runexec · August 16, 2017 22:11 · Sep 14, 2014 · Sep 13, 2014 · Sep 13, 2014
diff --git a/clojure-transduce-reduce.md b/clojure-transduce-reduce.md
@@ -117,7 +117,7 @@ Notes and examples of Transducers and Reducers
 
 ```
 
-* For lazy transformations you must use ```clojure sequence```
+* For lazy transformations you must use ```sequence```
 
 ```clojure
 

diff --git a/clojure-transduce-reduce.md b/clojure-transduce-reduce.md
@@ -117,3 +117,29 @@ Notes and examples of Transducers and Reducers
 
 ```
 
+* For lazy transformations you must use ```clojure sequence```
+
+```clojure
+
+(def star-wrap
+  (map #(str "*" % "*")))
+
+;=> #'user/star-wrap
+
+(into [] star-wrap [1 2 3])
+
+;=> ["*1*" "*2*" "*3*"]
+
+(sequence star-wrap [1 2 3])
+
+;=> ("*1*" "*2*" "*3*")
+
+(type (into [] star-wrap [1 2 3]))
+
+;=> clojure.lang.PersistentVector
+
+(type (sequence star-wrap [1 2 3]))
+
+;=> clojure.lang.LazyTransformer
+
+```
diff --git a/clojure-transduce-reduce.md b/clojure-transduce-reduce.md
@@ -0,0 +1,119 @@
+## Transducers and Reducers
+
+Notes and examples of Transducers and Reducers
+
+### Reducers
+
+* Used on collections 
+
+* Eager evaluation only. (not lazy)
+
+* The operation(s) and the input are no longer tied together
+
+```clojure
+
+(r/map zero?)
+
+;=> #<reducers$map$fn__2527 clojure.core.reducers$map$fn__2527@7201f000>
+
+(let [map-zero? (r/map zero?)
+      inputs [0 1 0 1 0 1]]
+  (reduce conj [] (map-zero? inputs)))
+
+;=> [true false true false true false]
+
+```
+* Can be combined into a single function for better performance. (composable)
+
+```clojure
+
+(def zero?-and-not-false 
+  (comp 
+   (r/filter true?)
+   (r/map zero?)))     
+
+;=> #'user/zero?-and-not-false
+
+(reduce conj [] (zero?-and-not-false [0 1 0 1 0 1]))
+
+[true true true]
+
+```
+
+### Transducers
+
+* Can be used in ClojureScript
+
+* Function C is the reducing function
+
+* Function B calls Function C
+
+* Function A creates Function B
+
+* (A C) -> B
+
+
+```clojure
+
+(defn a [c]  
+  (fn b    
+    ([] (c))    
+    ([coll] (c coll))    
+    ([coll input] (c coll input))))
+
+;=> #'user/a
+
+(transduce a + [1 2 3])
+
+;=> 6    
+
+```
+
+* Doesn't care about the input type
+
+* Transducers seem to be faster than reducers
+
+```clojure
+
+     (dotimes [n 5] (time (r/reduce + 0 [1 2 3])))
+
+     "Elapsed time: 0.23142 msecs"
+     "Elapsed time: 0.047252 msecs"
+     "Elapsed time: 0.043944 msecs"
+     "Elapsed time: 0.062372 msecs"
+     "Elapsed time: 0.05938 msecs"
+
+     ;=> nil
+
+     (dotimes [n 5] (time (transduce a + 0 [1 2 3])))
+
+     "Elapsed time: 0.1257 msecs"
+     "Elapsed time: 0.026548 msecs"
+     "Elapsed time: 0.018166 msecs"
+     "Elapsed time: 0.031276 msecs"
+     "Elapsed time: 0.024773 msecs"
+
+     ;=> nil
+```
+
+* Collection fns of previous Clojure versions are now optionally Transducers
+
+```clojure
+
+(let [*2 #(* % 2)
+      *4 #(* % 4)]
+
+  (def weird-composition       
+    (comp 
+     (filter even?)
+     (map *2)
+     (map *4))))
+
+;=> #'user/weird-composition
+
+(into [] weird-composition [1 2 3 4])
+
+;=> [16 32]
+
+```
+
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