I started my discussion about the  "Automatic Return Type (C++98)" in my last post. Today, I'm faced with the same challenge but solve it with C++11, C++14, and C++20.

Depending on the used C++ standard, there are different ways to return the right return type of a function template. In this post, I start with traits (C++98), continue in my next post with C++11/14, and end with concepts (C++20).

A dependent name is essentially a name that depends on a template parameter. A dependent name can be a type, a non-type, or a template parameter. To express that a dependent name stands for a type or a template, you have to use the keywords typename or template.

A friend has unrestricted access to the members of a class. Consequently, friendship should be given wisely. Regarding templates, friendship is special.

Typically, you use the overload pattern for a std::variant. std::variant is a type-safe union. A std::variant (C++17) has one value from one of its types. std::visit allows you to apply a visitor to it. Exactly here comes the overload pattern very handy into play.

To complete my post about variadic templates and fold expressions, I present in this post smart tricks using parameter packs and fold expressions.

I have prepared the pdf bundle. To get it is quite simple.

In my last two posts "Variadic Templates or the Power of Three Dots" and "More about Variadic Templates", I introduced variadic templates. This post goes one step further in the future and presents fold expressions that can directly reduce a parameter pack with a binary operator. 

Get all my books about modern C++ in one bundle.

In the last weeks; I learned something new about modules in C++20: private modules fragments and header units. Consequently, I make a short detour in this post and present these new features.