title: Find a special part in a string
body: <p>I try to locate a special part in a string.
  The example of string as follow:
  <code>22.21594087,1.688530832,0</code></p>
  
  <p>I want to locate <code>1.688530832</code> out.
  I tried</p>
  
  <p><code>temp.substr(temp.find(",")+1,temp.rfind(","));</code></p>
  
  <p>and got <code>1.688530832,0</code>.
  I replaced rfind() with find_last_of() but still got the same result.</p>
  
  <p><code>temp.substr(temp.find(",")+1,temp.find_last_of(","));</code></p>
  
  <p>I know this is a simple problem and there are other solutions.But I just want to know why the rfind did not work. 
  Thank you very much!</p>