Templates reducing the runtime 
In this section, we will continue our discussion on removing or minimizing runtime decisions on the critical or hot path by introducing another important C++ feature. We will discuss what templates are, the motivation for using them, their advantages and disadvantages, and their performance relative to the alternatives.
What are templates?
Templates are the C++ mechanism to implement generic functions and classes. Generic programming is when generic types are used as arguments in algorithms and classes for compatibility with different data types. This eliminates code duplication and the need to repeatedly write similar or shared code that is independent of data type. Templates not only work with different data types, but based on what different types are needed at compile time, the source code for the classes and methods for those data types is generated automatically at compile time, just as with C macros. Unlike macros, however, the compiler...