--- old/CHANGELOG	2010-08-12 15:31:27.000000000 -0700
+++ new/CHANGELOG	2011-05-24 15:43:07.000000000 -0700
@@ -1,2 +1,4 @@
 2010-08-12: 2.0: Complete rewrite.
 
+2011-05-24: 2.1: Added extras/lexical.lisp.
+
--- old/extras/lexical.lisp	1969-12-31 16:00:00.000000000 -0800
+++ new/extras/lexical.lisp	2011-05-24 15:38:07.000000000 -0700
@@ -0,0 +1,43 @@
+; lexical.lisp   by Michael Thorpe   2011-05-24
+; Provides "lexical scope" for a block of functions.  Used as follows:
+;
+;	(lexical-let ((a 123))
+;		(define (getter) a)
+;		(define (setter new) (set a new) new))
+;
+;	(getter) ; returns 123
+;	(setter 432)
+;	(getter) ; returns 432
+
+(define (replace o from to)
+	(ifelse (pair? o)
+		(let ((a (replace (car o) from to))
+		      (d (replace (cdr o) from to)))
+			(ifelse (and (eq? a (car o)) (eq? d (cdr o)))
+				o
+				(cons a d)))
+		(ifelse (eq? o from)
+			to
+			(ifelse (quoted? o)
+				(let ((o2 (replace (unquote o) from to)))
+					(ifelse (eq? o2 (unquote o))
+						o
+						(quote o2)))
+				o))))
+
+(macro-define (lexical-let o)
+	(ifelse (pair? (cadr o))
+		(list
+			'#lexical-let
+			(quote (car (caadr o)))
+			(cons 'progn (cdr (caadr o)))
+			(quote (macro-expand (cons 'lexical-let (cons (cdadr o) (cddr o))))))
+		(cons 'progn (cddr o))))
+
+(macro-define (#lexical-let o)
+	(let ((new (unique-word))
+	      (old (unquote (cadr o))))
+		`(progn
+			(define ,new ,(macro-expand (caddr o)))
+			,(macro-expand (replace (unquote (cadddr o)) old new)))))
+