title: What does $0.1, $0.0, etc. mean in Swift?
body: <p>I saw a dictionary data, its value is like:</p>
  
  <pre><code>var myDict = ["name": "John",
                "age": 28]
  </code></pre>
  
  <p>I see a code like below:</p>
  
  <pre><code>myDict.flatMap {
             let a = $0.0
             let b = $0.1
             ...
   }
  </code></pre>
  
  <p>What does <code>$0.0</code> mean? What does <code>$0.1</code> mean? What is the difference between <code>$0</code> and <code>$0.1</code>?</p>