title: what is the capacity of an empty vector?
body: <p>Looks like a stupid question. But comment to my <a href="https://stackoverflow.com/questions/1787856/what-is-the-element-value-in-an-uninitialized-vector/1787863#1787863">answer</a> to one of the SO question made me to think again.</p>
  
  <p>[ comment says, capacity need not be zero for empty vector]</p>
  
  <p>By default my answer would be 0 as there are no elements inside vector. It makes sense to keep the capacity as 0 and  on the first allocation it can be increased without any performance hits.</p>
  
  <p>But standard does not say anything one this.  ( I checked in Josuttis book as well). </p>
  
  <p>Is it purely implementation specific? Does any STL vendor use some arbitrary number as capcity for the empty vector?  </p>
  
  <p>Any thoughts...</p>