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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<title>Boost.Regex: Algorithm regex_replace</title>
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<h3><A href="../../../index.htm"><IMG height="86" alt="C++ Boost" src="../../../boost.png" width="277" border="0"></A></h3>
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<H1 align="center">Boost.Regex</H1>
<H2 align="center">Algorithm regex_replace</H2>
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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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<H3>Contents</H3>
<dl class="index">
<dt><A href="#synopsis">Synopsis</A> <dt><a href="#description">Description</a> <dt><A href="#examples">
Examples</A></dt></dl>
<H3><A name="synopsis"></A>Synopsis</H3>
<PRE>#include <<A href="../../../boost/regex.hpp">boost/regex.hpp</A>> </PRE>
<P>The algorithm regex_replace searches through a string finding
all the matches to the regular expression: for each match it then calls <A href="match_results.html#format">
match_results::format</A> to format the string and sends the result to the
output iterator. Sections of text that do not match are copied to the output
unchanged only if the <EM>flags</EM> parameter does not have the flag <A href="match_flag_type.html">
format_no_copy</A> set. If the flag <A href="match_flag_type.html">format_first_only</A>
is set then only the first occurrence is replaced rather than all
occurrences. <PRE>template <class OutputIterator, class BidirectionalIterator, class traits,
class Allocator, class charT>
OutputIterator <A href="#f1">regex_replace</A>(OutputIterator out,
BidirectionalIterator first,
BidirectionalIterator last,
const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
const basic_string<charT>& fmt,
<A href="match_flag_type.html">match_flag_type flags = match_default</A>);
template <class traits, class Allocator, class charT>
basic_string<charT> <A href="#f2">regex_replace</A>(const basic_string<charT>& s,
const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
const basic_string<charT>& fmt,
<A href="match_flag_type.html">match_flag_type flags = match_default</A>);
</PRE>
<H3><A name="description"></A>Description</H3>
<PRE><A name=f1></A>template <class OutputIterator, class BidirectionalIterator, class traits,
class Allocator, class charT>
OutputIterator regex_replace(OutputIterator out,
BidirectionalIterator first,
BidirectionalIterator last,
const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
const basic_string<charT>& fmt,
<A href="match_flag_type.html">match_flag_type flags = match_default</A>);</PRE>
<P>Enumerates all the occurences of expression <EM>e</EM> in the sequence [first,
last), replacing each occurence with the string that results by merging the
match found with the format string <EM>fmt</EM>, and copies the resulting
string to <EM>out</EM>. </P>
<P>If the flag format_no_copy is set in <EM>flags</EM> then unmatched sections of
text are not copied to output.
</P>
<P>If the flag format_first_only is set in <EM>flags</EM> then only the first
occurence of <EM>e</EM> is replaced.
</P>
<P>The manner in which the format string <EM>fmt</EM> is interpretted, along with
the rules used for finding matches, are determined by the <A href="match_flag_type.html">
flags</A> set in <EM>flags</EM></P>
<P><B>Effects:</B> Constructs an
<SPAN class="spelle">regex_iterator</SPAN>
object:
</P>
<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>
<P>and uses
<SPAN class="spelle">
<I>i</I></SPAN>
to enumerate through all of the matches <I>m</I> of type
<SPAN class="spelle">
<SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">match_results</SPAN>
</SPAN><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'"><<SPAN class="spelle">BidirectionalIterator</SPAN>> </SPAN>that
occur within the sequence [first, last).
</P>
<P>If no such matches are found
<SPAN class="grame">and </SPAN></P>
<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>
<P>then calls
</P>
<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>
<P>Otherwise, for each match found,
<SPAN class="grame">if </SPAN></P>
<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>
<P>calls
</P>
<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>
<P>and then calls
</P>
<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>
<P>Finally
<SPAN class="grame">if </SPAN></P>
<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>
<P>calls
</P>
<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>
<P><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'"></SPAN>where
<SPAN class="spelle">
<SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">last_m</SPAN>
</SPAN>
is a copy of the last match found.
