Two character tokens, comments, spaces and new lines.

golox/internal/runner/scanner.go

@@ -58,21 +58,86 @@ func (s *Scanner) scanToken() {
 		s.addToken(SEMI)
 	case '*':
 		s.addToken(STAR)
+	case '!':
+		tok := BANG
+		if s.match('=') {
+			tok = BANG_EQUAL
+		}
+		s.addToken(tok)
+	case '=':
+		tok := EQUAL
+		if s.match('=') {
+			tok = EQUAL_EQUAL
+		}
+		s.addToken(tok)
+	case '<':
+		tok := LT
+		if s.match('=') {
+			tok = LTE
+		}
+		s.addToken(tok)
+	case '>':
+		tok := GT
+		if s.match('=') {
+			tok = GTE
+		}
+		s.addToken(tok)
+	case '/':
+		if s.match('/') {
+			// Consume all characters in a line comment.
+			for s.peek() != '\n' && !s.isAtEnd() {
+				s.advance()
+			}
+		} else {
+			s.addToken(SLASH)
+		}
+	// Ignore whitespace.
+	case ' ':
+	case '\t':
+	case '\r':
+	// Handle new lines.
+	case '\n':
+		s.line += 1
 	default:
 		lerrors.EmitError(s.line, "Unexpected character.")
 	}
 }
 
+// advance consumes a single character from the source.
 func (s *Scanner) advance() byte {
 	idx := s.current
 	s.current += 1
 	return s.source[idx]
 }
 
+// match returns true if the given byte is equal to the next one in source,
+// it consumes the character if so.
+func (s *Scanner) match(c byte) bool {
+	if s.isAtEnd() {
+		return false
+	}
+	if s.source[s.current] != c {
+		return false
+	}
+
+	// Next character in the source matches.
+	s.current += 1
+	return true
+}
+
+func (s *Scanner) peek() byte {
+	if s.isAtEnd() {
+		return 0
+	}
+	return s.source[s.current]
+}
+
+// addToken produces a single token without a literal value.
 func (s *Scanner) addToken(typ TokenType) {
 	s.addTokenWithLiteral(typ, nil)
 }
 
+// addTokenWithLiteral produces a single token with the given literal value.
 func (s *Scanner) addTokenWithLiteral(typ TokenType, literal interface{}) {
 	lexme := s.source[s.start:s.current]
 	s.tokens = append(

golox/test.lox

@@ -1 +1,3 @@
-{,{.(;)-}}*
+// this is a comment
+((  )){} // grouping stuff
+!*+-/=<> <= == // operators