Data commit

Task/Entropy/PicoLisp/entropy.l

@@ -0,0 +1,25 @@
+(scl 8)
+(load "@lib/math.l")
+
+(setq LN2 0.693147180559945309417)
+
+(de tabulate-chars (Str)
+   (let Map NIL
+      (for Ch (chop Str)
+         (if (assoc Ch Map)
+            (con @ (inc (cdr @)))
+            (setq Map (cons (cons Ch 1) Map))))
+   Map))
+
+(de entropy (Str)
+   (let (
+      Sz    (length Str)
+      Hist  (tabulate-chars Str)
+   )
+   (*/
+      (sum
+         '((Pair)
+            (let R (*/ (cdr Pair) 1. Sz)
+               (- (*/ R (log R) 1.))))
+         Hist)
+      1. LN2)))