title: Type Constraints in Data Declaration Haskell
body: <p>I'm using Haskell and trying to write the following:</p>
  
  <pre><code>data Scale s = Scale s s
  </code></pre>
  
  <p>However, I want to make it so that <code>s</code> must be something that of the Num type class, like Int or Double. Is that possible to do using Haskell and GHC?</p>