Answer

An inline function instructs the compiler to copy the function's code and paste it directly into the call site, instead of creating a standard function call object.

Why use it?

• Performance: Reduces overhead of function calls and object allocation, especially for Higher-Order Functions (functions that take lambdas).
• Without `inline`, every lambda passed to a function creates an anonymous class object in Java bytecode, which costs memory.

Example

```kotlin inline fun executeOp(op: () -> Unit) { println("Start") op() println("End") }

// Usage executeOp { println("Working") } ```

Compiler output (conceptually): ```kotlin println("Start") println("Working") // The lambda body is pasted here println("End") ```

Caveat

Don't inline large functions, as it increases the bytecode size of your application.