Add returning object reference

Replace Perfect Forwarding with retuning reference to an object as
this is the more often used case needed in a refcard.

Author: legends2k

cpp_param_ref.org

@@ -204,51 +204,55 @@ void Deduce(doc::Properties& p) {
 }
 #+END_SRC
 
-* ~In Out~
+* ~Out~ Object Reference
 
 #+BEGIN_EXPORT latex
-\invisible{hi}\vspace{-2em}  % remove unnecessary vspace due to minted
-\hfill\begin{tabular}{@{}p{0.4\linewidth}@{}}  % align horizontally in page
-\vspace{-3em}  % align vertically with section title
+\invisible{hi}\vspace{-1.5em}
+\hfill\begin{tabular}{@{}p{0.4\linewidth}@{}}
+    \vspace{-3em}
 #+END_EXPORT
 
 #+BEGIN_SRC c++
-void f(T&);
+      T& f();
+const T& f();
 #+END_SRC
 
 #+LATEX: \end{tabular}
 
-Objects for /reading/ and /writing/: *lvalue reference*
+Return *lvalue reference* to /object outliving function and caller/
 
 #+BEGIN_SRC c++
 // example
-void AdjustMargins(std::vector<Margin>& margins) {
-}
+struct Application {
+  Document& GetDocument { return m_pdf; }  // covariant return type
+  PDFDocument m_pdf;
+};  // app outlives GetDocument() and temp() calls
+void PrintDoc(Application& app) { app.GetDocument().Print(); }
+int main() { Application app{str_pdf_path}; PrintDoc(app); }
 #+END_SRC
 
-* Perfect Forwarding
+* ~In Out~
 
 #+BEGIN_EXPORT latex
-\invisible{hi}\vspace{-1.5em}
-\hfill\begin{tabular}{@{}p{0.4\linewidth}@{}}
-    \vspace{-3em}
+\invisible{hi}\vspace{-2em}  % remove unnecessary vspace due to minted
+\hfill\begin{tabular}{@{}p{0.4\linewidth}@{}}  % align horizontally in page
+\vspace{-3em}  % align vertically with section title
 #+END_EXPORT
 
 #+BEGIN_SRC c++
-template <typename T>
-void f(T&&);
+void f(T&);
 #+END_SRC
 
 #+LATEX: \end{tabular}
 
-Pass parameter retaining lvalue/rvalue-/ness/: *forwarding reference*
+Objects for /reading/ and /writing/: *lvalue reference*
 
 #+BEGIN_SRC c++
-template <typename T>
-void SetTiel(T&& title) {
-  internal::SetTitle(std::forward<T>(title));
+// example
+void AdjustMargins(std::vector<Margin>& margins) {
 }
 #+END_SRC
 
+
 #+LATEX: \vspace{0.75em}
 *Reference*: [[https://github.com/CppCon/CppCon2014/blob/master/Presentations/Back%2520to%2520the%2520Basics!%2520Essentials%2520of%2520Modern%2520C%252B%252B%2520Style/Back%2520to%2520the%2520Basics!%2520Essentials%2520of%2520Modern%2520C%252B%252B%2520Style%2520-%2520Herb%2520Sutter%2520-%2520CppCon%25202014.pdf][Essentials of Modern C++ Style, /Herb Sutter/]]