Using emplace_back on an std::vector of a tuple

Suppose I have a struct, used later in a vector. I want to added an element to the vector using emplace_back without creating temporaries. I expected I would be able to use std::forward_as_tuple to pass two values as parameters for Foo. However, it fails to compile.
What’s the right way to do this?

#include <utility>
#include <vector>

struct Foo {
    int a;
    float b;    
    Foo(int a, float b) : a(a), b(b) {}
};

std::vector<tuple<int, int, Foo>> vec;
vec.emplace_back(0, 1, std::forward_as_tuple(1, 2.0f));

Of course, I could do this:

vec.emplace_back(0, 1, Foo(1, 2.0f));

But this creates a temporary Foo which defeats the purpose of using emplace_back in the first place.

>Solution :

A way that you can do this is to add a tuple constructor to Foo.

struct Foo {
    int a;
    float b;    
    Foo(int a, float b) : a(a), b(b) {}
    Foo(std::tuple<int, float> tup) : a(get<0>(tup)), b(get<1>(tup)) {}
};

If you were using std::pair, you could use the std::piecewise_construct_t constructor, however there isn’t a variadic version of that.

std::vector<std::pair<int, Foo>> vec;
vec.emplace_back(std::piecewise_construct, std::tuple(1), std::forward_as_tuple(1, 2.0f));