why is SurfFeatureDetector class (in Features2d) missing from the open-ios libary?

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Title says it all really..any help much appreciated.

I included the appropriate library 'opencv2/features2d/features2d.hpp' but when I compile SURF isnt recognised.

Im trying to do this http://achuwilson.wordpress.com/2011/08/05/object-detection-using-surf-in-opencv-part-1/

If anyone has other examples please forward on

thx