title: Declaring a constant in swift
body: <p>As I read the <a href="https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/GuidedTour.html#//apple_ref/doc/uid/TP40014097-CH2-XID_1" rel="nofollow">swift guide</a> it says: <code>The value of a constant doesn’t need to be known at compile time, but you must assign it a value exactly once.</code></p>
  
  <p>I tried in REPL but without any luck:</p>
  
  <pre><code>let aConst;
  aConst=23;
  </code></pre>
  
  <p>So how to declare a constant without setting initial value?</p>