title: Why guards are called 'guards'?
body: <p>Does anyone know what is the origin of the name for the construct called <strong>guards</strong>?</p>
  
  <pre><code>func x
      | cond1 -&gt; expr1  
      ...
      | condN -&gt; exprN
  </code></pre>
  
  <p>Wikipedia article <a href="https://en.wikipedia.org/wiki/Guard_(computer_science)" rel="nofollow noreferrer"> Guard_(computer_science)</a> gives some historical perspective, but lacks explanation for where name came from (it just mentions that SASL was one of the first to use the name).</p>
  
  <p>So far I found references to Edsger Dijkstra and his Guarded Command Language. Was he first to use the term 'guard'?</p>