c++: std::vector of std::function with arbitrary signatures

Question

Is it possible to create an std::vector that can hold an std::function with any signature? (The function arguments would all be pre-bound.)

Answer 1

Is it possible to create an std::vector that can hold an std::function with any signature? (The function arguments would all be pre-bound.)

So you're wondering if you can use a vector to hold objects of different types except that you've wrapped them all up in a single type?

Yes, you can store a bunch of items that all have the same type in a vector.

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Or maybe you're trying to ask "How do I wrap callable objects such that they'll have the type I need?"

bind can handle the special case where you only need to remove or reorder parameters in order to get something convertible to the common type. In order to handle the general case where you may need choose the return type, add parameters, etc., you simply have to write new functions. Lambda's can make it easy to do that inline:

std::vector<std::function<common_signature> F;

double foo(std::string);
// for a common signature of void()
F.push_back([]{ foo("hello"); });

int bar(void);
// for a common signature of int (int)
F.push_back( [](int i) { return bar() + i; });

int baz(void);
// for a common signature of std::complex<double> (void)
F.push_back( []() -> std::complex<double> { return {0,baz()}; });

Answer 2

This should work:

#include <iostream>
#include <functional>
#include <vector>

void hello() { std::cout << "Hello\n"; }
void hello2(const char * name) { std::cout << "Hello " << name << '\n'; }

int main()
{

    std::vector<std::function<void()>> v;
    v.push_back(hello);
    v.push_back(std::bind(hello2, "tim"));
    v[0]();
    v[1]();
}

How are you doing it?