scm_defined_p(sym, env)

[Richard Shann]

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?

Richard Shann