Type Traits

Template metaprogramming #

Template metaprogramming is programming at compile-time. However, what does template metaprogramming have in common with the type-traits library? As it turns out, quite a lot! The type-traits library is pure template metaprogramming enclosed in a library.

Applications of template metaprogramming #

• Programming at compile-time.
• Programming with types such as double or int and not with values such as 5.5 or 5.
• The compiler instantiates the templates and generates C++ code.

Type traits: goals #

The type traits library requires the following header:

#include <type_traits>

Looking carefully, we can see that type traits have a big optimization potential. In the first step, the type traits analyze the code at compile-time, and in the second step, they optimize the code based on that analysis. How is that possible? Depending on the type of the variable, a faster variant of an algorithm will be chosen.

Optimization #

• An optimized version of std::copy, std::fill, or std::equal is used so the algorithms can work on memory blocks.

Correctness #

• Type checks will be performed at compile-time.
• Together with static_assert, the type information defines the requirements for the code.