[Developers] fourth function overloads?

[dave fournier]

On 12/16/2014 08:08 AM, John Sibert wrote:

Probably because that is as far as I got that day and then something 
else happened.

> Does anyone know why the code for
> df1b2variable fourth(const df1b2variable& _z);
> is commented out in  df1b2-separable/df1b2fun.cpp
>
> or why there is not prototype for
> prevariable& fourth(const prevariable& v1)
> in fvar.hpp althouth the functions is implemented in linad99/fvar_op8.cpp
>