title: STL container's read-only operations
body: <p>Need advice here: which of the STL container's operations are considered read-only? Take <code>vector&lt;int&gt;</code> as example, would it be safe to say that any operation that does not alter the underlying int data is read-only? I am writing a multi-threaded program, but not too sure if it is thread-safe to pass container by reference/pointer.</p>
  
  <p>Between, will the same rules apply to basic_string as well? Any recommended resource that helps for quickly gaining understanding on internal mechanism of STL container? Thanks.</p>