Have you used inline functions?

Yes, I have used them. Inline functions in Kotlin are used to improve performance, especially when working with high-order functions and lambdas. The compiler replaces the call to an inline function with its body at the call site, avoiding the overhead of a function call.

Examples of usage:

// Example of an inline function for executing a block of code
inline fun runTimed(block: () -> Unit) {
    val start = System.currentTimeMillis()
    block()
    val end = System.currentTimeMillis()
    println("Execution time: ${end - start} ms")
}

// Using the inline function
runTimed {
    // Your code to measure
    Thread.sleep(100)
}

// Example of an inline function with non-local return
inline fun findUser(userId: Int, users: List<User>): User? {
    for (user in users) {
        if (user.id == userId) {
            return user // non-local return
        }
    }
    return null
}

// Using the inline function
val user = findUser(123, listOfUsers)

It is important to remember the potential downsides of inline functions, such as possible increase in bytecode size and debugging complexity in some cases. Therefore, they should be used thoughtfully.