How to create a function pointer with predetermined arguments as double (*)(const double)

I am trying to use a method from a library that requires a function pointer as an input (of the type double (*)(const double)). The problem is that the function needs to have access to a few more values.

double f(vector<double> a) {
   return lib_func(std::bind(g, a, _1));
}

double g(vector<double> a, double x) {
    return a[0] + x;
}

What I need is a function double h(double x) { return a[0] + x; }, but I have been unable to create it of the type that the library function requires. (I have tried bind, lambda functions, creating a class or struct so that the function has access to the parameters, etc.).

I am relatively new to C++, so I am not sure what the type double (*)(const double) is.