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|
use crate::tokenizer::{Token, TokenStream};
use crate::vm::{Value, Block, Op};
struct Compiler {
curr: usize,
tokens: TokenStream,
}
//TODO rustify
const PREC_NO: u64 = 0;
const PREC_COMP: u64 = 1;
const PREC_TERM: u64 = 2;
const PREC_FACTOR: u64 = 3;
impl Compiler {
pub fn new(tokens: TokenStream) -> Self {
Self {
curr: 0,
tokens,
}
}
fn error(&self, msg: &str) -> ! {
println!("ERROR: {} range {:?}", msg, self.tokens[self.curr].1);
panic!();
}
fn peek(&self) -> Token {
if self.tokens.len() <= self.curr {
crate::tokenizer::Token::EOF
} else {
self.tokens[self.curr].0.clone()
}
}
fn eat(&mut self) -> Token {
let t = self.peek();
self.curr += 1;
t
}
fn precedence(&self, token: Token) -> u64 {
match token {
Token::Minus => PREC_TERM,
Token::Plus => PREC_TERM,
Token::Star => PREC_FACTOR,
Token::Slash => PREC_FACTOR,
Token::EqualEqual => PREC_COMP,
_ => PREC_NO,
}
}
fn prefix(&mut self, token: Token, block: &mut Block) -> bool {
match token {
Token::LeftParen => self.grouping(block),
Token::Minus => self.unary(block),
Token::Float(_) => self.value(block),
Token::Int(_) => self.value(block),
_ => { return false; },
}
return true;
}
fn infix(&mut self, token: Token, block: &mut Block) -> bool {
match token {
Token::Minus => self.binary(block),
Token::Plus => self.binary(block),
Token::Slash => self.binary(block),
Token::Star => self.binary(block),
Token::EqualEqual => self.binary(block),
_ => { return false; },
}
return true;
}
fn value(&mut self, block: &mut Block) {
let value = match self.eat() {
Token::Float(f) => { Value::Float(f) },
Token::Int(f) => { Value::Int(f) }
_ => { self.error("Invalid value.") }
};
block.add(Op::Constant(value));
}
fn grouping(&mut self, block: &mut Block) {
if Token::LeftParen != self.eat() {
self.error("Expected left parenthesis around expression.");
}
self.expression(block);
if Token::RightParen != self.eat() {
self.error("Expected closing parenthesis after expression.");
}
}
fn unary(&mut self, block: &mut Block) {
if Token::Minus != self.eat() {
self.error("Expected minus at start of negation.");
}
self.value(block);
block.add(Op::Neg);
}
fn binary(&mut self, block: &mut Block) {
let op = self.eat();
self.parse_precedence(block, self.precedence(op.clone()) + 1);
let op = match op {
Token::Plus => Op::Add,
Token::Minus => Op::Sub,
Token::Star => Op::Mul,
Token::Slash => Op::Div,
Token::EqualEqual => Op::CompEq,
_ => { self.error("Illegal operator"); }
};
block.add(op);
}
fn expression(&mut self, block: &mut Block) {
self.parse_precedence(block, PREC_NO);
}
fn parse_precedence(&mut self, block: &mut Block, precedence: u64) {
println!("-- {:?}", self.peek());
if !self.prefix(self.peek(), block) {
self.error("Expected expression.");
}
while precedence <= self.precedence(self.peek()) {
if !self.infix(self.peek(), block) {
break;
}
}
}
pub fn compile(&mut self, name: &str) -> Block {
let mut block = Block::new(name);
loop {
if self.peek() == Token::EOF {
break;
}
self.expression(&mut block);
block.add(Op::Print);
if self.eat() != Token::Newline {
self.error("Invalid expression");
}
}
block.add(Op::Return);
block
}
}
pub fn compile(name: &str, tokens: TokenStream) -> Block {
Compiler::new(tokens).compile(name)
}
|
