add seq-utils/positions

3 files changed, 34 insertions, 1 deletions

diff --git a/src/clojure/contrib/seq_utils.clj b/src/clojure/contrib/seq_utils.clj
index d4c29c46..5f3b7446 100644
--- a/src/clojure/contrib/seq_utils.clj
+++ b/src/clojure/contrib/seq_utils.clj
@@ -211,3 +211,21 @@
                (cons (if (identical? x NIL) nil x)
                      (drain))))))))))
 
+(defmulti positions
+  "Returns a lazy sequence containing the positions at which item
+   is found in coll. Functions (responding true to fn?) are called
+   against members of the collection, other items are compared for
+   equality."
+  { :arglists '([item-or-pred coll]) }
+  (fn [item-or-pred _]
+    (if (fn? item-or-pred) :pred :item)))
+
+(defmethod positions :pred [pred coll]
+  (for [[idx elt] (indexed coll) :when (pred elt)] idx))
+
+(defmethod positions :item [item coll]
+  (for [[idx elt] (indexed coll) :when (= item elt)] idx))
+
+
+
+
diff --git a/src/clojure/contrib/test_contrib.clj b/src/clojure/contrib/test_contrib.clj
index 13498076..8402b7ba 100644
--- a/src/clojure/contrib/test_contrib.clj
+++ b/src/clojure/contrib/test_contrib.clj
@@ -20,7 +20,8 @@
      [:complex-numbers :fnmap :macro-utils :monads :pprint.pretty
       :pprint.cl-format :str-utils :shell-out :test-graph
       :test-dataflow :test-java-utils :test-lazy-seqs
-      :test-trace :test-jmx :java-utils :expect-test :expect-test.test-adapter-test])
+      :test-trace :test-jmx :java-utils :expect-test :expect-test.test-adapter-test
+      :seq-utils-test])
 
 (def test-namespaces
      (map #(symbol (str "clojure.contrib.test-contrib." (name %)))
diff --git a/src/clojure/contrib/test_contrib/seq_utils_test.clj b/src/clojure/contrib/test_contrib/seq_utils_test.clj
new file mode 100644
index 00000000..1de61cb5
--- /dev/null
+++ b/src/clojure/contrib/test_contrib/seq_utils_test.clj
@@ -0,0 +1,14 @@
+(ns clojure.contrib.test-contrib.seq-utils-test
+  (:use clojure.test
+	clojure.contrib.seq-utils))
+
+
+(deftest test-positions
+  (are [expected pred coll] (= expected (positions pred coll))
+       [1] nil [0 nil 5]
+       [1] nil? [0 nil 5]
+       () string? [:a :b :c]
+       [2] string? [:a :b "c"]
+       () :d [:a :b :c]
+       [0 2] :d [:d :a :d :a]))
+  
\ No newline at end of file