13.28 <iosfwd>

The <iosfwd> header provides forward declarations of the various I/O-related classes and templates. The forward declarations are incomplete type declarations. (Read about complete and incomplete types in Chapter 6.) By using <iosfwd> you can sometimes avoid including the complete definitions of the I/O classes, and thereby save some compilation time.

It is always safe to include <iosfwd> and any of the other I/O headers, even if they both declare the same type.

Because <iosfwd> does not provide any complete type declarations, this section contains only Table 13-18, which lists each type name with a reference to the header (if any) that is required for the complete type.

Table 13-18. Forward type declarations in <iosfwd>

Type declaration	Header
template<typename T> class allocator	<memory>
template<typename charT, typename traits=char_traits<charT> > class basic_filebuf	<fstream>
template<typename charT, typename traits=char_traits<charT> > class basic_fstream	<fstream>
template<typename charT, typename traits=char_traits<charT> > class basic_ifstream	<fstream>
template<typename charT, typename traits=char_traits<charT> > class basic_ios	<ios>
template<typename charT, typename traits=char_traits<charT> > class basic_iostream	<istream>
template<typename charT, typename traits=char_traits<charT> > class basic_istream	<istream>
template<typename charT, typename traits=char_traits<charT>, typename Alloc = allocator<charT> > class basic_istringstream	<sstream>
template<typename charT, typename traits=char_traits<charT> > class basic_ofstream	<fstream>
template<typename charT, typename traits=char_traits<charT> > class basic_ostream	<ostream>
template<typename charT, typename traits=char_traits<charT>, typename Alloc = allocator<charT> > class basic_ostringstream	<sstream>
template<typename charT, typename traits=char_traits<charT> > class basic_streambuf	<streambuf>
template<typename charT, typename traits=char_traits<charT>, typename Alloc = allocator<charT> > class basic_stringbuf	<sstream>
template<typename charT, typename traits=char_traits<charT>, typename Alloc = allocator<charT> > class basic_stringstream	<sstream>
template<typename charT> class char_traits	<string>
template<> class char_traits<char>	<string>
template<> class char_traits<wchar_t>	<string>
typedef basic_filebuf<char> filebuf	<fstream>
template <typename state> class fpos	<ios>
typedef basic_fstream<char> fstream	<fstream>
typedef basic_ifstream<char> ifstream	<fstream>
typedef basic_ios<char> ios	<ios>
typedef basic_iostream<char> iostream	<istream>
typedef basic_istream<char> istream	<istream>
template<typename charT, typename traits=char_traits<charT> > class istreambuf_iterator	<iterator>
typedef basic_istringstream<char> istringstream	<sstream>
typedef basic_ofstream<char> ofstream	<fstream>
typedef basic_ostream<char> ostream	<ostream>
template<typename charT, typename traits=char_traits<charT> > class ostreambuf_iterator	<iterator>
typedef basic_ostringstream<char> ostringstream	<sstream>
typedef basic_streambuf<char> streambuf	<streambuf>
typedef fpos<char_traits<char>::state_type> streampos	N/A
typedef basic_stringbuf<char> stringbuf	<sstream>
typedef basic_stringstream<char> stringstream	<sstream>
typedef basic_filebuf<wchar_t> wfilebuf	<fstream>
typedef basic_fstream<wchar_t> wfstream	<fstream>
typedef basic_ifstream<wchar_t> wifstream	<fstream>
typedef basic_ios<wchar_t> wios	<ios>
typedef basic_iostream<wchar_t> wiostream	<istream>
typedef basic_istream<wchar_t> wistream	<istream>
typedef basic_istringstream<wchar_t> wistringstream	<sstream>
typedef basic_ofstream<wchar_t> wofstream	<fstream>
typedef basic_ostream<wchar_t> wostream	<ostream>
typedef basic_ostringstream<wchar_t> wostringstream	<sstream>
typedef basic_streambuf<wchar_t> wstreambuf	<streambuf>
typedef fpos<char_traits<wchar_t>::state_type> wstreampos	N/A
typedef basic_stringbuf<wchar_t> wstringbuf	<sstream>
typedef basic_stringstream<wchar_t> wstringstream	<sstream>