Programming Kotlin

Inlining Functions with Lambdas

Lambdas are elegant, and it’s convenient to pass functions to functions, but there’s a catch—performance. Kotlin provides the inline keyword to eliminate the call overhead in order to improve performance, to provide non-local control flow such as a return from within forEach(), and to pass reified type parameters as we saw in ​Reified Type Parameters​.

Before we delve into ways to improve performance of functions that use lambdas, let’s set some context. Every higher-order function we write doesn’t need the solutions we’ll see in this section. A good amount of code we write will enjoy a reasonable performance and need nothing special. But in some situations—such as when a higher-order function contains a loop ...