Load calculations, and using software to do them, are key traits of the contractor of the future, according to a new ACCA report.
The code above might look ugly, but all you have to understand is that the FutureBuilder widget takes two arguments: future and builder, future is just the future you want to use, while builder is a function that takes two parameters and returns a widget. FutureBuilder will run this function before and after the future completes.
The function template std::async runs the function f asynchronously (potentially in a separate thread which might be a part of a thread pool) and returns a std::future that will eventually hold the result of that function call.
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The class template std::future provides a mechanism to access the result of asynchronous operations: An asynchronous operation (created via std::async, std::packaged_task, or std::promise) can provide a std::future object to the creator of that asynchronous operation. The creator of the asynchronous operation can then use a variety of methods to query, wait for, or extract a value from the std ...
An asynchronous operation (created via std::async, std::packaged_task, or std::promise) can provide a std::future object to the creator of that asynchronous operation. The creator of the asynchronous operation can then use a variety of methods to query, wait for, or extract a value from the std::future.
These actions will not block for the shared state to become ready, except that they may block if all following conditions are satisfied: The shared state was created by a call to std::async. The shared state is not yet ready. The current object was the last reference to the shared state. (since C++14)
C++ includes built-in support for threads, atomic operations, mutual exclusion, condition variables, and futures.
The class template std::packaged_task wraps any Callable target (function, lambda expression, bind expression, or another function object) so that it can be invoked asynchronously. Its return value or exception thrown is stored in a shared state which can be accessed through std::future objects.
If the future is the result of a call to std::async that used lazy evaluation, this function returns immediately without waiting. This function may block for longer than timeout_duration due to scheduling or resource contention delays. The standard recommends that a steady clock is used to measure the duration.