add map-utils from Jason Wolfe, fixes issue 10

1 files changed, 37 insertions, 0 deletions

diff --git a/src/clojure/contrib/map_utils.clj b/src/clojure/contrib/map_utils.clj
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+++ b/src/clojure/contrib/map_utils.clj
@@ -0,0 +1,37 @@
+;;  Copyright (c) Jason Wolfe. All rights reserved.  The use and
+;;  distribution terms for this software are covered by the Eclipse Public
+;;  License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) which can
+;;  be found in the file epl-v10.html at the root of this distribution.  By
+;;  using this software in any fashion, you are agreeing to be bound by the
+;;  terms of this license.  You must not remove this notice, or any other,
+;;  from this software.
+;;
+;;  map_utils.clj
+;;
+;;  Utilities for operating on Clojure maps.
+;;
+;;  jason at w01fe dot com
+;;  Created 25 Feb 2009
+
+(ns clojure.contrib.map-utils)
+
+
+(defmacro lazy-get 
+  "Like get, but doesn't evaluate not-found unless it is needed."
+  [map key not-found]
+  `(if-let [pair# (find ~map ~key)] 
+       (val pair#)
+     ~not-found))
+
+(defn safe-get 
+  "Like get, but throws an exception if the key is not found."
+  [map key] 
+  (lazy-get map key 
+   (throw (IllegalArgumentException. (format "Key %s not found in %s" key map)))))
+
+(defn safe-get-in 
+  "Like get-in, but throws an exception if any key is not found."
+  [map ks]
+  (reduce safe-get map ks))
+
+