about before function in typeinfo
<p>I am reading modern C++ design. Following is the text snippet taken from typeinfo description.</p>

<blockquote>
  <p>The before member function introduces
  an ordering relationship for type_info
  objects. Using type_info::before, you
  can perform indexing on type_info
  objects.</p>
  
  <p>If you want to sort type_info objects, again you must actually store
  pointers to type_info, and this time
  you must use the before member
  function. Consequently, if you want to
  use STL's ordered containers with
  type_info, you must write a little
  functor and deal with pointers.</p>
</blockquote>

<p>In above description, what is meant by indexing on type_info objects and how can we achieve this using "before" function.</p>

<p>Also another question is what does author mean if we want to use STL containers with type_info, we must write a little functor and deal with pointers.</p>

<p>Thanks!</p>
