Visual Lisp: how to call functions in external C++ DLL

Question

I have a C++ dll I have written (native, not .net), and I would like to use its functionality from Visual Lisp. Can anyone point me to an example of how to do this, or at l

Answer 1

I solved this by writing an activex/COM wrapper for my dll, which I think should make it easier to link to in future. Starting a thread on the swamp yielded some answers from nice people about how to call COM from Visual Lisp. For the record, it looks something like this:

//in c++... (header and IDL file also needed)
hresult timestwo(double in,double* out)
{
  *out = in*2;
  return S_OK;
}

;; in Lisp...
(vl-load-com)
(setq myinstance (vlax-create-object "mycomwrapperdll.mycomwrapperclass"))
(setq num 12.34)
(vlax-invoke-method myinstance 'timestwo num 'newnum)
(vlax-release-object myinstance)
;; newnum now contains 24.68