Move-only types can save the API - Video

Video from Italian C++ Community
Event page: https://italiancpp.org/itcppcon20

About the talk
C++ is a language celebrated for its abstraction mechanisms that do not incur performance penalties at runtime. It is often used in many mission critical systems, games, and everywhere else where speed and safety are paramount.

That does not mean all C++ programs are fast by default. One of the most time costly mistakes we can make in C++ is creating unnecessary copies. C++11 move semantics made a move into the right direction. The move semantics allow us to give away data that we no longer want to use to somebody else without the penalty of creating the copy and without the risk of data races due to data being shared between multiple entities.

But, while generally cheaper than copying, moving is still not a free operation. For this reason, many people diss on the FP-style APIs as inefficient and create impure stateful APIs instead.

We are going to cover “linear types” – an idea from Phil Wadler that was meant to simplify and optimize pure GC-based languages such as Haskell. We’re going to show how the same concept that allows pure functional programming languages to efficiently “change the world” can improve software written in a traditionally imperative impure language such as C++. We will show that with linear types, the FP-style APIs do not need to be inherently slower than their impure imperative counterparts.