Kotlin Advanced Concepts - Programming

Structured concurrency ties every coroutine to a scope, so child coroutines cannot outlive their parent and cancellation propagates automatically. When a scope is canceled or fails, its children stop too, which prevents leaked coroutines and makes concurrent code easier to reason about.

A suspend function can pause its execution without blocking the underlying thread, resuming later when its awaited work completes. It can only be called from a coroutine or another suspend function, and the compiler transforms it into a state machine to enable this cooperative suspension.

Extension functions let you add methods to a type you do not own, such as adding a helper to String, without inheritance or wrapper classes. They are resolved statically and improve readability by letting you call the function with familiar dot syntax.

A sealed class restricts subclasses to the same file or module, so the compiler knows every possible subtype. This makes when expressions over them exhaustive without an else branch, unlike open classes, while allowing each subtype to hold different data, unlike simple enums.

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