27 Iterators library [iterators]

27.6 Stream iterators [stream.iterators]

27.6.3 Class template istreambuf_­iterator [istreambuf.iterator]

27.6.3.1 Class template istreambuf_­iterator​::​proxy [istreambuf.iterator.proxy]

namespace std {
  template<class charT, class traits = char_traits<charT>>
  class istreambuf_iterator<charT, traits>::proxy { // exposition only
    charT keep_;
    basic_streambuf<charT,traits>* sbuf_;
    proxy(charT c, basic_streambuf<charT,traits>* sbuf)
      : keep_(c), sbuf_(sbuf) { }
  public:
    charT operator*() { return keep_; }
  };
}
Class istreambuf_­iterator<charT,traits>​::​proxy is for exposition only.
An implementation is permitted to provide equivalent functionality without providing a class with this name.
Class istreambuf_­iterator<charT, traits>​::​proxy provides a temporary placeholder as the return value of the post-increment operator (operator++).
It keeps the character pointed to by the previous value of the iterator for some possible future access to get the character.