From b81703ed333872ad05dc0626a736fc2f92263db3 Mon Sep 17 00:00:00 2001
From: Andrew Wilcox <andrew.wilcox@gmail.com>
Date: Thu, 16 Jun 2011 12:38:08 -0700
Subject: [PATCH] extension

---
 path.arc |  6 +++++-
 path.t   | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/path.arc b/path.arc
index 82ad913..f62da4f 100644
--- a/path.arc
+++ b/path.arc
@@ -1,4 +1,4 @@
-(use arc cwd values)
+(use arc cwd values re)
 
 (ail-code (racket-require (racket-prefix-in racket- scheme/path)))
 
@@ -13,6 +13,10 @@
   (aif (ar-fnil (racket-file-name-from-path path))
         (racket-path->string it)))
 
+(def extension (path)
+  (aand (filepart path)
+        (cadr (re-match "\\.([^\\.]+)$" it))))
+
 (def fullpath (path (o basedir cwd))
   (racket-path->string
    (racket-simplify-path
diff --git a/path.t b/path.t
index af3e862..77941c3 100644
--- a/path.t
+++ b/path.t
@@ -31,6 +31,27 @@ nil
 > (filepart "foo")
 "foo"
 
+> (extension "foo")
+nil
+
+> (extension "foo.")
+nil
+
+> (extension "foo.a")
+"a"
+
+> (extension "foo.a.")
+nil
+
+> (extension "foo.arc")
+"arc"
+
+> (extension "/a/b/c/foo.bar/")
+nil
+
+> (extension "/a/b/c/foo.bar")
+"bar"
+
 > (fullpath "/a/b/c/foo.bar")
 "/a/b/c/foo.bar"