title: What is a raw string?
body: <p>I came across this code snippet in C++17 draft n4713:</p>
  
  <pre><code>#define R "x"
  const char* s = R"y"; // ill-formed raw string, not "x" "y"
  </code></pre>
  
  <p>What is a "raw string"? What does it do?</p>