From 3f6b88bce231cfdc00fc7521fcb83d7114ad9142 Mon Sep 17 00:00:00 2001 From: Vincent Ambo Date: Fri, 27 Nov 2020 18:10:32 +0100 Subject: feat(tazjin/rlox): Implement multi-character scanning Change-Id: Ic5a246a7f5834477aeb97824fa30ba74a8422bc1 Reviewed-on: https://cl.tvl.fyi/c/depot/+/2161 Reviewed-by: tazjin Tested-by: BuildkiteCI --- users/tazjin/rlox/src/scanner.rs | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'users/tazjin/rlox/src') diff --git a/users/tazjin/rlox/src/scanner.rs b/users/tazjin/rlox/src/scanner.rs index 78a019592c..659f280de7 100644 --- a/users/tazjin/rlox/src/scanner.rs +++ b/users/tazjin/rlox/src/scanner.rs @@ -90,6 +90,7 @@ impl<'a> Scanner<'a> { fn scan_token(&mut self) { match self.advance() { + // simple single-character tokens '(' => self.add_token(TokenKind::LeftParen), ')' => self.add_token(TokenKind::RightParen), '{' => self.add_token(TokenKind::LeftBrace), @@ -101,6 +102,12 @@ impl<'a> Scanner<'a> { ';' => self.add_token(TokenKind::Semicolon), '*' => self.add_token(TokenKind::Star), + // possible multi-character tokens + '!' => self.add_if_next('=', TokenKind::BangEqual, TokenKind::Bang), + '=' => self.add_if_next('=', TokenKind::EqualEqual, TokenKind::Equal), + '<' => self.add_if_next('=', TokenKind::LessEqual, TokenKind::Less), + '>' => self.add_if_next('=', TokenKind::GreaterEqual, TokenKind::Greater), + unexpected => self.errors.push(Error { line: self.line, kind: ErrorKind::UnexpectedChar(unexpected), @@ -108,6 +115,15 @@ impl<'a> Scanner<'a> { }; } + fn add_if_next(&mut self, expected:char, then: TokenKind, or: TokenKind) { + if self.is_at_end() || self.source[self.current] != expected { + self.add_token(or); + } else { + self.current += 1; + self.add_token(then); + } + } + fn scan_tokens(mut self) -> Vec> { while !self.is_at_end() { self.start = self.current; -- cgit 1.4.1