I didn't find the SCM_UNBNDP() that you mention but since mailing the list I stumbled on SCM_UNDEFINED and tried if(opt==SCM_UNDEFINED) ... and that seems to work. So (unless I am doing something bad) I think I am back on course - thanks!
Richard On Tue, 2011-08-23 at 13:54 +0200, [email protected] wrote: > On Tue, Aug 23, 2011 at 12:36:44PM +0100, Richard Shann wrote: > > I have defined a function with one needed and one optional arg, using > > > > scm_c_define_gsubr (name, 2, 0, 0, callback); > > > > in my function I need to test if the second argument is present, it > > looks like I need > > > > scm_defined_p(sym, env) > > > > but, if so, how do I find the value of env for the top-level > > environment? > > Not shure I understand you here, Richard. Where would sym come from? > If your function looks like this: > > (richards-function required-param an-optional-param) > > thane your c function needs exactly two parameters: > > ricks_c_func(SCM req, SCM opt) { > > ... > > if (!SCM_UNBNDP (opt)) { > /* opt wasn't provided, so do something here */ > } > > ... > > } > > > Does that help? > > Cheers, Ralf Mattes > > > Richard Shann > > > > >
