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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<html>
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<head>
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<title>Boost.Regex: Algorithm regex_replace</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<LINK href="../../../boost.css" type="text/css" rel="stylesheet"></head>
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<body>
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<P>
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<TABLE id="Table1" cellSpacing="1" cellPadding="1" width="100%" border="0">
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<TR>
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<td vAlign="top" width="300">
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<h3><A href="../../../index.htm"><IMG height="86" alt="C++ Boost" src="../../../c++boost.gif" width="277" border="0"></A></h3>
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</td>
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<TD width="353">
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<H1 align="center">Boost.Regex</H1>
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<H2 align="center">Algorithm regex_replace</H2>
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</TD>
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<td width="50">
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<h3><A href="index.html"><IMG height="45" alt="Boost.Regex Index" src="uarrow.gif" width="43" border="0"></A></h3>
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</td>
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</TR>
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</TABLE>
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</P>
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<HR>
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<H3>Contents</H3>
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<dl class="index">
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<dt><A href="#synopsis">Synopsis</A> <dt><a href="#description">Description</a> <dt><A href="#examples">
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Examples</A></dt></dl>
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<H3><A name="synopsis"></A>Synopsis</H3>
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<PRE>#include <<A href="../../../boost/regex.hpp">boost/regex.hpp</A>> </PRE>
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<P>The algorithm regex_replace searches through a string finding
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all the matches to the regular expression: for each match it then calls <A href="match_results.html#format">
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match_results::format</A> to format the string and sends the result to the
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output iterator. Sections of text that do not match are copied to the output
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unchanged only if the <EM>flags</EM> parameter does not have the flag <A href="match_flag_type.html">
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format_no_copy</A> set. If the flag <A href="match_flag_type.html">format_first_only</A>
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is set then only the first occurrence is replaced rather than all
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occurrences. <PRE>template <class OutputIterator, class BidirectionalIterator, class traits,
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class Allocator, class charT>
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OutputIterator <A href="#f1">regex_replace</A>(OutputIterator out,
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BidirectionalIterator first,
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BidirectionalIterator last,
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const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
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const basic_string<charT>& fmt,
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<A href="match_flag_type.html">match_flag_type flags = match_default</A>);
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template <class traits, class Allocator, class charT>
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basic_string<charT> <A href="#f2">regex_replace</A>(const basic_string<charT>& s,
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const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
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const basic_string<charT>& fmt,
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<A href="match_flag_type.html">match_flag_type flags = match_default</A>);
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</PRE>
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<H3><A name="description"></A>Description</H3>
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<PRE><A name=f1></A>template <class OutputIterator, class BidirectionalIterator, class traits,
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class Allocator, class charT>
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OutputIterator regex_replace(OutputIterator out,
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BidirectionalIterator first,
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BidirectionalIterator last,
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const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
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const basic_string<charT>& fmt,
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<A href="match_flag_type.html">match_flag_type flags = match_default</A>);</PRE>
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<P>Enumerates all the occurences of expression <EM>e</EM> in the sequence [first,
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last), replacing each occurence with the string that results by merging the
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match found with the format string <EM>fmt</EM>, and copies the resulting
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string to <EM>out</EM>. </P>
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<P>If the flag format_no_copy is set in <EM>flags</EM> then unmatched sections of
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text are not copied to output.
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</P>
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<P>If the flag format_first_only is set in <EM>flags</EM> then only the first
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occurence of <EM>e</EM> is replaced.
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</P>
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<P>The manner in which the format string <EM>fmt</EM> is interpretted, along with
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the rules used for finding matches, are determined by the <A href="match_flag_type.html">
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flags</A> set in <EM>flags</EM></P>
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<P><B>Effects:</B> Constructs an
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<SPAN class="spelle">regex_iterator</SPAN>
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object:
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</P>
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<PRE><SPAN style="FONT-SIZE: 10pt">regex_iterator<</SPAN><SPAN class=spelle><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">BidirectionalIterator</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt">, </SPAN><SPAN class=spelle><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">charT</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt">, traits, Allocator> <BR> </SPAN><SPAN class=grame><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">i(</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt">first, last, e, flags)</SPAN>, </PRE>
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<P>and uses
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<SPAN class="spelle">
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<I>i</I></SPAN>
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to enumerate through all of the matches <I>m</I> of type
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<SPAN class="spelle">
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<SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">match_results</SPAN>
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</SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'"><<SPAN class="spelle">BidirectionalIterator</SPAN>> </SPAN>that
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occur within the sequence [first, last).
