Binding error in attempt to create lambda function

I have functions of the form:

num_t foo1(num_t a, num_t b, num_t c);
num_t foo2(num_t a, num_t b, num_t c);
...

and I want to create functions of the form

void bar1(struct value *p);
void bar2(struct value *p);
...

via some kind of transformation function ff3a(). bar1(), bar2() will be put in a lookup table.

My effort so far is:

using ff3_sig = std::function<num_t(num_t, num_t, num_t)>;
void ff3(ff3_sig &f, struct value* p)
{
        num_t a = p->Float, b = (p+1)->Float, c = (p+2)->Float;
        num_t res = f(a, b, c);
        p->Float = res;

}


std::function<void(struct value* p)>
ff3a(ff3_sig &f)
{
        auto g = [&](struct value* p) { ff3(f, p); };
        return g;
}

However, when I call ff3a(foo1) I get the error message:

 error: cannot bind non-const lvalue reference of type 
‘ff3_sig& {aka std::function<<unnamed-float:64>(<unnamed-float:64>, 
<unnamed-float:64>, <unnamed-float:64>)>&}’ to an rvalue of type 
‘ff3_sig {aka std::function<<unnamed-float:64>(<unnamed-float:64>, 
<unnamed-float:64>, <unnamed-float:64>)>}’