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Introduction to std::packaged_task

Introduction to std::packaged_task

This lesson gives an introduction to std::packaged_task which is used in C++ for multithreading.

std::packaged_task pack is a wrapper for a callable in order for it to be invoked asynchronously. By calling pack.get_future() you get the associated future. Invoking the call operator on pack (pack()) executes the std::packaged_task and, therefore, executes the callable.

Dealing with std::packaged_task usually consists of four steps:

I. Wrap your work:

    std::packaged_task<int(int, int)> sumTask([](int a, int b){ return a + b; });

II. Create a future:

    std::future<int> sumResult= sumTask.get_future();

III. Perform the calculation:

    sumTask(2000, 11);

IV. Query the result:

    sumResult.get();

Here is an example showing the four ...