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refactoring Scanner

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Alpha Chen 2 years ago
parent 1320a0988f
commit 5d49f5ceea
Signed by: alpha
SSH Key Fingerprint: SHA256:3fOT8fiYQG/aK9ntivV3Bqtg8AYQ7q4nV6ZgihOA20g
1 changed files with 80 additions and 96 deletions
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176
rust/src/scanner.rs
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@ -4,8 +4,8 @@ pub struct Scanner<'a> {
line: usize,
}
fn is_alpha(c: char) -> bool {
c.is_ascii_alphabetic() || c == '_'
fn is_alpha(c: &char) -> bool {
c.is_ascii_alphabetic() || *c == '_'
}
impl<'a> Scanner<'a> {
@ -17,44 +17,32 @@ impl<'a> Scanner<'a> {
}
}
fn advance(&mut self) -> char {
fn advance(&mut self) -> Option<char> {
self.current += 1;
self.source[self.current - 1] as char
self.source.get(self.current - 1).map(|&x| x as char)
}
fn is_match(&mut self, expected: char) -> bool {
if self.peek() != Some(expected) {
return false;
fn advance_if<F: Fn(&char) -> bool>(&mut self, f: F) -> bool {
if matches!(self.peek(), Some(c) if f(&c)) {
self.current += 1;
true
} else {
false
}
self.current += 1;
true
}
fn skip_whitespace(&mut self) {
loop {
match self.peek() {
Some(' ') | Some('\r') | Some('\t') => {
self.advance();
break;
}
Some('\n') => {
self.line += 1;
self.advance();
break;
}
Some('/') => {
if matches!(self.peek_next(), Some(c) if c == '/') {
while matches!(self.peek(), Some(c) if c != '\n') {
self.advance();
}
} else {
return;
}
}
_ => {
return;
}
while self.advance_if(|&c| c == ' ' || c == '\r' || c == '\t') {}
if self.peek() == Some('/') && self.peek_next() == Some('/') {
while self.advance_if(|&c| c != '\n') {}
}
if self.advance_if(|&c| c == '\n') {
self.line += 1;
} else {
return;
}
}
}
@ -68,42 +56,34 @@ impl<'a> Scanner<'a> {
}
fn string(&mut self) -> Token<'a> {
while matches!(self.peek(), Some(c) if c != '"') {
if self.peek() == Some('\n') {
self.line += 1;
loop {
match self.advance() {
Some('"') => break,
Some('\n') => {
self.line += 1;
}
Some(_) => {}
None => return Token::error(self, "Unterminated string."),
}
self.advance();
}
if self.peek().is_none() {
// Maybe this should return an Err?
return Token::error(&self, "Unterminated string.");
}
self.advance();
Token::new(self, TokenKind::String)
}
fn number(&mut self) -> Token<'a> {
while matches!(self.peek(), Some(c) if c.is_ascii_digit()) {
self.advance();
}
while self.advance_if(char::is_ascii_digit) {}
if self.peek() == Some('.') && matches!(self.peek_next(), Some(c) if c.is_ascii_digit()) {
self.advance();
while matches!(self.peek(), Some(c) if c.is_ascii_digit()) {
self.advance();
}
while self.advance_if(char::is_ascii_digit) {}
}
Token::new(self, TokenKind::Number)
}
fn identifier(&mut self) -> Token<'a> {
while matches!(self.peek(), Some(c) if is_alpha(c) || c.is_ascii_digit()) {
self.advance();
}
while self.advance_if(|c| is_alpha(c) || c.is_ascii_digit()) {}
Token::new(self, self.identifier_type())
}
@ -143,55 +123,59 @@ impl<'a> Iterator for Scanner<'a> {
fn next(&mut self) -> Option<Self::Item> {
self.skip_whitespace();
if self.peek().is_none() {
return Some(Token::new(self, TokenKind::Eof));
}
Some(match self.advance() {
c if is_alpha(c) => self.identifier(),
c if c.is_ascii_digit() => self.number(),
'(' => Token::new(self, TokenKind::LeftParen),
')' => Token::new(self, TokenKind::RightParen),
'{' => Token::new(self, TokenKind::LeftBrace),
'}' => Token::new(self, TokenKind::RightBrace),
';' => Token::new(self, TokenKind::Semicolon),
',' => Token::new(self, TokenKind::Comma),
'.' => Token::new(self, TokenKind::Dot),
'-' => Token::new(self, TokenKind::Minus),
'+' => Token::new(self, TokenKind::Plus),
'/' => Token::new(self, TokenKind::Slash),
'*' => Token::new(self, TokenKind::Star),
'!' => {
if self.is_match('=') {
Token::new(self, TokenKind::BangEqual)
} else {
Token::new(self, TokenKind::Bang)
self.advance()
.map(|c| match c {
c if is_alpha(&c) => self.identifier(),
c if c.is_ascii_digit() => self.number(),
'(' => Token::new(self, TokenKind::LeftParen),
')' => Token::new(self, TokenKind::RightParen),
'{' => Token::new(self, TokenKind::LeftBrace),
'}' => Token::new(self, TokenKind::RightBrace),
';' => Token::new(self, TokenKind::Semicolon),
',' => Token::new(self, TokenKind::Comma),
'.' => Token::new(self, TokenKind::Dot),
'-' => Token::new(self, TokenKind::Minus),
'+' => Token::new(self, TokenKind::Plus),
'/' => Token::new(self, TokenKind::Slash),
'*' => Token::new(self, TokenKind::Star),
'!' => {
if self.advance_if(|&c| c == '=') {
Token::new(self, TokenKind::BangEqual)
} else {
Token::new(self, TokenKind::Bang)
}
}
}
'=' => {
if self.is_match('=') {
Token::new(self, TokenKind::EqualEqual)
} else {
Token::new(self, TokenKind::Equal)
'=' => {
if self.advance_if(|&c| c == '=') {
Token::new(self, TokenKind::EqualEqual)
} else {
Token::new(self, TokenKind::Equal)
}
}
}
'<' => {
if self.is_match('=') {
Token::new(self, TokenKind::LessEqual)
} else {
Token::new(self, TokenKind::Less)
'<' => {
if self.advance_if(|&c| c == '=') {
Token::new(self, TokenKind::LessEqual)
} else {
Token::new(self, TokenKind::Less)
}
}
}
'>' => {
if self.is_match('=') {
Token::new(self, TokenKind::GreaterEqual)
} else {
Token::new(self, TokenKind::Greater)
'>' => {
if self.advance_if(|&c| c == '=') {
Token::new(self, TokenKind::GreaterEqual)
} else {
Token::new(self, TokenKind::Greater)
}
}
}
'"' => self.string(),
_ => Token::error(self, "Unexpected character."),
})
'"' => self.string(),
_ => Token::error(self, "Unexpected character."),
})
.or({
Some(Token {
kind: TokenKind::Eof,
value: "",
line: self.line,
})
})
}
}

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