June 2018 Update

Task/Unbias-a-random-generator/Elena/unbias-a-random-generator.elena

@@ -0,0 +1,45 @@
+import extensions.
+
+int extension $op
+{
+    bool randN
+        = randomGenerator nextInt(self) == 0.
+
+    bool unbiased
+    [
+        bool flip1 := self randN.
+        bool flip2 := self randN.
+
+        while (flip1 == flip2)
+        [
+            flip1 := self randN.
+            flip2 := self randN.
+        ].
+
+        ^ flip1
+    ]
+}
+
+program =
+[
+    3 to:6 do(:n)<int>
+    [
+        int biasedZero := 0.
+        int biasedOne := 0.
+        int unbiasedZero := 0.
+        int unbiasedOne := 0.
+
+        0 till:100000 do(:i)
+        [
+            if (n randN) [ biasedOne += 1 ]; [ biasedZero += 1 ].
+            if (n unbiased) [ unbiasedOne += 1 ]; [ unbiasedZero += 1 ]
+        ].
+
+        console
+            printLineFormatted("(N = {0}):" padRight(17) + "# of 0"$9"# of 1"$9"% of 0"$9"% of 1", n);
+            printLineFormatted("Biased:" padRight(15) + "{0}"$9"{1}"$9"{2}"$9"{3}",
+                                    biasedZero, biasedOne, biasedZero / 1000, biasedOne / 1000);
+            printLineFormatted("Unbiased:" padRight(15) + "{0}"$9"{1}"$9"{2}"$9"{3}",
+                                    unbiasedZero, unbiasedOne, unbiasedZero / 1000, unbiasedOne / 1000).
+    ]
+].