Replace mt_rand with <random>

Also add some utility methods and classes.

1 files changed, 74 insertions, 0 deletions

diff --git a/src/common/random2.hpp b/src/common/random2.hpp
new file mode 100644
index 0000000..86deddf
--- /dev/null
+++ b/src/common/random2.hpp
@@ -0,0 +1,74 @@
+#ifndef RANDOM2_HPP
+#define RANDOM2_HPP
+
+# include "random.hpp"
+# include "utils2.hpp"
+
+# include <algorithm>
+
+namespace random_
+{
+    namespace detail
+    {
+        struct RandomIterator
+        {
+            int bound;
+            int current;
+            bool frist;
+
+            void operator ++()
+            {
+                frist = false;
+                // TODO: reimplement in terms of LFSRs, so that certain
+                // blockage patterns don't favor adjacent cells.
+                current = current + 1;
+                if (current == bound)
+                    current = 0;
+            }
+            int operator *()
+            {
+                return current;
+            }
+        };
+
+        inline
+        bool operator == (RandomIterator l, RandomIterator r)
+        {
+            return l.current == r.current && l.frist == r.frist;
+        }
+
+        inline
+        bool operator != (RandomIterator l, RandomIterator r)
+        {
+            return !(l == r);
+        }
+    }
+
+    /// Yield every cell from 0 .. bound - 1 in some order.
+    /// The starting position is random, but not the order itself.
+    ///
+    /// Expected usage:
+    ///     for (int i : random_::iterator(vec.size()))
+    ///         if (vec[i].okay())
+    ///             return frob(vec[i]);
+    inline
+    IteratorPair<detail::RandomIterator> iterator(int bound)
+    {
+        int current = random_::to(bound);
+        return
+        {
+            detail::RandomIterator{bound, current, true},
+            detail::RandomIterator{bound, current, false}
+        };
+    }
+
+    /// similar to std::random_shuffle(c.begin(), c.end()), but guaranteed
+    /// to use a good source of randomness.
+    template<class C>
+    void shuffle(C&& c)
+    {
+        std::random_shuffle(c.begin(), c.end(), random_::to);
+    }
+} // namespace random_
+
+#endif // RANDOM2_HPP