Storing arguments and function and using them in another function

Question

Welcome, this is very rare use-case question.
So, here is what I'm trying to do - lets say I have a variadic template function which takes T ...args and a function type FuncT funcName, so here is what we have so far:

template<typename FuncT, typename ...T>
void myFunction(FuncT (*funcName), T ...args);

Now, I want to store my function at void (*)() (this store functions). This works just fine.

std::deque<void (*)()> functions;
func = functions.front();
func(std::forward<T>(args)...); //args is vardict template argument

Now, I can just pass a function to my function as in:

template<typename FuncT, typename T>

int sharedArgument;

void setArg(int x){
  sharedArgument = x;
}
template<typename FuncT>
void myFunction(FuncT funcName){
  funcName(sharedArgument);
}

void function(int i){
  std::cout << i;
}

int main(){
  setArg(5);
  myFunction(function);
}

Now, I know this is unnecesary, but i want to present a more complicated problem that im having trouble with.

When i want to store arguemnts, I will probably use std::tuple, its design to store arguments, but
Main question is:
How do i store variable amount of arguments in tuple and then perfectly forward them as normal arguments to some function, so that function receiving

function(std::tupleArgumentsHere...);

will read it as

function(5, 42, "yes", 3.14);

I will use this to store arguments and pass them to std::thread.

Thank you, Cheers.

soo std::bind?

KamilCuk
– KamilCuk

2021-02-01 17:27:09 +00:00
Commented Feb 1, 2021 at 17:27 — KamilCuk
– KamilCuk, Commented Feb 1, 2021 at 17:27

Yakk - Adam Nevraumont · Accepted Answer · 2021-02-01 17:05:13Z

1

Use std::apply. It is new in c++17. If you cannot, write your own.

In c++14, make an index sequence the same length as your tuple. Then func(std::get<Is>(std::forward<Tup>(tup))...).

In c++11 do the same thing but write your own index sequence.

answered Feb 1, 2021 at 17:05

Yakk - Adam Nevraumont

280k31 gold badges367 silver badges585 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

latekvo Over a year ago

Tuple is variable length, thats the problem

Yakk - Adam Nevraumont Over a year ago

@arma apply works with variable length tuples. So long as you know the function type and the tuple type, just call apply with the actual correctly typed values.

latekvo Over a year ago

Thanks, would be glad to know if there is c++11 way that works like apply, but still marking as the answear, thank you!

Potatoswatter · Accepted Answer · 2021-02-01 17:20:09Z

0

std::bind stores the function and the arguments together. It returns a callable object encapsulating a copy of the argument values.

You can also use its "placeholder" facility in case there are additional arguments to add after calling queue.front().

answered Feb 1, 2021 at 17:20

Potatoswatter

139k29 gold badges281 silver badges435 bronze badges

Collectives™ on Stack Overflow

Storing arguments and function and using them in another function

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related