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| <H1 CLASS="title">DualUseFilter</H1> |
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| <H2>Description</H2> |
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| A DualUseFilter is a Filter which can act as an <A HREF="input_filter.html">InputFilter</A> or as an <A HREF="output_filter.html">OutputFilter</A>, but not as both simultaneously. |
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| DualUseFilters help reduce the number of different Filter types required to implement a particlar filtering algorithm. For example, by implementing <A HREF="../classes/regex_filter.html"><CODE>basic_regex_filter</CODE></A> as a DualUseFilter, the Iostreams library avoids having to define separate templates <CODE>basic_regex_input_filter</CODE> and <CODE>basic_regex_output_filter</CODE>. |
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| <H2>Refinement of</H2> |
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| <P><A HREF="input_filter.html">InputFilter</A>, <A HREF="output_filter.html">OutputFilter</A>.</P> |
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| <H2>Associated Types</H2> |
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| <TR><TD>Character type</TD><TD>The type of the characters in the filtered sequences</TD></TR> |
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| <TD>Category</TD> |
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| A type convertible to <A HREF="../guide/traits.html#category_tags"><CODE>filter_tag</CODE></A> and to <A HREF="../guide/modes.html#mode_tags"><CODE>dual_use</CODE></A> |
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| <TD>Mode</TD> |
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| The unique <I>most-derived</I> <A HREF="../guide/modes.html#mode_tags">mode tag</A> to which Category is convertible |
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| <H2>Valid Expressions / Semantics</H2> |
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| Same as <A HREF="bidirectional_filter.html">BidirectionalFilter</A>. |
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| <H2>Exceptions</H2> |
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| Same as <A HREF="bidirectional_filter.html">BidirectionalFilter</A>. |
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| <H2>Models</H2> |
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| <UL> |
| <LI>The <A HREF="../guide/text_processing.html">Text Processing Filters</A>. |
| <LI>The compression and decompression filters, except for <A HREF="../classes/gzip.html#basic_gzip_decompressor"><CODE>basic_gzip_decompressor</CODE></A>. |
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| <P CLASS="copyright">Revised 02 Feb 2008</P> |
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| <P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P> |
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| Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>) |
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