title: Regular expression for double values using QRegExp
body: <p>I am writing a regular expression checker for QLineEdit and I am using QRegExp.</p>
  
  <p>I have already wrote a int value checker:</p>
  
  <pre><code>QRegExp *expression_ = new QRegExp("^(0|[1-9]{1,1}[0-9]{0,9});
  </code></pre>
  
  <p>But I have complications with double values, to be more specific, I cannot separate the case of this numbers. F.E 0.210 or 0.001.</p>
  
  <p>Please help me to implement this feature for double values. 
  Thanks in advance. </p>