From d8989c2ae3d685b15c16491e30ae8d40580ed059 Mon Sep 17 00:00:00 2001
From: Eli Barzilay <eli@barzilay.org>
Date: Tue, 16 Jul 2013 01:30:51 -0400
Subject: Improve macro definition.

It's more robust to use `let' to have the macro result in its own new
scope.  (Unrelated to the hygiene point, of course.)
---
 racket.html.markdown | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/racket.html.markdown b/racket.html.markdown
index e528bc74..526d008c 100644
--- a/racket.html.markdown
+++ b/racket.html.markdown
@@ -423,8 +423,7 @@ vec ; => #(1 2 3 4)
 
 ;; Macros are hygienic, you cannot clobber existing variables!
 (define-syntax-rule (swap x y)
-  (begin
-    (define tmp x)
+  (let ([tmp x])
     (set! x y)
     (set! y tmp)))
 
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