[Cffi-devel] What's the best way to convert c+ classes into Lisp

Joeish W joeish80829 at yahoo.com
Fri Apr 4 14:28:43 UTC 2014


I have a bunch or C wrappers for C++ OpenCV code I'm writing and I was hoping someone could show me how the best way would be in CFFI to write theses functions.  They're from a C++ class
the OpenCV Point_ class defined here http://docs.opencv.org/modules/core/doc/basic_structures.html?highlight=assignto#Point_


Here are the functions below. So far I'm making the top 2 functions point0 and point2 use the same name "point" with this function:

(defun point (&optional (x nil) (y nil)) 
       (cond ((eq (or x y) nil) 
          (point0)) 
         ((and x y) 
          (point2 x y)) 
         (t nil))) 
 
but I also have functions  to retrieve the x and y coordinates of a point that belong to the same class. I call those point-x and point-y..I was hoping someone could write me up the best way on how to use these Point_ class wrappers . Is it with defclass or define-foreign-type or am I already doing a good job? I could use this info in making all my other class wrappers correctly.


;; Point* cv_create_Point(int x, int y)  
(defcfun ("cv_create_Point" point0) (:pointer point) 
  "Point constructor") 
 
 
;; Point* cv_create_Point(int x, int y)  
(defcfun ("cv_create_Point2" point2) (:pointer point) 
  "Point constructor" 
  (x :int) 
  (y :int)) 
  
;; _Tp x, y 
;; int cv_Point_getX(Point* self)  
(defcfun ("cv_Point_getX" point-x) :int  
  "Retrieves X coordinate of a point" 
  (self (:pointer point))) 
 
 
;; _Tp x, y 
;; int cv_Point_getY(Point* self) 
(defcfun ("cv_Point_getY" point-y) :int  
  "Retrieves y coordinate of a point" 
  (self (:pointer point))) 
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