Consider the signal() function from the C standard: extern void (*signal(int, void(*)(int)))(int); Perfectly obscurely obvious – it’s a function that takes two arguments, an integer and a pointer to a function that takes an integer as an argument and returns nothing, and it (signal()) returns a pointer to a function that takes an integer as … Read more
You need to build a parameter pack of numbers and unpack them template<int …> struct seq { }; template<int N, int …S> struct gens : gens<N-1, N-1, S…> { }; template<int …S> struct gens<0, S…> { typedef seq<S…> type; }; // … void delayed_dispatch() { callFunc(typename gens<sizeof…(Args)>::type()); } template<int …S> void callFunc(seq<S…>) { func(std::get<S>(params) …); … Read more
A lambda can only be converted to a function pointer if it does not capture, from the draft C++11 standard section 5.1.2 [expr.prim.lambda] says (emphasis mine): The closure type for a lambda-expression with no lambda-capture has a public non-virtual non-explicit const conversion function to pointer to function having the same parameter and return types as … Read more
Anonymous inner class Say you want to have a function passed in with a String param that returns an int. First you have to define an interface with the function as its only member, if you can’t reuse an existing one. interface StringFunction { int func(String param); } A method that takes the pointer would … Read more
Note: Most of the answers cover function pointers which is one possibility to achieve “callback” logic in C++, but as of today not the most favourable one I think. What are callbacks(?) and why to use them(!) A callback is a callable (see further down) accepted by a class or function, used to customize the … Read more
Function pointers in C Let’s start with a basic function which we will be pointing to: int addInt(int n, int m) { return n+m; } First thing, let’s define a pointer to a function which receives 2 ints and returns an int: int (*functionPtr)(int,int); Now we can safely point to our function: functionPtr = &addInt; … Read more