How can I point a function with function overload?

Question

#include <stdio.h>
#include <functional>

int foo(int x)
{
    return x;
}

int foo(int a, int b)
{
    return a + b;
}

int main()
{
    std::function<int(int)> guiFunc2 = foo;      //error : no suitable constructor exists to convert from "<unknown-type>" to "std::function<int(int)>"
    std::function<int(int, int)> guiFunc1 = foo; //error : no suitable constructor exists to convert from "<unknown-type>" to "std::function<int(int, int)>"

    return 0;
}

I want to make two function pointers to functions with same name but this code does not work.

It's easy to just change the functions name but I would like to know if it's possible to make funtion pointers with same name.

Thanks.

Hmm... why did @rafix07 remove the answer? It looked good, didn't it? — Ted Lyngmo
– Ted Lyngmo, Commented Mar 4, 2020 at 11:05
Please, note the difference between function overloading and overriding. Overriding is related to virtual functions and inheritance. — Daniel Langr
– Daniel Langr, Commented Mar 4, 2020 at 11:12
@DanielLangr Good catch. Edited since the code shows overloading. — Ted Lyngmo
– Ted Lyngmo, Commented Mar 4, 2020 at 11:14

VLL · Accepted Answer · 2020-03-04 11:05:55Z

4

Cast the address to correct type before assignment:

std::function<int(int)> guiFunc2 = static_cast<int(*)(int)>(foo);
std::function<int(int, int)> guiFunc1 = static_cast<int(*)(int, int)>(foo);

answered Mar 4, 2020 at 11:05

VLL

10.4k1 gold badge39 silver badges61 bronze badges

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

3 Comments

GamerCoder Over a year ago

May I ask one more thing? What I've learnt is that 'c++ compiler discriminates one overrided function from another by check its 'arguments' and 'function name'' and the functions in my code have different arguments. Why must I type-cast them?

VLL Over a year ago

@GamerCoder You are not calling the function, so there are no arguments from which to deduct the type.

Ted Lyngmo Over a year ago

@GamerCoder int(*guiFunc2)(int) = foo; int(*guiFunc1)(int,int) = foo; works though if you don't like the casting.

Marek R · Accepted Answer · 2020-03-04 11:15:01Z

0

For me this is more handy:

    auto a = [](int x) { return foo(x); };
    auto b = [](int a, int b) { return foo(a, b); };

https://wandbox.org/permlink/yjc5EiEY97wgfN9b

Result should be same as other answer.

answered Mar 4, 2020 at 11:15

Marek R

40.3k6 gold badges70 silver badges165 bronze badges

Collectives™ on Stack Overflow

How can I point a function with function overload?

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