Add a bunch of new languages

Task/Entropy/R/entropy.r

@@ -0,0 +1,5 @@
+entropy = function(s)
+   {freq = prop.table(table(strsplit(s, '')[1]))
+    -sum(freq * log(freq, base = 2))}
+
+print(entropy("1223334444"))   # 1.846439

Task/Entropy/Racket/entropy.rkt

@@ -0,0 +1,17 @@
+#lang racket
+(require math)
+
+(define (log2 x)
+  (/ (log x) (log 2)))
+
+(define (digits x)
+  (for/list ([c (number->string x)])
+    (- (char->integer c) (char->integer #\0))))
+
+(define (entropy x)
+  (define ds (digits x))
+  (define n (length ds))
+  (- (for/sum ([(d c) (in-hash (samples->hash ds))])
+       (* (/ d n) (log2 (/ d n))))))
+
+(entropy 1223334444)