title: Indexing vectors and arrays with +:
body: <p>I am seeing a code in SystemVerilog which has something like this:</p>
  
  <pre><code>if(address[2*pointer+:2])
    do_something;
  </code></pre>
  
  <p>How should I understand the <code>+:</code> when indexing this vector?</p>
  
  <p>I found that it is called bit slicing, but I can't find an explanation about it.</p>