title: Converting QString to float gives me errors
body: <p>I'm trying to convert a string to float  and vice versa but the compiler complains about it. In the editor I get <code>implicit conversion increases floating-point precision: 'float' to 'double'</code>. but I'm not converting a float to double at least not as far as I know.</p>
  <pre class="lang-none prettyprint-override"><code>C:\Qt\5.13.0\mingw73_64\include\QtCore\qstring.h:649: error: 'double QString::toFloat(bool*) const' cannot be overloaded
       double toFloat(bool *ok=nullptr) const;
              ^~~~~~~
  </code></pre>
  <p>And right below it:</p>
  <pre class="lang-none prettyprint-override"><code>C:\Qt\5.13.0\mingw73_64\include\QtCore\qstring.h:648: error: with 'float QString::toFloat(bool*) const'
       float toFloat(bool *ok=nullptr) const;
             ^~~~~~~
  </code></pre>
  <p>is what i get but I don't know why. The only thing I can imagine right now is that c++ can't tell if which version of <code>toFloat</code> I'm trying to use. The compiler points me out in the QString class where I can see two versions of <code>toFloat</code> that are identical except for the return type. I seriously have no clue how to solve this so I'd like some guidance on what I should add here to get it resolved.</p>
  <pre><code>else if (btnId == &quot;=&quot;) {
   QRegExp separator(&quot;[(+|-|/|*)]&quot;);
      QStringList data = displayText.split(separator);
  
      bool ok = false;
      float result = 0.0;
  
      while (!data.isEmpty()) {
          QString str = data[0];
          data.pop_front();
  
          if (str == &quot;+&quot; || str == &quot;-&quot; || str == &quot;/&quot; || str == &quot;*&quot;)
          {
              QString str2 = data[0];
              data.pop_front();
  
              if (str == &quot;+&quot;) {
                  double tmpF = str2.toFloat(&amp;ok);
                  result += tmpF;
              }
              else if (str == &quot;-&quot;) {
                  double tmpF = str2.toFloat(&amp;ok);
                  result -= tmpF;
              }
              else if (str == &quot;/&quot;) {
                  double tmpF = str2.toFloat(&amp;ok);
                  result /= tmpF;
              }
              else if (str == &quot;*&quot;) {
                  double tmpF = str2.toFloat(&amp;ok);
                  result *= tmpF;
              }
          }
  
          displayText.setNum(result, 'g', 6);
      }
  }
  </code></pre>