Google groups files section is having issues.
Here's 'reduction' as discussed in IRC, mostly written by Rich.
--Chouser
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diff --git a/src/clj/clojure/core.clj b/src/clj/clojure/core.clj
index 4aad594..a027e00 100644
--- a/src/clj/clojure/core.clj
+++ b/src/clj/clojure/core.clj
@@ -535,7 +535,20 @@
"Returns a seq of the items in coll in reverse order. Not lazy."
[coll]
(reduce conj nil coll))
-
+
+(defn reduction
+ "Returns a lazy seq of the intermediate values of the reduction (as
+ per reduce) of coll by f, starting with init."
+ ([f [x & xs :as coll]]
+ (when (seq coll)
+ (if-let [[x2 & xs2] xs]
+ (reduction f (f x x2) xs2)
+ (cons x nil))))
+ ([f init [x & xs :as coll]]
+ (if (seq coll)
+ (lazy-cons init (reduction f (f init x) xs))
+ (cons init nil))))
+
;;math stuff
(defn +
"Returns the sum of nums. (+) returns 0."
