title: Why is std::equal_to useful?
body: <p>The C++ standard library provides <a href="http://en.cppreference.com/w/cpp/utility/functional/equal_to"><code>std::equal_to</code></a>. This function object invokes <code>operator==</code> on type <code>T</code> by default. </p>
  
  <p>What's the benefit of using <code>std::equal_to</code>? Could you provide an example where <code>std::equal_to</code> is useful?</p>