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</P>
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<P>If no such matches are found
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<SPAN class="grame">and </SPAN></P>
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<PRE><SPAN class=grame></SPAN><SPAN class=grame><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">!</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">(flags & <SPAN class=spelle>format_no_copy</SPAN>)</SPAN> </PRE>
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<P>then calls
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</P>
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<PRE><SPAN class=spelle><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">std::copy</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">(first, last, out)</SPAN>. </PRE>
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<P>Otherwise, for each match found,
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<SPAN class="grame">if </SPAN></P>
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<PRE><SPAN class=grame></SPAN><SPAN class=grame><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">!</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">(flags & <SPAN class=spelle>format_no_copy</SPAN>)</SPAN> </PRE>
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<P>calls
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</P>
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<PRE><SPAN class=spelle><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">std::copy</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">(<SPAN class=spelle>m.prefix</SPAN>().first, <SPAN class=spelle>m.prefix</SPAN>().last, out)</SPAN>, </PRE>
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<P>and then calls
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</P>
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<PRE><SPAN class=spelle><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">m.format</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">(out, <SPAN class=spelle>fmt</SPAN>, flags)</SPAN>. </PRE>
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<P>Finally
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<SPAN class="grame">if </SPAN></P>
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<PRE><SPAN class=grame></SPAN><SPAN class=grame><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">!</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">(flags & <SPAN class=spelle>format_no_copy</SPAN>)</SPAN> </PRE>
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<P>calls
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</P>
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<PRE><SPAN class=spelle><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">std::copy</SPAN></SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">(<SPAN class=spelle>last_m.suffix</SPAN>().first, <SPAN class=spelle>last_m,suffix</SPAN>().last, out) </SPAN></PRE>
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<P><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'"></SPAN>where
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<SPAN class="spelle">
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<SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">last_m</SPAN>
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</SPAN>
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is a copy of the last match found.
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</P>
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<P>If
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<SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">flags &
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<SPAN class="spelle">format_first_only</SPAN></SPAN>
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is non-zero then only the first match found is replaced.</P>
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<P><STRONG>Throws:</STRONG> <CODE>std::runtime_error</CODE> if the complexity of
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matching the expression against an N character string begins to exceed O(N<SUP>2</SUP>),
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or if the program runs out of stack space while matching the expression (if
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Boost.regex is <A href="configuration.html">configured</A> in recursive mode),
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or if the matcher exhausts it's permitted memory allocation (if Boost.regex is <A href="configuration.html">
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configured</A> in non-recursive mode).</P>
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<P><B> Returns:</B> <CODE>out</CODE>.
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</P>
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<PRE><A name=f2></A>template <class traits, class Allocator, class charT>
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basic_string<charT> regex_replace(const basic_string<charT>& s,
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const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
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const basic_string<charT>& fmt,
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<A href="match_flag_type.html">match_flag_type flags = match_default</A>);</PRE>
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<P><B> Effects:</B> Constructs an object <CODE>basic_string<charT> result</CODE>,
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calls <CODE>regex_replace(back_inserter(result), s.begin(), s.end(), e, fmt,
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flags)</CODE>, and then returns <CODE>result</CODE>.
