I'm trying to implement FAST feature detection/ description computation using OpenCV 3.1 in C++.

My code:

```
Ptr<cv::FastFeatureDetector> fast = cv::FastFeatureDetector::create();
fast->detectAndCompute(img1, Mat(), keypoints1, desc);

```

But when I apply detectAndCompute, I get an error. After debugging, I saw that in the source file (features2d.cpp) this must throw and error:

```
//[In source file features2d.cpp]
/* Detects keypoints and computes the descriptors */
     void Feature2D::detectAndCompute( InputArray, InputArray,
                                      std::vector<KeyPoint>&,
                                      OutputArray,
                                      bool )
    {
        CV_Error(Error::StsNotImplemented, "");
    }

```

Why is this not implemented? And is there another way for me to use FAST?