Kotlin is a functional programming language that provides support for key functional programming concepts. Some of the important functional programming features in Kotlin include lambda expressions, higher-order functions, lazy evaluations, and extension functions. Compared to Haskell and Scala, Kotlin has a less pure functional programming approach, but still shares many similar features.
Haskell is a purely functional programming language which means that it does not allow any side effects. It is a statically-typed language that is known for its strong type system and its ability to perform type inference at compile-time. Haskell heavily relies on immutability, recursion, and higher-order functions for building complex programs. It also uses a lazy evaluation strategy which means that values are only computed when they are actually needed.
Scala, on the other hand, is a hybrid functional and object-oriented programming language. It supports both imperative and functional programming paradigms and aims to be a more pragmatic language that can be used for various purposes. Scala allows for mutable data structures and side effects, but also provides various tools for building functional abstractions and expressing programs in a functional style. It supports higher-order functions, type inference, immutability by default, and lazy evaluation.
Kotlin falls somewhere in between Haskell and Scala. It allows for both functional and imperative programming styles, but puts more emphasis on the functional side. Kotlin supports mutable data structures and side effects, but encourages immutability and the use of immutable data structures. It also provides extension functions and function literals with receiver, which are powerful tools for building domain-specific languages and expressive APIs.
Overall, Kotlin’s design choices provide a good balance between functional and imperative programming styles. This can make Kotlin more approachable for developers who are transitioning from object-oriented languages like Java, while still providing a strong set of functional programming features. However, some developers may prefer the more strict functional programming approach of Haskell, while others may prefer the more pragmatic and flexible approach of Scala.