title: opencv matrix brace operator
body: <p>I've noticed in many examples/tutorials that people use the brace operator "()" for matrix access, which is confusing for me in some cases.</p>
  
  <p>The question is:
  Let's assume we have a n*m matrix (3x4, for example) named M. What elements will be returned by accessing it via "M(0)", or "M(1)", or any other singular parameter inside the braces? I thought that you are supposed to specify both the row and the column (like "M(0,1)" or something like that).</p>