title: I want to store "8+8" as the result of a num type calculation. (An error occurs when I try to convert "8+8" as a String to a num.)
body: <h3>Assumptions and what we want to achieve</h3>
  <p>I want to store 8+8 and so on as the result of a num type calculation.</p>
  <h3>Source code.</h3>
  <pre class="lang-dart prettyprint-override"><code> void culuclator() {
     
        display= display.replaceAll('÷', '/');
        display= display.replaceAll('x', '*');
        print(display);
        num result=num.parse(display);
       print(display);
  
      }
  
  </code></pre>
  <h3>My considerations and additional information</h3>
  <p>It would be great if you could answer my question assuming that display is originally a String type 8+8, etc.
  I thought that the result of 8+8 calculation can be stored as num, but &quot;+&quot; can't be converted as num.
  What is the best way to deal with this?
  Thank you very much for your help.</p>