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<H3><A name="examples"></A>Examples</H3>
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<P>The following <A href="../example/snippets/regex_replace_example.cpp">example</A>
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takes C/C++ source code as input, and outputs syntax highlighted HTML code.</P>
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<P></P>
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<PRE><FONT color=#008080>#include <fstream>
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#include <sstream>
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#include <string>
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#include <iterator>
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#include <boost/regex.hpp>
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#include <fstream>
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#include <iostream>
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</FONT>
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<FONT color=#000080><I>// purpose:
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// takes the contents of a file and transform to
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// syntax highlighted code in html format
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</I></FONT>
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boost::regex e1, e2;
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<B>extern</B> <B>const</B> <B>char</B>* expression_text;
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<B>extern</B> <B>const</B> <B>char</B>* format_string;
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<B>extern</B> <B>const</B> <B>char</B>* pre_expression;
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<B>extern</B> <B>const</B> <B>char</B>* pre_format;
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<B>extern</B> <B>const</B> <B>char</B>* header_text;
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<B>extern</B> <B>const</B> <B>char</B>* footer_text;
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<B>void</B> load_file(std::string& s, std::istream& is)
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{
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s.erase();
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s.reserve(is.rdbuf()->in_avail());
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<B>char</B> c;
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<B>while</B>(is.get(c))
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{
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<B>if</B>(s.capacity() == s.size())
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s.reserve(s.capacity() * <FONT color=#000080>3</FONT>);
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s.append(<FONT color=#000080>1</FONT>, c);
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}
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}
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<B>int</B> main(<B>int</B> argc, <B>const</B> <B>char</B>** argv)
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{
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try{
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e1.assign(expression_text);
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e2.assign(pre_expression);
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<B>for</B>(<B>int</B> i = <FONT color=#000080>1</FONT>; i < argc; ++i)
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{
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std::cout << <FONT color=#0000ff>"Processing file "</FONT> << argv[i] << std::endl;
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std::ifstream fs(argv[i]);
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std::string in;
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load_file(in, fs);
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std::string out_name(std::string(argv[i]) + std::string(<FONT color=#0000ff>".htm"</FONT>));
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std::ofstream os(out_name.c_str());
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os << header_text;
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<FONT color=#000080><I>// strip '<' and '>' first by outputting to a
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</I></FONT> <FONT color=#000080><I>// temporary string stream
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</I></FONT> std::ostringstream t(std::ios::out | std::ios::binary);
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std::ostream_iterator<<B>char</B>, <B>char</B>> oi(t);
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boost::regex_replace(oi, in.begin(), in.end(),
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e2, pre_format, boost::match_default | boost::format_all);
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<FONT color=#000080><I>// then output to final output stream
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</I></FONT> <FONT color=#000080><I>// adding syntax highlighting:
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</I></FONT> std::string s(t.str());
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std::ostream_iterator<<B>char</B>, <B>char</B>> out(os);
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boost::regex_replace(out, s.begin(), s.end(),
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e1, format_string, boost::match_default | boost::format_all);
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os << footer_text;
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}
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}
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<STRONG>catch</STRONG>(...)
