A DualUseFilter is a Filter which can act as an InputFilter or as an OutputFilter, but not as both simultaneously.
    DualUseFilters help reduce the number of different Filter types required to implement a particlar filtering algorithm. For example, by implementing basic_regex_filter as a DualUseFilter, the Iostreams library avoids having to define separate templates basic_regex_input_filter and basic_regex_output_filter.
| Character type | The type of the characters in the filtered sequences | 
| Category | A type convertible to filter_tagand todual_use | 
| Mode | The unique most-derived mode tag to which Category is convertible | 
basic_gzip_decompressor.
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© Copyright 2004-2007 Jonathan Turkanis
Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)