are used throughout.  So, in the j0
example above, <code>(double j0 (double))</code> says we want access to j0, it returns
a C double, and it takes one argument, also a C double.  s7 tries to figure out
what the corresponding s7 type is, but in tricky cases, you should tell it
by replacing the bare type name with a list: <code>(C-type underlying-C-type)</code>.  For example,
the Snd function set_graph_style takes an (enum) argument of type graph_style_t.
This is actually an int, so we use <code>(graph_style