format print "Writing tree for generation"

src/libaevol/7/ExpManager_7.cpp

@@ -2915,9 +2915,10 @@ for (size_t index = 0; index < mutant_list_.size(); index++) {
                                                       previous_individuals);
 
         if (AeTime::time() % exp_m_->backup_step() == 0) {
-          std::cout << "writing light tree for gen : " << AeTime::time()
-                    << '\n';
+          std::cout << "  Writing light tree for generation " << AeTime::time() << "...";
+          std::cout.flush();
           exp_m_->output_m()->write_light_tree(AeTime::time());
+          std::cout << " OK" << std::endl;
         }
       }
 
@@ -2932,9 +2933,10 @@ for (size_t index = 0; index < mutant_list_.size(); index++) {
         char tree_file_name[50];
 
         sprintf(tree_file_name, "tree/tree_" TIMESTEP_FORMAT ".ae", AeTime::time());
-std::cout << "writing 7777 tree for gen : " << AeTime::time()
-                    << '\n';
+        std::cout << "  Writing tree for generation " << AeTime::time() << "...";
+        std::cout.flush();
         exp_m_->output_m()->tree()->write_to_tree_file(tree_file_name);
+        std::cout << " OK" << std::endl;
       }
     }