How to implement function(f)(x)(y, z)(g)(r) in C++?

Question

I have been trying to implement the following function:

MonsterFunction(f)(x)(y,z)(g)(r);

Where f is a function that accepts three parameters. x, y, z are the parameters which are passed to the function f and all of that is passed to the function g and the parameter r is also passed to the function g and the final result is returned.

I have successfully implemented MonsterFunction(f)(x)(y,z) , but I just can not figure out how to implement the above function.

Here is the code for what I have already accomplished:

std::function<std::function<int(int, int)>(int)> MonsterFunction(std::function<int(int, int, int)> f){
    return [f](int x1){
        return[f, x1](int y1, int z1){
            return f(x1, y1, z1);
        };
    };
}

Keep in mind that I only want to accomplish this with std::function and lambda-closure functions .

Answer 1

I've actually did it, after a little break I was able to implement it. It is easy as long as you track the nesting carefully. Here is my final code:

std::function<std::function<std::function<std::function<int(int)>(int(int, int))>(int, int)>(int)> MonsterFunction(std::function<int(int, int, int)> f){
    return [f](int x1){
        return[f, x1](int y1, int z1){
            int result = f(x1, y1, z1);
            return [result](int g(int, int)){
                return[result,g](int r){
                    return g(result, r);
                };
            };
        };
    };
}

Now I am able to do calls like this MonsterFunction(Sum)(5)(5,4)(Multiply)(4) .

Edit

As Quentin suggested, using auto as the return type makes the function more concise:

auto MonsterFunction(std::function<int(int, int, int)> f){
    return [f](int x1){
        return[f, x1](int y1, int z1){
            int result = f(x1, y1, z1);
            return [result](int g(int, int)){
                return[result,g](int r){
                    return g(result, r);
                };
            };
        };
    };
}