From d0f83eb24ab904944b8e7976e98c9189ee1eb779 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Fri, 3 Feb 2017 11:15:50 -0800
Subject: [PATCH] add `push!` and `pop!`

---
 beautiful-racket-lib/br/list.rkt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/beautiful-racket-lib/br/list.rkt b/beautiful-racket-lib/br/list.rkt
index 2e97c8b..1ac1fd0 100644
--- a/beautiful-racket-lib/br/list.rkt
+++ b/beautiful-racket-lib/br/list.rkt
@@ -4,3 +4,11 @@
          
 (define-macro (values->list EXPR)
   #'(call-with-values (λ () EXPR) list))
+
+(define-macro (push! ID VAL)
+  #'(set! ID (cons VAL ID)))
+
+(define-macro (pop! ID)
+  #'(let ([x (car ID)])
+    (set! ID (cdr ID))
+    x))
\ No newline at end of file