avoid multi-line log messages

src/ds/str.h

@@ -123,17 +123,9 @@ struct StrReflect : boost::noncopyable {
 template <typename T>
 struct Str<T, typename std::enable_if<ds::reflector<T>::is_defined::value>::type> {
   static inline void f(std::ostream& ostream, const T& x, int indent) {
-    // \n at the start and at the end of struct seem like good compromise
-    // between readability, consumed vertical space and code complexity
-    ostream << "(\n";
-    for (int i = 0; i < indent; i++) {
-      ostream << "  ";
-    }
+    ostream << "{";
     ds::reflector<T>::visit(StrReflect<T>(ostream, x, indent));
-    ostream << ")\n";
-    for (int i = 0; i < indent - 1; i++) {
-      ostream << "  ";
-    }
+    ostream << "}";
   }
 };