Support double random number generation in range [0,1).

Signed-off-by: Stefan Westerfeld <stefan@space.twc.de>

src/random.hh

@@ -23,6 +23,7 @@
 
 #include <vector>
 #include <string>
+#include <random>
 
 class Random
 {
@@ -41,6 +42,8 @@ private:
   std::vector<uint64_t>      buffer;
   size_t                     buffer_pos = 0;
 
+  std::uniform_real_distribution<double> double_dist;
+
   void die_on_error (const char *func, gcry_error_t error);
 public:
   Random (uint64_t seed, Stream stream);
@@ -54,6 +57,21 @@ public:
 
     return buffer[buffer_pos++];
   }
+  uint64_t
+  min() const
+  {
+    return 0;
+  }
+  uint64_t
+  max() const
+  {
+    return UINT64_MAX;
+  }
+  double
+  random_double() /* range [0,1) */
+  {
+    return double_dist (*this);
+  }
   void refill_buffer();
   void seed (uint64_t seed, Stream stream);
 

src/testrandom.cc

@@ -30,6 +30,8 @@ main (int argc, char **argv)
       uint64_t x = rng();
       printf ("%016lx\n", x);
     }
+  for (size_t i = 0; i < 20; i++)
+    printf ("%f\n", rng.random_double());
 
   uint64_t s = 0;
   double t_start = get_time();