add tests for distribution utility and fix loose ends

src/test/distribution.cpp

@@ -0,0 +1,45 @@
+/*++
+Copyright (c) 2023 Microsoft Corporation
+
+Module Name:
+
+    distribution.cpp
+
+Abstract:
+
+    Test distribution
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2023-04-13
+
+
+--*/
+#include "util/distribution.h"
+#include <iostream>
+
+static void tst1() {
+    distribution dist(1);
+    dist.push(1, 3);
+    dist.push(2, 1);
+    dist.push(3, 1);
+    dist.push(4, 1);
+
+    unsigned counts[4] = { 0, 0, 0, 0 };
+    for (unsigned i = 0; i < 1000; ++i)
+        counts[dist.choose()-1]++;
+    for (unsigned i = 1; i <= 4; ++i)
+        std::cout << "count " << i << ": " << counts[i-1] << "\n";
+
+    for (unsigned i = 0; i < 5; ++i) {
+        std::cout << "enum ";
+        for (auto j : dist)
+            std::cout << j << " ";
+        std::cout << "\n";
+    }
+
+}
+
+void tst_distribution() {
+    tst1();
+}