
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}
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while let Some(c) = iterator.next() {
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if char::is_whitespace(c) && c != '\n' {
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continue;
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} else if c == '"' {
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let mut buffer = String::with_capacity(20);
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loop {
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match iterator.next() {
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Some(x) if x == '"' => break,
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Some(x) => buffer.push(x),
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None => return tokens,
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}
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}
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tokens.push(Token::StrLiteral(buffer));
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} else if c == '#' {
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while let Some(x) = iterator.next() {
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if x == '\n' {
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break;
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}
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}
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} else if c == ';' {
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tokens.push(Token::Semicolon);
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} else if c == '\n' {
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tokens.push(Token::Newline);
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} else if c == '(' {
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tokens.push(Token::LParen);
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} else if c == ')' {
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tokens.push(Token::RParen);
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} else if c == ',' {
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tokens.push(Token::Comma);
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} else if c == '.' {
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tokens.push(Token::Period);
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} else {
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let mut buffer = String::with_capacity(20);
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buffer.push(c);
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while let Some(x) = iterator.peek().cloned() {
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if ends_identifier(x) {
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break;
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}
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buffer.push(iterator.next().unwrap());
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}
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match buffer.parse::<f64>() {
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Ok(f) => tokens.push(Token::NumLiteral(f)),
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_ => tokens.push(handle_identifier(buffer))
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}
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}
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}
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tokens.push(Token::EOF);
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tokens
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}
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fn handle_identifier(identifier: String) -> Token {
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let keyword = match &identifier[..] {
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"let" => Kw::Let,
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"if" => Kw::If,
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"then" => Kw::Then,
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"else" => Kw::Else,
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"while" => Kw::While,
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"end" => Kw::End,
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"fn" => Kw::Fn,
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"null" => Kw::Null,
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"=" => Kw::Assign,
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_ => return Token::Identifier(identifier)
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};
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return Token::Keyword(keyword);
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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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