title: Swift dictionary comprehension
body: <p>Other languages such as Python let you use a dictionary comprehension to make a dict from an array, but I haven't figure out how to do this in Swift. I thought I could use something like this but it doesn't compile:</p>
  
  <pre><code>let x = ["a","b","c"]
  let y = x.map( { ($0:"x") })
  // expected y to be ["a":"x", "b":"x", "c":"x"]
  </code></pre>
  
  <p>What is the correct way to generate a dictionary from an array in swift?</p>