title: concatenating strings using "+" in c++
body: <p>I am a novice in C++ and i am referring Accelerated C++. While trying one of its exercise questions which says:</p>
  
  <pre><code>Are the following definitions valid? Why or why not?
  const std::string exclam = "!";
  const std::string message = "Hello" + ", world" + exclam;
  </code></pre>
  
  <p>When i tried &amp; executed the program i am getting an error as:</p>
  
  <blockquote>
    <p>invalid operands of types to binary operator +.</p>
  </blockquote>
  
  <p>But the following code works perfectly fine:</p>
  
  <pre><code>const std::string hello = "Hello";
  const std::string message = hello + ", world" + "!";
  </code></pre>
  
  <p>I am not clear with its execution! why this concatenation in the first case not working?</p>
  
  <p>Thanks!I am using DEV C++.</p>