Because of this, when reasoning about the program we can replace these functions with the results of evaluating them, much like we can replace the expression 2 + 3 with the result 5 without changing the meaning when we are performing algebra.Because the important functions therein are pure, they will always return the same result given the same input.The pure core is called an “algebra” because operating therein we will maintain referential transparency: The algebras and runtime package structure of the ArrowKt Android app There are two root packages: algebra and runtime. This explains the first design choice of the ArrowKt sample app. We could call these impure functions the imperative shell around the pure “core” of the program. We make more functions pure, and push side effects to the outer layers. In practicality, we have to follow the direction of the FP bible: Since these functions are so common, how would we write an Android app without them? We can identify these side effects by looking for functions with return type Unit, where “ Unit” means “no meaningful return since it only performs side effects”. No side effects is a lofty goal when we consider pushing Fragments onto the backstack is a side effect, as is saving to shared preferences, as is updating content in a RecyclerView. Pure functions are functions with no side effects. In FP, we aim for an application constructed with pure functions. Let’s try and unpack some of the functional programming (FP) goodness in this article. There’s a sample Android project by Jorge Castillo, but it can be a bit intimidating. That being said, it’s not an easy framework to learn.
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