title: Why have comparison operators been removed from standard library containers in C++ 20?
body: <p>I was browsing <a href="https://en.cppreference.com/w/cpp/container/vector/operator_cmp" rel="noreferrer">cppreference</a> and saw that <code>vector</code>'s comparison operations have been removed in C++20, and the spaceship operator (<code>&lt;=&gt;</code>) has been introduced. The same thing can be seen for many other standard library containers like <a href="https://en.cppreference.com/w/cpp/container/set/operator_cmp" rel="noreferrer"><code>set</code></a> and <a href="https://en.cppreference.com/w/cpp/container/map/operator_cmp" rel="noreferrer"><code>map</code></a>.</p>
  
  <p>How do I do the comparisons in the new standard? Also, will C++20 start giving errors on older code?</p>