4.4. Using synchronization of operations to simplify code

Using the synchronization facilities described so far in this chapter as building blocks allows you to focus on the operations that need synchronizing rather than the mechanics. One way this can help simplify your code is that it accommodates a much more functional (in the sense of functional programming) approach to programming concurrency. Rather than sharing data directly between threads, each task can be provided with the data it needs, and the result can be disseminated to any other threads that need it through the use of futures.

4.4.1. Functional programming with futures

The term functional programming (FP) refers to a style of programming where the result of a function call depends solely on the parameters to that function and doesn’t depend on any external state. This is related to the mathematical concept of a function, and it means that if you invoke a function twice with the same parameters, the result is exactly the same. This is a property of many of the mathematical functions in the C++ Standard Library, such as sin, cos, and sqrt, and simple operations on basic types, such as 3+3, 6*9, or 1.3/4.7. A pure function doesn’t modify any external state either; the effects of the function are entirely limited to the return value.