C++Now 2019

Most modern languages treat functions as first-class citizens, and Modern C++ is no different. The introduction of lambda expressions and utilities such as `std::function` enable countless functional programming patterns that can increase the flexibility and safety of APIs, and help reduce code repetition on the implementation side.

In this talk we're going to see examples of how higher-order functions can be used in practice to increase the quality of production code and the productivity of developers. A new abstraction proposed to the Standard Library for C++20, `function_ref`, will also be covered and compared to other techniques for the implementation of higher-order functions. `function_ref` is a lightweight wrapper over any `Callable` with a given signature that is easy for the compiler to optimize and inline.

This presentation will go over the specification and implementation of `function_ref`, also covering potential future extensions.