Function interp_is_active_binding 

fn interp_is_active_binding(
    positional: &[RValue],
    _named: &[(String, RValue)],
    _context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Check whether a binding is an active binding.

@param sym name of the binding (character string) @param env environment in which to check @return logical scalar