title: What part of Hindley-Milner do you not understand?
body: <p>I <em>swear</em> there used to be a <strong>T-shirt</strong> for sale featuring the immortal words:</p>
  
  <hr>
  
  <p>What part of</p>
  
  <p><img src="https://i.stack.imgur.com/xkKgE.png" alt="Hindley-Milner"></p>
  
  <p>do you <em>not</em> understand?</p>
  
  <hr>
  
  <p>In my case, the answer would be... all of it!</p>
  
  <p>In particular, I often see notation like this in Haskell papers, but I have no clue what any of it means. I have no idea what branch of mathematics it's supposed to be.</p>
  
  <p>I recognize the letters of the Greek alphabet of course and symbols such as "∉" (which usually means that something is not an element of a set).</p>
  
  <p>On the other hand, I've never seen "⊢" before (<a href="https://en.wikipedia.org/wiki/List_of_mathematical_symbols" rel="noreferrer">Wikipedia claims it might mean "partition"</a>). I'm also unfamiliar with the use of the vinculum here. (Usually, it denotes a fraction, but that does not <em>appear</em> to be the case here.)</p>
  
  <p>If somebody could at least tell me where to start looking to comprehend what this sea of symbols means, that would be helpful.</p>