</P>
<P>If
<SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">flags &
<SPAN class="spelle">format_first_only</SPAN></SPAN>
is non-zero then only the first match found is replaced.</P>
<P><STRONG>Throws:</STRONG> <CODE>std::runtime_error</CODE> if the complexity of
matching the expression against an N character string begins to exceed O(N<SUP>2</SUP>),
or if the program runs out of stack space while matching the expression (if
Boost.regex is <A href="configuration.html">configured</A> in recursive mode),
or if the matcher exhausts it's permitted memory allocation (if Boost.regex is <A href="configuration.html">
configured</A> in non-recursive mode).</P>
<P><B> Returns:</B> <CODE>out</CODE>.
</P>
<PRE><A name=f2></A>template <class traits, class Allocator, class charT>
basic_string<charT> regex_replace(const basic_string<charT>& s,
const <A href="basic_regex.html">basic_regex</A><charT, traits, Allocator>& e,
const basic_string<charT>& fmt,
<A href="match_flag_type.html">match_flag_type flags = match_default</A>);</PRE>
<P><B> Effects:</B> Constructs an object <CODE>basic_string<charT> result</CODE>,
calls <CODE>regex_replace(back_inserter(result), s.begin(), s.end(), e, fmt,
flags)</CODE>, and then returns <CODE>result</CODE>.
<H3><A name="examples"></A>Examples</H3>
<P>The following <A href="../example/snippets/regex_replace_example.cpp">example</A>
takes C/C++ source code as input, and outputs syntax highlighted HTML code.</P>
<P></P>
<PRE><FONT color=#008080>#include <fstream>
#include <sstream>
#include <string>
#include <iterator>
#include <boost/regex.hpp>
#include <fstream>
#include <iostream>
</FONT>
<FONT color=#000080><I>// purpose:
// takes the contents of a file and transform to
// syntax highlighted code in html format
</I></FONT>
boost::regex e1, e2;
<B>extern</B> <B>const</B> <B>char</B>* expression_text;
<B>extern</B> <B>const</B> <B>char</B>* format_string;
<B>extern</B> <B>const</B> <B>char</B>* pre_expression;
<B>extern</B> <B>const</B> <B>char</B>* pre_format;
<B>extern</B> <B>const</B> <B>char</B>* header_text;
<B>extern</B> <B>const</B> <B>char</B>* footer_text;
<B>void</B> load_file(std::string& s, std::istream& is)
{
s.erase();
s.reserve(is.rdbuf()->in_avail());
<B>char</B> c;
<B>while</B>(is.get(c))
{
<B>if</B>(s.capacity() == s.size())
s.reserve(s.capacity() * <FONT color=#000080>3</FONT>);
s.append(<FONT color=#000080>1</FONT>, c);
}
}
<B>int</B> main(<B>int</B> argc, <B>const</B> <B>char</B>** argv)
{
try{
e1.assign(expression_text);
e2.assign(pre_expression);
<B>for</B>(<B>int</B> i = <FONT color=#000080>1</FONT>; i < argc; ++i)
{
std::cout << <FONT color=#0000ff>"Processing file "</FONT> << argv[i] << std::endl;
std::ifstream fs(argv[i]);
std::string in;
load_file(in, fs);
std::string out_name(std::string(argv[i]) + std::string(<FONT color=#0000ff>".htm"</FONT>));
std::ofstream os(out_name.c_str());
os << header_text;
<FONT color=#000080><I>// strip '<' and '>' first by outputting to a
</I></FONT> <FONT color=#000080><I>// temporary string stream
</I></FONT> std::ostringstream t(std::ios::out | std::ios::binary);
std::ostream_iterator<<B>char</B>, <B>char</B>> oi(t);
boost::regex_replace(oi, in.begin(), in.end(),
e2, pre_format, boost::match_default | boost::format_all);
<FONT color=#000080><I>// then output to final output stream
</I></FONT> <FONT color=#000080><I>// adding syntax highlighting:
</I></FONT> std::string s(t.str());
std::ostream_iterator<<B>char</B>, <B>char</B>> out(os);
boost::regex_replace(out, s.begin(), s.end(),
e1, format_string, boost::match_default | boost::format_all);
os << footer_text;
}
}
<STRONG>catch</STRONG>(...)
