Is there a pure virtual function in the C++ Standard Library?
<p>In <a href="https://isocpp.org/blog/2016/01/functional-programming-in-cpp-nicola-gigante-meetingcpp-2015" rel="nofollow noreferrer">Nicola Gigante's lecture in 2015</a>, he mentions (at the beginning) that there are no pure virtual functions in the Standard Library (or he's not aware of any). I believe that Alex Stepanov was against this language feature but since the initial STL design, have any pure virtuals creeped into the Standard library?</p>

<p>FWIW (and correct me if I'm wrong) the deleters in unique pointers ultimately use virtual dispatching in most implementations but these are not pure virtuals.</p>