Why are the return values of these doubles -1.#IND?

Question

I have :

double score = cvMatchContourTrees( CT1, CT2, CV_CONTOUR_TREES_MATCH_I1, 0.0 );
        cout<

There are v

Answer 1

In my experience -1.#IND comes from imaginary numbers. So, doing cout << sqrt(-1.); should output -1.#IND