Why is there no error with `randn` when I remove the` cv :: `

I accidentally forgot the namespace cv::

when I used randn

it and it compiled without error. This is my code

#include <iostream>
#include <opencv2/core/core.hpp>

int main( int argc, char** argv )
{
    std::cout << "\n%%( Random Generator )%%\n"; 
    cv::Mat G = cv::Mat::ones(4,4, CV_64FC1);
    cv::Mat m = cv::Mat::zeros(1,1, CV_64FC1);
    cv::Mat s = cv::Mat::ones(1,1, CV_64FC1);
    std::cout << G << std::endl;
    randn(G, m, s);
   std::cout << G << std::endl;

    return 0;
}

      

        
        
        
      

    

I am running the code on Windows

cl /EHsc main.cpp /Fetest.exe /I D:\xxxx\opencv_2.4.10\build\include /link /LIBPATH:D:\xxxx\opencv_2.4.10\build\x86\vc12\lib opencv_core2410.lib

      

        
        
        
      

    

My question is, is this function defined from a namespace cv

?