cppdraft_translate/cppdraft/iostream/forward/overview.md

[iostream.forward.overview]

31 Input/output library [input.output]

31.3 Forward declarations [iostream.forward]

31.3.2 Overview [iostream.forward.overview]

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The class template specializationbasic_ios<charT, traits> serves as a virtual base class for the class templatesbasic_istream,basic_ostream, and class templates derived from them.

basic_iostream is a class template derived from bothbasic_istream<charT, traits> andbasic_ostream<charT, traits>.

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The class template specializationbasic_streambuf<charT, traits> serves as a base class for class templatesbasic_stringbuf,basic_filebuf, andbasic_syncbuf.

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The class template specializationbasic_istream<charT, traits> serves as a base class for class templatesbasic_istringstream andbasic_ifstream.

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The class template specializationbasic_ostream<charT, traits> serves as a base class for class templatesbasic_ostringstream,basic_ofstream, andbasic_osyncstream.

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The class template specializationbasic_iostream<charT, traits> serves as a base class for class templatesbasic_stringstream andbasic_fstream.

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[Note 1:

For each of the class templates above, the program is ill-formed iftraits​::​char_type is not the same type ascharT ([char.traits]).

— end note]

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Other typedef-names define instances of class templates specialized forchar orwchar_t types.

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Specializations of the class templatefpos are used for specifying file position information.

[Example 1:

The typesstreampos andwstreampos are used for positioning streams specialized onchar andwchar_t respectively.

— end example]

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[Note 2:

This synopsis suggests a circularity betweenstreampos andchar_traits.

An implementation can avoid this circularity by substituting equivalent types.

— end note]