1 files changed, 69 insertions, 0 deletions
diff --git a/src/common/random.hpp b/src/common/random.hpp
new file mode 100644
index 0000000..44057ed
--- /dev/null
+++ b/src/common/random.hpp
@@ -0,0 +1,69 @@
+#ifndef RANDOM_HPP
+#define RANDOM_HPP
+
+# include "random.t.hpp"
+
+# include "sanity.hpp"
+
+# include <random>
+
+// This is not namespace random since that collides with a C function,
+// but this can be revisited when everything goes into namespace tmwa.
+namespace random_
+{
+    /// Get a random number from 0 .. 2**32 - 1
+    extern std::mt19937 generate;
+
+    /// Get a random number from 0 .. bound - 1
+    inline
+    int to(int bound)
+    {
+        std::uniform_int_distribution<int> dist(0, bound - 1);
+        return dist(generate);
+    }
+
+    /// Get a random number from low .. high (inclusive!)
+    inline
+    int in(int low, int high)
+    {
+        std::uniform_int_distribution<int> dist(low, high);
+        return dist(generate);
+    }
+
+    inline
+    bool coin()
+    {
+        // sigh, can't specify <bool> directly ...
+        std::uniform_int_distribution<int> dist(false, true);
+        return dist(generate);
+    }
+
+    inline
+    bool chance(Fraction f)
+    {
+        if (f.num <= 0)
+            return false;
+        if (f.num >= f.den)
+            return true;
+        return random_::to(f.den) < f.num;
+    }
+
+    // C is usually one of:
+    //  std::vector<T>
+    //  std::initializer_list<T>
+    //  std::array<T, n>
+    template<class C>
+    auto choice(C&& c) -> decltype(*c.begin())
+    {
+        return *(c.begin() + random_::to(c.size()));
+    }
+
+    // allow bare braces
+    template<class T>
+    T choice(std::initializer_list<T>&& il)
+    {
+        return random_::choice(il);
+    }
+} // namespace random_
+
+#endif // RANDOM_HPP