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#![allow(dead_code, unused_variables, unused_mut)]
type ReToken = Box<RegexToken>;
#[derive(Debug, PartialEq, Clone)]
enum RegexToken {
Token(ReToken),
Symbol(char),
Number(usize),
Concat((ReToken, ReToken)),
Union((ReToken, ReToken)),
Star(ReToken),
Dot,
None,
}
macro_rules! Sym {
($c:expr) => {
RegexToken::Symbol($c)
};
}
macro_rules! Star {
($c:expr) => {
RegexToken::Star(Box::new($c))
};
}
macro_rules! Concat {
($a:expr, $b:expr) => {
RegexToken::Concat((Box::new($a), Box::new($b)))
};
}
macro_rules! Union {
($a:expr, $b:expr) => {
RegexToken::Union((Box::new($a), Box::new($b)))
};
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_concat() {
assert_eq!(
Regex::new(String::from("ab")),
Concat!(Sym!('a'), Sym!('b'))
)
}
#[test]
fn test_union() {
assert_eq!(
Regex::new(String::from("(a|b)")),
Concat!(Union!(Sym!('a'), Sym!('b')), RegexToken::None)
)
}
#[test]
fn test_none() {
assert_eq!(Regex::new(String::from("")), RegexToken::None)
}
#[test]
fn test_star() {
assert_eq!(
Regex::new(String::from("a*b")),
Concat!(Star!(Sym!('a')), Sym!('b'))
)
}
}
#[derive(Debug, PartialEq)]
struct Regex {}
impl Regex {
fn new(input: String) -> RegexToken {
Regex::parse(input)
}
fn parse(input: String) -> RegexToken {
if input.is_empty() {
return RegexToken::None;
}
let mut chars = input.chars().peekable();
let mut parsed_token = Self::parse_token(&mut RegexToken::None, &mut chars);
Self::parse_expression(&mut parsed_token, &mut chars)
}
fn parse_expression(
left: &mut RegexToken,
chars: &mut std::iter::Peekable<std::str::Chars>,
) -> RegexToken {
while let Some(&next) = chars.peek() {
match next {
'|' => {
chars.next(); // Consume '|'
let right = Self::parse_token(left, chars);
*left = RegexToken::Union((Box::new(left.clone()), Box::new(right)));
}
'*' => {
chars.next(); // Consume '|'
let right = Self::parse_token(left, chars);
*left = RegexToken::Star(Box::new(left.clone()));
}
_ => {
let right = Self::parse_token(left, chars);
*left = RegexToken::Concat((Box::new(left.clone()), Box::new(right)));
}
}
}
left.clone()
}
fn parse_token(
left: &mut RegexToken,
chars: &mut std::iter::Peekable<std::str::Chars>,
) -> RegexToken {
match chars.next() {
Some('(') => {
let token = Self::parse(chars.collect());
chars.next(); // Skip ')'
token
}
Some('.') => RegexToken::Dot,
Some(c) if c.is_ascii_alphanumeric() => Sym!(c),
Some('*') => {
let token = Self::parse_token(left, chars);
Star!(left.clone())
}
_ => RegexToken::None, // Handle other cases accordingly
}
}
}
fn main() {
let input = "a*b";
let token = Regex::new(String::from(input));
println!("{input}\n{:#?}", token)
}
|
