Comparing Actions with C++ Functions

As mentioned above, HPX actions are very similar to 'normal' C++ functions except that actions can be invoked remotely. The following table compares the way C++ functions can be invoked with the syntax used to apply an HPX action. This table assumes that func is an arbitrary C++ function or function object and act is an instance of an HPX action. R stands for an arbitrary result type.

Table 15. Comparing C++ Functions and HPX Actions

Invocation	C++ Function	HPX Action
Apply (fire & forget)	`hpx::apply(func, ...);`	`hpx::apply(act, id, ...);`
Asynchronous	std::future<R> f = std::async(func, ...); R r = f.get(); hpx::future<R> f = hpx::async(func, ...); R r = f.get();	hpx::future<R> f = hpx::async(act, id, ...); R r = f.get();
Synchronous	`R r = f(...)`	`R r = act(id, ...)`