Im refferring to this OpenCV function on this post IplImage* cvLoadImage(const char* filename, int iscolor=CV_LOAD_IMAGE_COLOR ) I'm tring to get the c functionality where i can access the imageData struct member of IplImage with the below statement (more info here http://docs.opencv.org/modules/core/doc/old_basic_structures.html?highlight=...) IplImage* converted_image= cvLoadImage("c:\\box_in_scene.png",0):converted_image->imageData when i try with this (dp converted-image (Load-image "/home/w/Documents/opencv- 2.4.6.1/samples/c/box_in_scene.png" 0)) (cffi:with-foreign-slots ((image-data) converted-image (:struct ipl-image)) (cffi:foreign-string-to-lisp image-data)) I get the post title error message. I also get message when i try to setf IMAGE-DATA to another variable or list it .....i get same thing with foreign-slot-value here is sampling of the more than 6 pages of converted_image->imageData that was cout'ed in C P1']}stqouqwruM/./22330/00+1)/+%+8S~sx{zzx|x~|x~y{~Y(&&''()+,%(%$%! $l~