148 lines
4.2 KiB
Rust
148 lines
4.2 KiB
Rust
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//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
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#[derive(PartialEq, Eq, Clone, Debug)]
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pub enum LadderTypeToken {
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Symbol( String ),
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Char( char ),
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Num( u64 ),
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Open,
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Close,
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Ladder,
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}
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#[derive(PartialEq, Eq, Clone, Debug)]
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pub enum LexError {
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/// found a non-digit character inside a numeric token
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InvalidDigit,
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/// quoted character token didnt close correctly with '
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InvalidChar,
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}
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//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
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#[derive(PartialEq, Eq, Clone, Debug)]
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enum LexerState {
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Any,
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Sym( String ),
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Num( u64 ),
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Char( Option<char> )
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}
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impl LexerState {
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fn into_token(self) -> Option<LadderTypeToken> {
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match self {
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LexerState::Any => None,
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LexerState::Sym(s) => Some(LadderTypeToken::Symbol(s)),
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LexerState::Num(n) => Some(LadderTypeToken::Num(n)),
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LexerState::Char(c) => Some(LadderTypeToken::Char(c?))
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}
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}
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}
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//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
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pub struct LadderTypeLexer<It>
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where It: std::iter::Iterator<Item = char>
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{
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chars: std::iter::Peekable<It>,
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}
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impl<It> LadderTypeLexer<It>
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where It: Iterator<Item = char>
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{
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pub fn new(chars: It) -> Self {
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LadderTypeLexer {
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chars: chars.peekable()
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}
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}
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}
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impl<It> Iterator for LadderTypeLexer<It>
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where It: Iterator<Item = char>
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{
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type Item = Result<LadderTypeToken, LexError>;
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fn next(&mut self) -> Option<Self::Item> {
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let mut state = LexerState::Any;
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while let Some(c) = self.chars.peek() {
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match &mut state {
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// determine token type
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LexerState::Any => {
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match c {
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'<' => { self.chars.next(); return Some(Ok(LadderTypeToken::Open)); },
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'>' => { self.chars.next(); return Some(Ok(LadderTypeToken::Close)); },
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'~' => { self.chars.next(); return Some(Ok(LadderTypeToken::Ladder)); },
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'\'' => { self.chars.next(); state = LexerState::Char(None); },
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' ' => { self.chars.next(); },
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c => {
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if c.is_alphabetic() {
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state = LexerState::Sym( String::new() );
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} else if c.is_digit(10) {
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state = LexerState::Num( 0 );
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}
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}
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}
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}
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LexerState::Char(val) => {
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// todo escape characters
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*val = self.chars.next();
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match self.chars.next() {
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Some('\'') => {
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if let Some(token) = state.clone().into_token() {
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return Some(Ok(token));
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}
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}
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_ => {
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return Some(Err(LexError::InvalidChar));
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}
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}
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}
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_ => {
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if c.is_whitespace() || *c == '>' || *c == '~' {
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// finish the current token
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if let Some(token) = state.clone().into_token() {
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return Some(Ok(token));
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}
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} else {
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// append to the current token
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let c = self.chars.next().unwrap();
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match &mut state {
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LexerState::Sym(s) => {
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s.push(c);
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}
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LexerState::Num(n) => {
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if let Some(d) = c.to_digit(10) {
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*n = (*n) * 10 + d as u64;
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} else {
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return Some(Err(LexError::InvalidDigit));
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}
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}
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_ => {}
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}
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}
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}
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}
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}
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if let Some(token) = state.into_token() {
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Some(Ok(token))
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} else {
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None
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}
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}
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}
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