Problem Statement
Explain function types in Kotlin and how to use them as parameters and return values.
Explanation
Function types in Kotlin are declared using parentheses for parameters and arrow for return type like open paren Int comma Int close paren arrow Int for a function taking two Ints and returning Int, and you can store functions in variables, pass them as parameters, or return them from functions. You can make function types nullable with question mark, provide parameter names for clarity like open paren x colon Int comma y colon Int close paren arrow Int, and use typealias to create readable names for complex function types.
Higher-order functions use function types as parameters enabling functional programming patterns, and you can invoke function type variables by calling them like regular functions. Extension function types like String dot open paren close paren arrow Int define functions that extend a type, useful for DSL creation and APIs that configure objects.
Function types are fundamental to Kotlin's functional programming support, enabling patterns like callbacks, strategies, decorators, and functional composition. Understanding function types helps you write more flexible and reusable code using functions as first-class values.
