ostreambuf_iterator&
operator=(charT c);
Requires: sbuf_ != nullptr.
Effects: If failed() yields false, calls sbuf_->sputc(c); otherwise has no effect.
Returns: *this.
ostreambuf_iterator& operator*();
Returns: *this.
ostreambuf_iterator& operator++();
ostreambuf_iterator& operator++(int);
Returns: *this.
Requires: sbuf_ != nullptr.
Returns: true if in any prior use of member operator=, the call to sbuf_->sputc() returned traits::eof(); or false otherwise.