March 2014 update

Task/Entropy/CoffeeScript/entropy.coffee

@@ -0,0 +1,13 @@
+entropy = (s) ->
+    freq = (s) ->
+        result = {}
+        for ch in s.split ""
+            result[ch] ?= 0
+            result[ch]++
+        return result
+
+    frq = freq s
+    n = s.length
+    ((frq[f]/n for f of frq).reduce ((e, p) -> e - p * Math.log(p)), 0) * Math.LOG2E
+
+console.log "The entropy of the string '1223334444' is #{entropy '1223334444'}"