{ <STRONG>return</STRONG> -1; }
<B>return</B> <FONT color=#000080>0</FONT>;
}
<B>extern</B> <B>const</B> <B>char</B>* pre_expression = <FONT color=#0000ff>"(<)|(>)|\\r"</FONT>;
<B>extern</B> <B>const</B> <B>char</B>* pre_format = <FONT color=#0000ff>"(?1<)(?2>)"</FONT>;
<B>const</B> <B>char</B>* expression_text = <FONT color=#000080><I>// preprocessor directives: index 1
</I></FONT> <FONT color=#0000ff>"(^[[:blank:]]*#(?:[^\\\\\\n]|\\\\[^\\n[:punct:][:word:]]*[\\n[:punct:][:word:]])*)|"
</FONT> <FONT color=#000080><I>// comment: index 2
</I></FONT> <FONT color=#0000ff>"(//[^\\n]*|/\\*.*?\\*/)|"
</FONT> <FONT color=#000080><I>// literals: index 3
</I></FONT> <FONT color=#0000ff>"\\<([+-]?(?:(?:0x[[:xdigit:]]+)|(?:(?:[[:digit:]]*\\.)?[[:digit:]]+(?:[eE][+-]?[[:digit:]]+)?))u?(?:(?:int(?:8|16|32|64))|L)?)\\>|"
</FONT> <FONT color=#000080><I>// string literals: index 4
</I></FONT> <FONT color=#0000ff>"('(?:[^\\\\']|\\\\.)*'|\"(?:[^\\\\\"]|\\\\.)*\")|"
</FONT> <FONT color=#000080><I>// keywords: index 5
</I></FONT> <FONT color=#0000ff>"\\<(__asm|__cdecl|__declspec|__export|__far16|__fastcall|__fortran|__import"
</FONT> <FONT color=#0000ff>"|__pascal|__rtti|__stdcall|_asm|_cdecl|__except|_export|_far16|_fastcall"
</FONT> <FONT color=#0000ff>"|__finally|_fortran|_import|_pascal|_stdcall|__thread|__try|asm|auto|bool"
</FONT> <FONT color=#0000ff>"|break|case|catch|cdecl|char|class|const|const_cast|continue|default|delete"
</FONT> <FONT color=#0000ff>"|do|double|dynamic_cast|else|enum|explicit|extern|false|float|for|friend|goto"
</FONT> <FONT color=#0000ff>"|if|inline|int|long|mutable|namespace|new|operator|pascal|private|protected"
</FONT> <FONT color=#0000ff>"|public|register|reinterpret_cast|return|short|signed|sizeof|static|static_cast"
</FONT> <FONT color=#0000ff>"|struct|switch|template|this|throw|true|try|typedef|typeid|typename|union|unsigned"
</FONT> <FONT color=#0000ff>"|using|virtual|void|volatile|wchar_t|while)\\>"
</FONT> ;
<B>const</B> <B>char</B>* format_string = <FONT color=#0000ff>"(?1<font color=\"#008040\">$&</font>)"
</FONT> <FONT color=#0000ff>"(?2<I><font color=\"#000080\">$&</font></I>)"
</FONT> <FONT color=#0000ff>"(?3<font color=\"#0000A0\">$&</font>)"
</FONT> <FONT color=#0000ff>"(?4<font color=\"#0000FF\">$&</font>)"
</FONT> <FONT color=#0000ff>"(?5<B>$&</B>)"</FONT>;
<B>const</B> <B>char</B>* header_text = <FONT color=#0000ff>"<HTML>\n<HEAD>\n"
</FONT> <FONT color=#0000ff>"<TITLE>Auto-generated html formated source</TITLE>\n"
</FONT> <FONT color=#0000ff>"<META HTTP-EQUIV=\"Content-Type\" CONTENT=\"text/html; charset=windows-1252\">\n"
</FONT> <FONT color=#0000ff>"</HEAD>\n"
</FONT> <FONT color=#0000ff>"<BODY LINK=\"#0000ff\" VLINK=\"#800080\" BGCOLOR=\"#ffffff\">\n"
</FONT> <FONT color=#0000ff>"<P> </P>\n<PRE>"</FONT>;
<B>const</B> <B>char</B>* footer_text = <FONT color=#0000ff>"</PRE>\n</BODY>\n\n"</FONT>;
</PRE>
<HR>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
24 Oct 2003
<!--webbot bot="Timestamp" endspan i-checksum="39359" --></p>
<p><i> Copyright John Maddock 1998-
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%Y" startspan -->
2003<!--webbot bot="Timestamp" endspan i-checksum="39359" --></i></p>
<P><I>Use, modification and distribution are subject to the Boost Software License,
Version 1.0. (See accompanying file <A href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</A>
or copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)</I></P>
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