title: Need help figuring out data type of declaration in C++
body: <p>I am following this <a href="https://trungams.github.io/2020-08-23-a-simple-http-server-from-scratch/" rel="nofollow noreferrer">tutorial</a>.  The following declaration found in <a href="https://github.com/trungams/http-server/blob/master/src/main.cc" rel="nofollow noreferrer">main.cc</a> has me stumped:</p>
  <pre><code>auto say_hello = [](const HttpRequest&amp; request) -&gt; HttpResponse {...}
  </code></pre>
  <p><a href="https://i.stack.imgur.com/nx7kL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nx7kL.png" alt="img" /></a></p>
  <p>This is shown in the debugging window, but I don't quite get what it is.  What is the data type represented by this <code>auto</code> keyword?  What is the data type created by the square brackets after the equal sign?  I suppose <code>HttpResponse</code> is not the return type of <code>say_hello</code>?</p>
  <p>Thank you so much!!!</p>