Deferable

Deferable is a concept in computer programming that refers to a task or operation whose execution can be postponed until a later point in time. This postponement can be for various reasons, such as optimizing performance, managing resources, or handling dependencies.

In some programming languages, like Go, the `defer` keyword is used to explicitly mark a function call as deferable. When a function with a deferred call is executed, the deferred call is not run immediately but is instead scheduled to run just before the surrounding function returns. This is particularly useful for cleanup operations, such as closing files or releasing locks, ensuring they are executed even if errors occur within the function.

The defer mechanism typically involves pushing the deferred function call onto a stack. As the surrounding function unwinds, the deferred calls are popped from the stack and executed in LIFO (Last-In, First-Out) order. This ensures that operations that were deferred last are executed first, which is often the desired behavior for nested resource management.

Beyond explicit `defer` keywords, the concept of deferrability is also present in other contexts. For example, in asynchronous programming, tasks might be deferred to a thread pool or event loop for later execution. Similarly, in systems with limited resources, certain non-critical operations might be deferred to periods of lower system load. The core idea remains the same: delaying an action until a more opportune moment.