In modern C++ development we can use multi-thread operations and parallel programming features in our applications in different ways of modern programming features. The std::thread class is a special class defined in <thread> header in the concurrency support library that comes with C++11. We can use the std::thread class in multi-thread operations with functor objects, and in this post, we explain how to use std::thread with a functor object in C++.
First, let’s learn what is functor and how we can use it.
What is functor in C++?
A functor is an object that can be used as a function or function pointer, this term is not same as function term in programming. We can pass many arguments with them; thus, we don’t need to define many global variables, we can use these kinds of variables in the scope that we use. We can create operators as given simple functor example below,
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class Ty { public: void operator()(int r) { double a = M_PI*r*r; } }; |
What is std::thread in C++?
In modern C++, a concurrency support library is designed to solve problems in multi-thread operations. This library includes built-in support for threads (std::thread), atomic operations (std::atomic), mutual exclusion (std::mutex), condition variables (std::condition_variable), and many other features.
The std::thread class is a special class defined in <thread> header that comes with C++11, and it allows multiple functions to execute and represents a single thread of execution concurrently. We can use the join() method of the thread that waits for the thread to finish its execution.
Let’s see how we can use std::thread with a functor object in C++.
Is there an example about running functor object with std::thread in C++?
Here is a std::thread example with a functor object ().
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#include <thread> class Ty { public: void operator()(int r) { double a = M_PI*r*r; } }; int main() { Ty o2; std::thread myt(o2, 5); // add myf(5) to thread myt.join(); // join thread to run in threads } |
Note that, we can use lambda expressions with std::thread which is a modern way of C++ programming.
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