1 <!DOCTYPE HTML PUBLIC
"-//W3C//DTD HTML 4.01 Transitional//EN">
4 <TITLE>DualUseFilter
</TITLE>
5 <LINK REL=
"stylesheet" HREF=
"../../../../boost.css">
6 <LINK REL=
"stylesheet" HREF=
"../theme/iostreams.css">
12 <H1 CLASS=
"title">DualUseFilter
</H1>
20 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.
23 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>.
26 <H2>Refinement of
</H2>
28 <P><A HREF=
"input_filter.html">InputFilter
</A>,
<A HREF=
"output_filter.html">OutputFilter
</A>.
</P>
30 <H2>Associated Types
</H2>
32 <TABLE CELLPADDING=
"5" BORDER=
"1">
33 <TR><TD>Character type
</TD><TD>The type of the characters in the filtered sequences
</TD></TR>
37 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>
43 The unique
<I>most-derived
</I> <A HREF=
"../guide/modes.html#mode_tags">mode tag
</A> to which Category is convertible
48 <H2>Valid Expressions / Semantics
</H2>
50 Same as
<A HREF=
"bidirectional_filter.html">BidirectionalFilter
</A>.
54 Same as
<A HREF=
"bidirectional_filter.html">BidirectionalFilter
</A>.
59 <LI>The
<A HREF=
"../guide/text_processing.html">Text Processing Filters
</A>.
60 <LI>The compression and decompression filters, except for
<A HREF=
"../classes/gzip.html#basic_gzip_decompressor"><CODE>basic_gzip_decompressor
</CODE></A>.
67 <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>
69 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>)