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Task/Fibonacci-word/D/fibonacci-word.d

@@ -0,0 +1,23 @@
+import std.stdio, std.algorithm, std.math, std.string, std.range;
+
+real entropy(T)(T[] s) pure nothrow
+if (__traits(compiles, s.sort())) {
+    immutable sLen = s.length;
+    return s
+           .sort()
+           .group
+           .map!(g => g[1] / real(sLen))
+           .map!(p => -p * p.log2)
+           .sum;
+}
+
+void main() {
+    enum uint nMax = 37;
+
+    "  N     Length               Entropy Fibword".writeln;
+    uint n = 1;
+    foreach (s; recurrence!q{a[n - 1] ~ a[n - 2]}("1", "0").take(nMax))
+        writefln("%3d %10d %2.19f %s", n++, s.length,
+                 s.dup.representation.entropy.abs,
+                 s.length < 25 ? s : "<too long>");
+}