From 33f03da3b01ca42bdd22ffb023ad7f3d7457a493 Mon Sep 17 00:00:00 2001
From: Nikodemus Siivola <nikodemus@random-state.net>
Date: Sun, 1 Jul 2007 15:21:10 +0300
Subject: [PATCH] ENSURE-CAR

---
 lists.lisp   | 6 ++++++
 package.lisp | 1 +
 2 files changed, 7 insertions(+)

diff --git a/lists.lisp b/lists.lisp
index 0a449ba..35565c9 100644
--- a/lists.lisp
+++ b/lists.lisp
@@ -126,6 +126,12 @@ recommended for performance intensive use. Main usefullness as the
 expected-type designator of a TYPE-ERROR."
   `(satisfies circular-list-p))
 
+(defun ensure-car (thing)
+  "If THING is a CONS, its CAR is returned. Otherwise THING is returned."
+  (if (consp thing)
+      (car thing)
+      thing))
+
 (defun ensure-cons (cons)
   "If CONS is a cons, it is returned. Otherwise returns a fresh cons with CONS
   in the car, and NIL in the cdr."
diff --git a/package.lisp b/package.lisp
index 76997ed..122c27a 100644
--- a/package.lisp
+++ b/package.lisp
@@ -40,6 +40,7 @@
    #:circular-list
    #:circular-list-p
    #:circular-tree-p
+   #:ensure-car
    #:ensure-cons
    #:ensure-list
    #:lastcar
-- 
2.11.4.GIT