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{ <STRONG>return</STRONG> -1; }
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<B>return</B> <FONT color=#000080>0</FONT>;
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}
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<B>extern</B> <B>const</B> <B>char</B>* pre_expression = <FONT color=#0000ff>"(<)|(>)|\\r"</FONT>;
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<B>extern</B> <B>const</B> <B>char</B>* pre_format = <FONT color=#0000ff>"(?1<)(?2>)"</FONT>;
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<B>const</B> <B>char</B>* expression_text = <FONT color=#000080><I>// preprocessor directives: index 1
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</I></FONT> <FONT color=#0000ff>"(^[[:blank:]]*#(?:[^\\\\\\n]|\\\\[^\\n[:punct:][:word:]]*[\\n[:punct:][:word:]])*)|"
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</FONT> <FONT color=#000080><I>// comment: index 2
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</I></FONT> <FONT color=#0000ff>"(//[^\\n]*|/\\*.*?\\*/)|"
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</FONT> <FONT color=#000080><I>// literals: index 3
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</I></FONT> <FONT color=#0000ff>"\\<([+-]?(?:(?:0x[[:xdigit:]]+)|(?:(?:[[:digit:]]*\\.)?[[:digit:]]+(?:[eE][+-]?[[:digit:]]+)?))u?(?:(?:int(?:8|16|32|64))|L)?)\\>|"
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</FONT> <FONT color=#000080><I>// string literals: index 4
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</I></FONT> <FONT color=#0000ff>"('(?:[^\\\\']|\\\\.)*'|\"(?:[^\\\\\"]|\\\\.)*\")|"
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</FONT> <FONT color=#000080><I>// keywords: index 5
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</I></FONT> <FONT color=#0000ff>"\\<(__asm|__cdecl|__declspec|__export|__far16|__fastcall|__fortran|__import"
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</FONT> <FONT color=#0000ff>"|__pascal|__rtti|__stdcall|_asm|_cdecl|__except|_export|_far16|_fastcall"
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</FONT> <FONT color=#0000ff>"|__finally|_fortran|_import|_pascal|_stdcall|__thread|__try|asm|auto|bool"
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</FONT> <FONT color=#0000ff>"|break|case|catch|cdecl|char|class|const|const_cast|continue|default|delete"
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</FONT> <FONT color=#0000ff>"|do|double|dynamic_cast|else|enum|explicit|extern|false|float|for|friend|goto"
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</FONT> <FONT color=#0000ff>"|if|inline|int|long|mutable|namespace|new|operator|pascal|private|protected"
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</FONT> <FONT color=#0000ff>"|public|register|reinterpret_cast|return|short|signed|sizeof|static|static_cast"
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</FONT> <FONT color=#0000ff>"|struct|switch|template|this|throw|true|try|typedef|typeid|typename|union|unsigned"
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</FONT> <FONT color=#0000ff>"|using|virtual|void|volatile|wchar_t|while)\\>"
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</FONT> ;
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<B>const</B> <B>char</B>* format_string = <FONT color=#0000ff>"(?1<font color=\"#008040\">$&</font>)"
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</FONT> <FONT color=#0000ff>"(?2<I><font color=\"#000080\">$&</font></I>)"
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</FONT> <FONT color=#0000ff>"(?3<font color=\"#0000A0\">$&</font>)"
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</FONT> <FONT color=#0000ff>"(?4<font color=\"#0000FF\">$&</font>)"
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</FONT> <FONT color=#0000ff>"(?5<B>$&</B>)"</FONT>;
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<B>const</B> <B>char</B>* header_text = <FONT color=#0000ff>"<HTML>\n<HEAD>\n"
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</FONT> <FONT color=#0000ff>"<TITLE>Auto-generated html formated source</TITLE>\n"
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</FONT> <FONT color=#0000ff>"<META HTTP-EQUIV=\"Content-Type\" CONTENT=\"text/html; charset=windows-1252\">\n"
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</FONT> <FONT color=#0000ff>"</HEAD>\n"
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</FONT> <FONT color=#0000ff>"<BODY LINK=\"#0000ff\" VLINK=\"#800080\" BGCOLOR=\"#ffffff\">\n"
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</FONT> <FONT color=#0000ff>"<P> </P>\n<PRE>"</FONT>;
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<B>const</B> <B>char</B>* footer_text = <FONT color=#0000ff>"</PRE>\n</BODY>\n\n"</FONT>;
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</PRE>
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<HR>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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17 May 2003
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<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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</p>
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<P><I><EFBFBD> Copyright <a href="mailto:jm@regex.fsnet.co.uk">John Maddock</a> 1998-<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%Y" startspan --> 2003<!--webbot bot="Timestamp" endspan i-checksum="39359" --></I></P>
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<P align="left"><I>Permission to use, copy, modify, distribute and sell this software
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and its documentation for any purpose is hereby granted without fee, provided
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that the above copyright notice appear in all copies and that both that
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copyright notice and this permission notice appear in supporting documentation.
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Dr John Maddock makes no representations about the suitability of this software
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for any purpose. It is provided "as is" without express or implied warranty.</I></P>
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</body>
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</html>
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