diff --git a/package.lisp b/package.lisp
index 8d3e3bc..78045fa 100644
--- a/package.lisp
+++ b/package.lisp
@@ -22,11 +22,7 @@
 
 (defpackage :data-lens.transducers.internals
   (:use :cl)
-  (:export
-   #:unwrap
-   #:init
-   #:reduce-generic
-   #:stepper))
+  (:export #:unwrap #:init #:reduce-generic #:stepper))
 
 (defpackage :data-lens.transducers
   (:use :cl)
@@ -35,13 +31,7 @@
   (:export #:mapping :filtering :deduping :catting :splitting
            #:exit-early :taking :dropping :transduce
            #:hash-table-builder :vector-builder :list-builder
-           #:mv-mapping
-           #:mv-selecting
-           #:hash-table-select
-           #:mv-filtering
-           #:lazy-sequence
-           #:compressing-runs
-           #:mapcatting
-           #:iota
-           #:repeating
-           #:repeating*))
+           #:collecting #:mv-mapping #:mv-selecting
+           #:hash-table-select #:mv-filtering #:mapcatting
+           #:lazy-sequence #:compressing-runs #:iota
+           #:repeating #:repeating*))
diff --git a/t/transducer.lisp b/t/transducer.lisp
index 1112076..952f4de 100644
--- a/t/transducer.lisp
+++ b/t/transducer.lisp
@@ -107,6 +107,16 @@
              (2 4 4 4) (2 5 5 5)
              (3 6 6 6))))))
 
+(5am:def-test collecting (:suite :data-lens.transducers)
+  (5am:is (equal '(1 3 6 9 13 18 22 27 33 40)
+                 (data-lens.transducers:transduce (data-lens:• (data-lens.transducers:taking 5)
+                                                               (data-lens.transducers:mapcatting 'identity)
+                                                               (data-lens.transducers::collecting '+))
+                                                  'data-lens.transducers:list-builder
+                                                  (loop for x from 1
+                                                        repeat 4
+                                                        collect (data-lens.transducers:iota :start x :count x))))))
+
 (5am:def-test catting (:suite :data-lens.transducers)
   (5am:is (equal '(1 1 2 1 2 2 3 3 4 1)
                  (data-lens.transducers:transduce (data-lens.transducers:catting)
@@ -117,7 +127,13 @@
   (5am:is (equal '(1 1 2 1 2 2 3 3 4 1)
                  (data-lens.transducers:transduce (data-lens.transducers:mapcatting 'list)
                                                   'data-lens.transducers:list-builder
-                                                  '(1 1 2 1 2 2 3 3 4 1)))))
+                                                  '(1 1 2 1 2 2 3 3 4 1))))
+  (5am:is (equal '(0 0 1 0 1 2)
+                 (data-lens.transducers:transduce (data-lens.transducers:mapcatting 'identity)
+                                                  'data-lens.transducers:list-builder
+                                                  (list (data-lens.transducers:iota :count 1)
+                                                        (data-lens.transducers:iota :count 2)
+                                                        (data-lens.transducers:iota :count 3))))))
 
 (5am:def-test splitting (:suite :data-lens.transducers)
   (5am:is (equal '((2 0) (3 1) (4 2))
@@ -125,7 +141,6 @@
                                                   'data-lens.transducers:list-builder
                                                   '(1 2 3)))))
 
-
 (5am:def-test transducer-composition (:suite :data-lens.transducers)
   (5am:is (equal '(3 5 7)
                  (data-lens.transducers:transduce (data-lens:•
diff --git a/transducers.lisp b/transducers.lisp
index 18b8bb3..eee9581 100644
--- a/transducers.lisp
+++ b/transducers.lisp
@@ -86,6 +86,18 @@
                       (funcall rf it last)
                       it)))))))
 
+
+(defun collecting (collector)
+  (lambda (rf)
+    (let (sofar)
+      (transducer-lambda
+        ((acc next)
+         (if sofar
+             (setf sofar (funcall collector sofar next))
+             (setf sofar next))
+         (funcall rf acc sofar))))))
+
+
 (defun deduping (&optional (test 'eql))
   (compressing-runs :test test))