title: Why is Num not shown with an Eq and Show constriant
body: <p>In the Haskell report (p. 76 <a href="https://www.haskell.org/definition/haskell2010.pdf" rel="nofollow noreferrer">https://www.haskell.org/definition/haskell2010.pdf</a>) the type class hierarchy is shown as:</p>
  <p><a href="https://i.stack.imgur.com/2x3D9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2x3D9.png" alt="Type class hierarchy" /></a></p>
  <p>But when I look at the definition of Num I get:</p>
  <p><a href="https://i.stack.imgur.com/vw7XG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vw7XG.png" alt=":i Num in GHCI" /></a></p>
  <p>Why is Num not defined as <code>class Eq a, Show a =&gt; Num a where</code>?</p>