From 18dbfba4dc8948a9e8134705d1c8da74447ac4cc Mon Sep 17 00:00:00 2001
From: Ed Langley <elangley@cj.com>
Date: Sun, 18 Nov 2018 14:45:15 -0800
Subject: [PATCH] Add function for following a function call with a side-effect

---
 lens.lisp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lens.lisp b/lens.lisp
index ecff11b..9aa5d47 100644
--- a/lens.lisp
+++ b/lens.lisp
@@ -178,6 +178,11 @@
                        (apply f args))
                      r)))))
 
+(defun =>> (fun1 fun2)
+  (lambda (i)
+    (prog1 (funcall fun1 i)
+      (funcall fun2))))
+
 (defun-ct derive (diff-fun &key (key #'identity))
   (lambda (list)
     (cons (cons nil (car list))