title: c++ how to get "one digit exponent" with printf
body: <p>Is there a way to print in scientific notation less than 3 places for exponent part of number?
  The 6.1 formatting  doesn't affect exponent but only the number part:</p>
  
  <pre><code>var=1.23e-9;
  printf ("%e\n", var);
  printf ("%6.1e\n", var);
  </code></pre>
  
  <p>gives</p>
  
  <pre><code>1.230000e-009
  1.2e-009
  </code></pre>
  
  <p>I've also tried this in wxWidgets with formatting of string but the behavior is the same.</p>
  
  <pre><code>m_var-&gt;SetLabel(wxString::Format(wxT("%6.1e"),var));
  </code></pre>
  
  <p>What I'd like to have is <code>1.2e-9</code>.</p>