Mastering Functional Programming

Inversion of control

Since a computation expressed in terms of IO is not executed immediately but is merely stored as a description of a computation, it is possible to execute the computation against different execution strategies. For example, you may want to run the computation against various concurrent backends, each with its own concurrency strategies. You may want to run a competition synchronously or asynchronously. Later in this chapter, we will see how exactly this is done.