title: Declaring a Hash as a Constant with a default value in Ruby in one line
body: <p>My goal is to use a Hash with a default value as a class constant. To do this it seems to me that I must initialise a Hash in one line as a constant with pre-defined value and a default value.</p>
  
  <p>According to the Ruby documentation, I can set a default value in two way :</p>
  
  <ul>
  <li><p>In the constructor then by adding value as follow :</p>
  
  <pre><code>MY_HASH = Hash.new(-1)
  MY_HASH[1] = 0
  MY_HASH[2] = 42
  </code></pre></li>
  <li><p>By adding values first then setting the default value later :</p>
  
  <pre><code>MY_HASH = {
      1=&gt;0,
      2=&gt;42,
  }
  MY_HASH.default = -1
  </code></pre></li>
  </ul>
  
  <p>I tried to do it in one line like this, but it does not work :</p>
  
  <pre><code>    MY_HASH = {
          1=&gt;0,
          2=&gt;42,
      }.default = -1
  
     #It's the same as :
     MY_HASH = -1
  </code></pre>
  
  <p>Is there a way to declare a Hash with a default value in one line ?</p>