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Task/Average-loop-length/Phix/average-loop-length.phix

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+constant MAX = 20,
+         ITER = 1000000
+
+function expected(integer n)
+atom sum = 0
+    for i=1 to n do
+        sum += factorial(n) / power(n,i) / factorial(n-i)
+    end for
+    return sum
+end function
+
+function test(integer n)
+integer count = 0, x, bits
+    for i=1 to ITER do
+        x = 1
+        bits = 0
+        while not and_bits(bits,x) do
+            count += 1
+            bits = or_bits(bits,x)
+            x = power(2,rand(n)-1)
+        end while
+    end for
+    return count/ITER
+end function
+
+atom av, ex
+    puts(1," n     avg.     exp.  (error%)\n");
+    puts(1,"==   ======   ======  ========\n");
+    for n=1 to MAX do
+        av = test(n)
+        ex = expected(n)
+        printf(1,"%2d %8.4f %8.4f  (%5.3f%%)\n", {n,av,ex,abs(1-av/ex)*100})
+    end for