diff --git a/README.md b/README.md
index 978a7e6..8014e05 100644
--- a/README.md
+++ b/README.md
@@ -5,14 +5,14 @@ More transducers and reducing functions for Clojure(script)!
 [![Build Status](https://travis-ci.org/cgrand/xforms.png?branch=master)](https://travis-ci.org/cgrand/xforms)
 
 *Transducers* can be classified in three groups: regular ones, higher-order ones
-(which accept other transducers as arguments) and 1-item ones which emit only 1 item out no matter how many went in.
-1-item transducers generally only make sense in the context of a higher-order transducer. 
+(which accept other transducers as arguments) and aggrerators (transdcuers which emit only 1 item out no matter how many went in).
+Aggregators generally only make sense in the context of a higher-order transducer. 
 
 In `net.cgrand.xforms`:
 
- * regular ones: `partition` (1 arg), `reductions`, `for`, `take-last`, `drop-last`, `sort`, `sort-by`, `window` and `window-by-time`
+ * regular ones: `partition` (1 arg), `reductions`, `for`, `take-last`, `drop-last`, `sort`, `sort-by`, `wrap`, `window` and `window-by-time`
  * higher-order ones: `by-key`, `into-by-key`, `multiplex`, `transjuxt`, `partition` (2+ args)
- * 1-item ones: `reduce`, `into`, `without`, `transjuxt`, `last`, `count`, `avg`, `sd`, `min`, `minimum`, `max`, `maximum`, `str`
+ * aggregators: `reduce`, `into`, `without`, `transjuxt`, `last`, `count`, `avg`, `sd`, `min`, `minimum`, `max`, `maximum`, `str`
 
 In `net.cgrand.xforms.io`:
  * `sh` to use any process as a transducer
@@ -27,7 +27,7 @@ In `net.cgrand.xforms.io`:
 
 *Transducing contexts*:
 
- * in `net.cgrand.xforms`: `transjuxt` (for performing several transductions in a single pass), `iterator` (clojure only), `into`, `without`, `count` and `some`.
+ * in `net.cgrand.xforms`: `transjuxt` (for performing several transductions in a single pass), `iterator` (clojure only), `into`, `without`, `count`, `str` (2 args) and `some`.
  * in `net.cgrand.xforms.io`: `line-out` (3+ args) and `edn-out` (3+ args).
  * in `net.cgrand.xforms.nodejs.stream`: `transformer`.
 
@@ -40,7 +40,7 @@ In `net.cgrand.xforms.io`:
 Add this dependency to your project:
 
 ```clj
-[net.cgrand/xforms "0.15.0"]
+[net.cgrand/xforms "0.16.0"]
 ```
 
 ```clj
@@ -151,7 +151,7 @@ It's worth noting that all transformed outputs are subsequently interleaved. See
 ([false 0] [true 1] [false 2] [true 3] [false 4] [true 5] [false 6] [true 7])
 ```
 
-That's why most of the time the last stage of the sub-transducer will be a 1-item transducer like `x/reduce` or `x/into`:
+That's why most of the time the last stage of the sub-transducer will be an aggregator like `x/reduce` or `x/into`:
 
 ```clj
 => (sequence (x/partition 2 1 (x/into [])) (range 8))
diff --git a/package.json b/package.json
index 278e579..333f845 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "xforms",
-  "version": "0.15.0",
+  "version": "0.16.0",
   "description": "Extra transducers for Clojurescript",
   "repository": "https://github.com/cgrand/xforms.git",
   "author": "Christophe Grand <christophe@cgrand.net>",
diff --git a/project.clj b/project.clj
index f074ab6..52dc12a 100644
--- a/project.clj
+++ b/project.clj
@@ -1,4 +1,4 @@
-(defproject net.cgrand/xforms "0.15.0"
+(defproject net.cgrand/xforms "0.16.0"
   :description "Extra transducers for Clojure"
   :url "https://github.com/cgrand/xforms"
   :license {:name "Eclipse Public License"
diff --git a/src/net/cgrand/xforms.cljc b/src/net/cgrand/xforms.cljc
index b496934..cff5409 100644
--- a/src/net/cgrand/xforms.cljc
+++ b/src/net/cgrand/xforms.cljc
@@ -248,7 +248,34 @@
 
 (def max (reduce rf/max))
 
-(def str (reduce rf/str))
+(defn str
+  "When used as a value, it's an aggregating transducer that concatenates input values
+   into a single output value. 
+   When used as a function of two args (xform and coll) it's a transducing context that
+   concatenates all values in a string."
+  {:arglists '([xform coll])}
+  ([rf] ((reduce rf/str) rf))
+  ([xform coll]
+    (transduce xform rf/str coll)))
+
+(defn wrap
+  "Transducer. Adds open as the first item, and close as the last. Optionally inserts delim between each input item."
+  ([open close]
+    (fn [rf]
+      (let [vrf (volatile! nil)]
+        (vreset! vrf
+          (fn [acc x]
+            (let [acc (rf acc open)]
+              (vreset! vrf rf)
+              (if (reduced? acc)
+                acc
+                (rf acc x)))))
+        (fn
+          ([] (rf))
+          ([acc] (rf (unreduced (rf acc close))))
+          ([acc x] (@vrf acc x))))))
+  ([open close delim]
+    (comp (interpose delim) (wrap open close))))
 
 (defn vals [rf]
   (kvrf