diff --git a/triqs/mc_tools/generator.hpp b/triqs/mc_tools/generator.hpp
index 7b076139..6e29c38d 100644
--- a/triqs/mc_tools/generator.hpp
+++ b/triqs/mc_tools/generator.hpp
@@ -33,7 +33,13 @@ namespace boost{
                     buf->fill();
                 return *cur++;
             }
-            generator(generator<R> const & rhs)
+            inline R const preview() {
+                if (cur == end)
+                    buf->fill();
+                return *cur;
+            }
+
+	     generator(generator<R> const & rhs)
                 : 
                  buf(new buffer (*rhs.buf))
                 , cur(buf->cur)
diff --git a/triqs/mc_tools/random_generator.hpp b/triqs/mc_tools/random_generator.hpp
index 79107f13..f3c75557 100644
--- a/triqs/mc_tools/random_generator.hpp
+++ b/triqs/mc_tools/random_generator.hpp
@@ -59,6 +59,9 @@ namespace mc_tools {
   INTEGER_OVERLOAD(size_t)
 #undef INTEGER_OVERLOAD
 
+  /// Returns a double in [0,1[ with flat distribution
+  double preview() { return gen->preview();} 
+
   /// Returns a double in [0,1[ with flat distribution
   double operator()() { return ((*gen)());}