cv::log issue ?

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Hello, I have issues with the cv::log function. The documentations says that the cv::log function takes the natural logarithm of each element when the element value is not null and a constant C set to -700 otherwise. However, when I apply cv::log to a 3X1 null array (that is v = [0;0;0]), cv::log(v,answer); returns answer = [-1.#INF, -1.#INF, -1.#INF]. Shouldn't it return answer = [C, C, C] instead ? Thanks if someone can clarify !