Data commit

Task/Entropy/CLU/entropy.clu

@@ -0,0 +1,29 @@
+% NOTE: when compiling with Portable CLU,
+% this program needs to be merged with 'useful.lib' to get log()
+%
+% pclu -merge $CLUHOME/lib/useful.lib -compile entropy.clu
+
+shannon = proc (s: string) returns (real)
+    % find the frequency of each character
+    freq: array[int] := array[int]$fill(0, 256, 0)
+    for c: char in string$chars(s) do
+        i: int := char$c2i(c)
+        freq[i] := freq[i] + 1
+    end
+
+    % calculate the component for each character
+    h: real := 0.0
+    rlen: real := real$i2r(string$size(s))
+    for i: int in array[int]$indexes(freq) do
+        if freq[i] ~= 0 then
+            f: real := real$i2r(freq[i]) / rlen
+            h := h - f * log(f) / log(2.0)
+        end
+    end
+    return (h)
+end shannon
+
+start_up = proc ()
+    po: stream := stream$primary_output()
+    stream$putl(po, f_form(shannon("1223334444"), 1, 6))
+end start_up