title: What does the keyword 'implicit' mean when it's placed in front of lambda expression parameter?
body: <p>I have seen this kind of code many times before, most recently at scala-user mailing list:</p>
  
  <pre><code>context(GUI) { implicit ec =&gt;
    // some code
  }
  </code></pre>
  
  <p><code>context</code> is defined as: </p>
  
  <pre><code>def context[T](ec: ExecutionContext)(block: ExecutionContext =&gt; T): Unit = { 
    ec execute { 
      block(ec) 
    } 
  }
  </code></pre>
  
  <p>What purpose does the keeyword <code>implicit</code> achieve when placed in front of a lambda expression parameter?</p>