I think changing
gen String.to_atom("#{g}_z"), a, do: {:ok, v, a} # undefined function v/0
to
gen String.to_atom("#{g}_z"), a, do: {:ok, unquote(v), a} # should work fine this way
should work. As far as I can tell, you want to use a value of v that’s only available at compile time in the module, but as you have it, v and a are just regular variables declared in the body of a function.
