> marpa_v_step() returns -2 on failure:
> http://jeffreykegler.github.io/Marpa-web-site/libmarpa_api/latest/Stepping-through-the-valuator.html
>
> An error code is set, which can be retrieved with these methods:
> http://jeffreykegler.github.io/Marpa-web-site/libmarpa_api/latest/Error-methods.htm
marpa_v_step() returns -2 on failure:
http://jeffreykegler.github.io/Marpa-web-site/libmarpa_api/latest/Stepping-through-the-valuator.html
An error code is set, which can be retrieved with these methods:
http://jeffreykegler.github.io/Marpa-web-site/libmarpa_api/latest/Error-methods.html#Error-met