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refactor: Minify redundant advance, associate Token lifetime with parser #51

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Merged
thatmagicalcat merged 1 commit into from
Jul 21, 2026
Merged

refactor: Minify redundant advance, associate Token lifetime with parser #51

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98 changes: 25 additions & 73 deletions src/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ impl<'a> Parser<'a> {
self.tokens.get(self.pos).map(|(_, j)| j)
}

fn advance(&mut self) -> Token<'_> {
fn advance(&mut self) -> Token<'a> {
let t = self.tokens[self.pos].clone();
self.pos += 1;
t.0
Expand Down Expand Up @@ -307,42 +307,27 @@ impl<'a> Parser<'a> {
}

fn parse_atom(&mut self) -> Result<Expr, ParseError> {
match self.peek() {
Some(Token::Number(s)) => {
let next = self.advance().clone();
match next {
Token::Number(s) => {
let s = s.to_string();
self.advance();
Ok(Expr::Number(s))
}
Some(Token::Ident(s)) => {
Token::Ident(s) => {
let s = s.to_string();
self.advance();
Ok(Expr::Ident(s))
}
Some(Token::LBrace) => {
self.advance();
Token::LBrace => {
let inner = self.parse_expr()?;
self.expect(Token::RBrace)?;
Ok(inner)
}
Some(Token::LParen) => {
self.advance();
Ok(Expr::Ident("(".into()))
}
Some(Token::RParen) => {
self.advance();
Ok(Expr::Ident(")".into()))
}
Some(Token::LBracket) => {
self.advance();
Ok(Expr::Ident("[".into()))
}
Some(Token::RBracket) => {
self.advance();
Ok(Expr::Ident("]".into()))
}
Some(Token::Command(name)) => {
Token::LParen => Ok(Expr::Ident("(".into())),
Token::RParen => Ok(Expr::Ident(")".into())),
Token::LBracket => Ok(Expr::Ident("[".into())),
Token::RBracket => Ok(Expr::Ident("]".into())),
Token::Command(name) => {
let name = name.to_string();
self.advance();
if name == "begin" {
self.parse_begin()
} else if name == "left" {
Expand All @@ -353,13 +338,11 @@ impl<'a> Parser<'a> {
self.parse_command(&name)
}
}
Some(Token::Escape(s)) => {
Token::Escape(s) => {
let s = s.to_string();
self.advance();
Ok(Expr::Escape(s))
}
Some(Token::Pipe) => {
self.advance();
Token::Pipe => {
let inner = self.parse_expr()?;
self.expect(Token::Pipe)?;
Ok(Expr::Command {
Expand All @@ -368,8 +351,7 @@ impl<'a> Parser<'a> {
args: vec![inner],
})
}
Some(Token::Minus) => {
self.advance();
Token::Minus => {
// Unary minus if an operand follows (`-x`), otherwise a bare
// symbol (`\pm`-style groups, `x^{-}`).
if self.can_start_atom() {
Expand All @@ -378,51 +360,21 @@ impl<'a> Parser<'a> {
Ok(Expr::Ident("-".into()))
}
}
Some(Token::Bang) => {
self.advance();
Ok(Expr::Ident("!".into()))
}
Some(Token::Ampersand) => {
self.advance();
Ok(Expr::Ident("&".into()))
}
Some(Token::Plus) => {
self.advance();
Ok(Expr::Ident("+".into()))
}
Token::Bang => Ok(Expr::Ident("!".into())),
Token::Ampersand => Ok(Expr::Ident("&".into())),
Token::Plus => Ok(Expr::Ident("+".into())),
// Punctuation and relations that carry no special layout: render the
// literal symbol. Without these the tokens are dropped or collide
// with a closing-delimiter expectation (e.g. `(3,0)`, `x^{a/b}`).
Some(Token::Slash) => {
self.advance();
Ok(Expr::Ident("/".into()))
}
Some(Token::Comma) => {
self.advance();
Ok(Expr::Ident(",".into()))
}
Some(Token::Dot) => {
self.advance();
Ok(Expr::Ident(".".into()))
}
Some(Token::Colon) => {
self.advance();
Ok(Expr::Ident(":".into()))
}
Some(Token::Semicolon) => {
self.advance();
Ok(Expr::Ident(";".into()))
}
Some(Token::Less) => {
self.advance();
Ok(Expr::Ident("<".into()))
}
Some(Token::Greater) => {
self.advance();
Ok(Expr::Ident(">".into()))
}
Token::Slash => Ok(Expr::Ident("/".into())),
Token::Comma => Ok(Expr::Ident(",".into())),
Token::Dot => Ok(Expr::Ident(".".into())),
Token::Colon => Ok(Expr::Ident(":".into())),
Token::Semicolon => Ok(Expr::Ident(";".into())),
Token::Less => Ok(Expr::Ident("<".into())),
Token::Greater => Ok(Expr::Ident(">".into())),
other => Err(ParseError::UnexpectedToken {
position: self.pos,
position: self.pos - 1,
token: format!("{other:?}"),
}),
}
Expand Down