title: How to cast a let variable in swift
body: <p>I have created let variable with identifier varA, Then assigned a integer value to the same.</p>
  
  <pre><code>import cocoa
  var varA = 42
  </code></pre>
  
  <p>After these line i would like to have this varA to be <strong>store an float value</strong>. </p>
  
  <blockquote>
    <p>Just like in python i have used this feature</p>
  </blockquote>
  
  <p>Im getting<br>
  <code>error: cannot assign to 'let' value 'varA'</code></p>
  
  <p>How can i do this?
  Im using swift 3.0</p>