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diff --git a/src/clojure/contrib/print_json.clj b/src/clojure/contrib/print_json.clj
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+;;; print_json.clj: JavaScript Object Notation (JSON) generator
+
+;; by Stuart Sierra, http://stuartsierra.com/
+;; January 26, 2009
+
+;; Copyright (c) Stuart Sierra, 2009. 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.
+
+
+
+;; For more information on JSON, see http://www.json.org/
+
+
+
+(ns clojure.contrib.print-json
+  (:use [clojure.contrib.test-is :only (deftest is)]))
+
+(defmulti
+  #^{:doc "Prints Clojure data types as JSON.  Nil becomes JSON null.
+  Keywords become strings, without the leading colon.  Maps become
+  JSON objects, all other collection types become JSON arrays.
+  Strings and numbers print as with pr."}
+  print-json (fn [x]
+               (cond (nil? x) nil
+                     (map? x) :object
+                     (coll? x) :array
+                     (keyword? x) :keyword
+                     :else :default)))
+
+(defmethod print-json :default [x] (pr x))
+
+(defmethod print-json nil [x] (print "null"))
+
+(defmethod print-json :keyword [x] (pr (name x)))
+
+(defmethod print-json :array [s]
+  (print "[")
+  (loop [x s]
+    (when (first x)
+      (print-json (first x))
+      (when (rest x)
+        (print ",")
+        (recur (rest x)))))
+  (print "]"))
+
+(defmethod print-json :object [m]
+  (print "{")
+  (loop [x m]
+    (when (first x)
+      (let [[k v] (first x)]
+        (print-json k)
+        (print ":")
+        (print-json v))
+      (when (rest x)
+        (print ",")
+        (recur (rest x)))))
+  (print "}"))
+
+(defn json-str
+  "Converts Clojure data structures to a JSON-formatted string."
+  [x]
+  (with-out-str (print-json x)))
+
+
+
+;;; TESTS
+
+;; Run these tests with
+;; (clojure.contrib.test-is/run-tests 'clojure.contrib.print-json)
+
+;; Bind clojure.contrib.test-is/*load-tests* to false to omit these
+;; tests from production code.
+
+(deftest can-print-json-strings
+  (is (= "\"Hello, World!\"" (json-str "Hello, World!")))
+  (is (= "\"\\\"Embedded\\\" Quotes\"" (json-str "\"Embedded\" Quotes"))))
+
+(deftest can-print-json-null
+  (is (= "null" (json-str nil))))
+
+(deftest can-print-json-arrays
+  (is (= "[1,2,3]" (json-str [1 2 3])))
+  (is (= "[1,2,3]" (json-str (list 1 2 3))))
+  (is (= "[1,2,3]" (json-str (sorted-set 1 2 3))))
+  (is (= "[1,2,3]" (json-str (seq [1 2 3])))))
+
+(deftest can-print-empty-arrays
+  (is (= "[]" (json-str [])))
+  (is (= "[]" (json-str (list))))
+  (is (= "[]" (json-str #{}))))
+
+(deftest can-print-json-objects
+  (is (= "{\"a\":1,\"b\":2}" (json-str (sorted-map :a 1 :b 2)))))
+
+(deftest can-print-empty-objects
+  (is (= "{}" (json-str {}))))