61 lines
1.8 KiB
Rust
61 lines
1.8 KiB
Rust
use std::io::{Bytes, Read};
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use std::iter::Peekable;
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pub type Number = i32;
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#[derive(PartialEq, Debug)]
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pub enum Token {
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Identifier(String),
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Number(Number),
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Operator(u8),
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}
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pub struct Lexer<R: Read> {
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reader: Peekable<Bytes<R>>,
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}
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impl<R: Read> Lexer<R> {
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pub fn new(reader: R) -> Lexer<R> {
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Lexer { reader: reader.bytes().peekable() }
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}
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}
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impl<R: Read> Iterator for Lexer<R> {
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type Item = Token;
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fn next(&mut self) -> Option<Token> {
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if let Some(Ok(ch)) = self.reader.next() {
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match ch {
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b'A' ..= b'Z' | b'a' ..= b'z' | b'\'' => {
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let mut identifier = String::new();
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identifier.push(ch as char);
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while let Some(Ok(b'A' ..= b'Z' | b'a' ..= b'z' | b'\'')) = self.reader.peek() {
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identifier.push(self.reader.next().unwrap().unwrap() as char);
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}
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Some(Token::Identifier(identifier))
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}
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b'0' ..= b'9' | b'-' => {
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let negative: bool;
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let mut number: Number = 0;
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if ch == b'-' {
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negative = true;
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} else {
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negative = false;
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number = (ch - b'0') as Number;
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}
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while let Some(Ok(b'0' ..= b'9')) = self.reader.peek() {
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number *= 10;
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number += (self.reader.next().unwrap().unwrap() - b'0') as Number;
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}
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if negative {
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number *= -1;
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}
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Some(Token::Number(number))
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}
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_ => Some(Token::Operator(ch))
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}
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} else {
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None
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}
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}
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} |