From 104e3409cb1b0bfa357785343850f9351ae85d6e Mon Sep 17 00:00:00 2001
From: Botahamec <botahamec@outlook.com>
Date: Sun, 30 Jul 2023 13:12:12 -0400
Subject: Example lisp scanner

---
 examples/lisp.rs | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 examples/lisp.rs

diff --git a/examples/lisp.rs b/examples/lisp.rs
new file mode 100644
index 0000000..0fe6045
--- /dev/null
+++ b/examples/lisp.rs
@@ -0,0 +1,118 @@
+pub use snob::{csets, Scanner};
+
+pub const EXAMPLE_LIST_PROGRAM: &str = r"
+(defclass rewindable ()
+((rewind-store :reader rewind-store
+			   :initform (make-array 12 :fill-pointer 0 :adjustable t))
+ ;; Index is the number of rewinds we've done.
+ (rewind-index :accessor rewind-index
+			   :initform 0)))
+
+
+(defun rewind-count (rewindable)
+(fill-pointer (rewind-store rewindable)))
+
+
+(defun last-state (rewindable)
+(let ((size (rewind-count rewindable)))
+  (if (zerop size)
+	  (values nil nil)
+	  (values (aref (rewind-store rewindable) (1- size)) t))))
+
+
+(defun save-rewindable-state (rewindable object)
+(let ((index (rewind-index rewindable))
+	  (store (rewind-store rewindable)))
+  (unless (zerop index)
+	;; Reverse the tail of pool, since we've
+	;; gotten to the middle by rewinding.
+	(setf (subseq store index) (nreverse (subseq store index))))
+  (vector-push-extend object store)))
+
+
+(defmethod rewind-state ((rewindable rewindable))
+(invariant (not (zerop (rewind-count rewindable))))
+(setf (rewind-index rewindable)
+	  (mod (1+ (rewind-index rewindable)) (rewind-count rewindable)))
+(aref (rewind-store rewindable)
+	  (- (rewind-count rewindable) (rewind-index rewindable) 1)))
+";
+
+#[derive(Debug)]
+enum Token {
+	Dot,
+	Quote,
+	Function,
+	Integer(i64),
+	Symbol(String),
+	Comment(String),
+	LeftParenthesis,
+	RightParenthesis,
+}
+
+struct Tokenizer {
+	scanner: Scanner,
+}
+
+impl Tokenizer {
+	fn new(source: &str) -> Self {
+		Self {
+			scanner: Scanner::new(source),
+		}
+	}
+}
+
+impl Iterator for Tokenizer {
+	type Item = Token;
+
+	fn next(&mut self) -> Option<Self::Item> {
+		// skip over any whitespace
+		if let Some(position) = self.scanner.many(" \t\r\n") {
+			self.scanner.goto(position);
+		}
+
+		// terminate if done
+		if self.scanner.is_at_end() {
+			return None;
+		}
+
+		if let Some(position) = self.scanner.any('.') {
+			self.scanner.goto(position);
+			Some(Token::Dot)
+		} else if let Some(position) = self.scanner.any('\'') {
+			self.scanner.goto(position);
+			Some(Token::Quote)
+		} else if let Some(position) = self.scanner.any('(') {
+			self.scanner.goto(position);
+			Some(Token::LeftParenthesis)
+		} else if let Some(position) = self.scanner.any(')') {
+			self.scanner.goto(position);
+			Some(Token::RightParenthesis)
+		} else if let Some(position) = self.scanner.starts_with("#'") {
+			self.scanner.goto(position);
+			Some(Token::Function)
+		} else if let Some(position) = self.scanner.many(csets::AsciiDigits) {
+			let number = self.scanner.goto(position).unwrap();
+			let number = number.parse::<i64>().unwrap();
+			Some(Token::Integer(number))
+		} else if let Some(position) = self.scanner.any(';') {
+			self.scanner.goto(position);
+			let position = self.scanner.upto("\r\n").expect("Unterminated comment");
+			let comment = self.scanner.goto(position).unwrap();
+			Some(Token::Comment(comment))
+		} else {
+			let position = self
+				.scanner
+				.upto(" \t\r\n().\"'#")
+				.expect("unterminated symbol");
+			let symbol = self.scanner.goto(position).unwrap();
+			Some(Token::Symbol(symbol))
+		}
+	}
+}
+
+fn main() {
+	for token in Tokenizer::new(EXAMPLE_LIST_PROGRAM) {
+		println!("{token:?}");
+	}
+}
-- 
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