std::function<R(Args...)>::assign

std::function<R(Args...)>::assign - cppreference.com

From cppreference.com

`template< class F, class Alloc > void assign( F&& f, const Alloc& alloc );`		(since C++11) (removed in C++17)

Initializes the target with f. The alloc is used to allocate memory for any internal data structures that the function might use.

Equivalent to function(std::allocator_arg, alloc, std::forward<F>(f)).swap(*this);.

f	-	callable function to initialize the target with
alloc	-	allocator to use to allocate memory for the internal data structures

(none)

May throw implementation-defined exceptions.