title: STL way to add a constant value to a std::vector
body: <p>Is there an algorithm in the standard library that can add a value to each element of a std::vector? 
  Something like</p>
  
  <pre><code>std::vector&lt;double&gt; myvec(5,0.);
  std::add_constant(myvec.begin(), myvec.end(), 1.);
  </code></pre>
  
  <p>that adds the value 1.0 to each element?</p>
  
  <p>If there isn't a nice (e.g. short, beautiful, easy to read) way to do this in STL, how about boost?</p>