mattdenner · December 18, 2015 17:09 · Jun 19, 2013 · Jun 19, 2013
diff --git a/attempt1.clj b/attempt1.clj
@@ -1,4 +1,6 @@
-; My first attempt would have been my typical approach: wrap the function being used in the map.
+; My first attempt would have been my typical approach: wrap the function being used in the map.  What I dislike, even though
+; this is my current natural (read "first thing I try normally") is that 'reporter' looks more complicated than I'd like, plus
+; 'report-progress' knows about the idea of "progress".
 (defn reporter
   [report-every f]
   (fn [val cnt]

diff --git a/attempt2.clj b/attempt2.clj
@@ -12,6 +12,13 @@
   [aseq reporter]
   (map-indexed (fn [& args] (apply reporter args) (last args)) aseq))
 
+; Here 'report-progress' knows only about mapping, really, and so this function doesn't have to exist:
+;   (doall (map identity (reporting-seq (range 10) (progress-reporter 2))))
+;
+; Which then leads to:
+;   (doall (map identity (reporting-seq (range 10) (fn [cnt val] (println "Processing:" val)))))
+;
+; Which has nothing to do with progress!
 (defn report-progress
   [report-every aseq]
   (map identity (reporting-seq aseq (progress-reporter report-every))))

diff --git a/attempt1.clj b/attempt1.clj
@@ -0,0 +1,16 @@
+; My first attempt would have been my typical approach: wrap the function being used in the map.
+(defn reporter
+  [report-every f]
+  (fn [val cnt]
+    (let [rv (f val)]
+      (and (zero? (mod cnt report-every)) (println "Done" cnt))
+      val)
+    ))
+
+(defn report-progress
+  [report-every aseq]
+  (map (reporter report-every identity)
+       aseq
+       (iterate inc 1)))
+
+(doall (report-progress 2 (range 10)))
diff --git a/attempt2.clj b/attempt2.clj
@@ -0,0 +1,19 @@
+; Then I read the popular answer (http://stackoverflow.com/a/2023356/207031) which talks about wrapping the *data*.  At the
+; moment this is my favourite, and it's taught me a lot, because it cleanly separates so much of the behaviour.
+(defn progress-reporter
+  "Returns a function that reports the count every 'report-every' times"
+  [report-every]
+  (fn [cnt _]
+    (and (zero? (mod cnt report-every)) (println "Done" cnt))))
+
+(defn reporting-seq
+  "Wraps a sequence so that the 'reporter' function is called with the index and value for reporting, but maintains map
+  behaviour of the inner sequence"
+  [aseq reporter]
+  (map-indexed (fn [& args] (apply reporter args) (last args)) aseq))
+
+(defn report-progress
+  [report-every aseq]
+  (map identity (reporting-seq aseq (progress-reporter report-every))))
+
+(doall (report-progress 2 (range 10)))
diff --git a/original.clj b/original.clj
@@ -0,0 +1,15 @@
+; Here's the original code:
+(defn report
+  [report-every val cnt]
+  (if (= 0 (mod cnt report-every))
+     (println "Done" cnt))
+  val)
+
+(defn report-progress
+  [report-every aseq]
+  (map (fn [val cnt]
+          (report report-every val cnt))
+       aseq
+       (iterate inc 1)))
+
+(doall (report-progress 2 (range 10)))
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