From c43ce00421e0b2688add6b89d94d2bb43313824b Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Sat, 29 Apr 2017 20:28:44 -0700
Subject: [PATCH] Change char-set->regexp to use string builder.

---
 src/runtime/regexp.scm | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/src/runtime/regexp.scm b/src/runtime/regexp.scm
index 468267752..3f3cb6d1e 100644
--- a/src/runtime/regexp.scm
+++ b/src/runtime/regexp.scm
@@ -195,22 +195,19 @@ USA.
 			   (loop (cdr ranges)
 				 (fix:+ n (if (pair? (car ranges)) 3 1)))
 			   n))))
-		(let ((s (make-legacy-string n)))
-		  (string-set! s 0 #\[)
-		  (let loop ((ranges ranges) (i 1))
+		(let ((builder (string-builder)))
+		  (builder #\[)
+		  (let loop ((ranges ranges))
 		    (if (pair? ranges)
-			(loop (cdr ranges)
-			      (let ((range (car ranges)))
-				(if (pair? range)
-				    (begin
-				      (string-set! s i (car range))
-				      (string-set! s (fix:+ i 1) #\-)
-				      (string-set! s (fix:+ i 2) (cdr range))
-				      (fix:+ i 3))
-				    (begin
-				      (string-set! s i range)
-				      (fix:+ i 1)))))
-			(string-set! s i #\])))
-		  s)))
+			(let ((range (car ranges)))
+			  (if (pair? range)
+			      (begin
+				(builder (car range))
+				(builder #\-)
+				(builder (cdr range)))
+			      (builder range)))
+			(loop (cdr ranges))))
+		  (builder #\])
+		  (builder))))
 	    (re-quote-string (string (car chars))))
 	"")))
\ No newline at end of file
-- 
2.25.1