forked from boostorg/regex
151 lines
5.8 KiB
HTML
151 lines
5.8 KiB
HTML
<!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: Perl-Style Format String Syntax</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link rel="stylesheet" type="text/css" href="../../../boost.css">
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</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" width="277" alt="C++ Boost" src="../../../boost.png" 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">Perl-Style Format String Syntax</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" width="43" alt="Boost.Regex Index" src="uarrow.gif" 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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<P>Perl-style format strings treat all characters as literals except '$' and '\'
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which start placeholder and escape sequences respectively.</P>
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<P>Placeholder sequences specify that some part of what matched the regular
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expression should be sent to output as follows:</P>
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<P>
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<TABLE id="Table2" cellSpacing="4" cellPadding="1" width="100%" border="0">
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<TR>
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<TD><STRONG>Placeholder</STRONG></TD>
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<TD><STRONG>Meaning</STRONG></TD>
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</TR>
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<TR>
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<TD>$&</TD>
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<TD>Outputs what matched the whole expression.</TD>
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</TR>
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<TR>
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<TD>$`</TD>
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<TD>Outputs the text between the end of the last match found (or the start of the
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text if no previous match was found), and the start of the current match.</TD>
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</TR>
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<TR>
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<TD>$'</TD>
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<TD>Outputs all the text following the end of the current match.</TD>
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</TR>
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<TR>
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<TD>$$</TD>
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<TD>Outputs a literal '$'</TD>
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</TR>
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<TR>
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<TD>$n</TD>
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<TD>Outputs what matched the n'th sub-expression.</TD>
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</TR>
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</TABLE>
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</P>
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<P>Any $-placeholder sequence not listed above, results in '$' being treated as a
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literal.</P>
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<P>An escape character followed by any character <EM>x</EM>, outputs that
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character unless <EM>x</EM> is one of the escape sequences shown below.</P>
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<P>
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<TABLE id="Table3" cellSpacing="4" cellPadding="1" width="100%" border="0">
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<TR>
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<TD><STRONG>Escape</STRONG></TD>
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<TD><STRONG>Meaning</STRONG></TD>
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</TR>
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<TR>
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<TD>\a</TD>
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<TD>Outputs the bell character: '\a'.</TD>
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</TR>
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<TR>
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<TD>\e</TD>
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<TD>Outputs the ANSI escape character (code point 27).</TD>
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</TR>
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<TR>
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<TD>\f</TD>
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<TD>Outputs a form feed character: '\f'</TD>
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</TR>
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<TR>
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<TD>\n</TD>
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<TD>Outputs a newline character: '\n'.</TD>
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</TR>
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<TR>
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<TD>\r</TD>
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<TD>Outputs a carriage return character: '\r'.</TD>
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</TR>
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<TR>
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<TD>\t</TD>
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<TD>Outputs a tab character: '\t'.</TD>
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</TR>
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<TR>
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<TD>\v</TD>
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<TD>Outputs a vertical tab character: '\v'.</TD>
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</TR>
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<TR>
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<TD>\xDD</TD>
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<TD>Outputs the character whose hexadecimal code point is 0xDD</TD>
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</TR>
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<TR>
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<TD>\x{DDDD}</TD>
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<TD>Outputs the character whose hexadecimal code point is 0xDDDDD</TD>
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</TR>
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<TR>
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<TD>\cX</TD>
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<TD>Outputs the ANSI escape sequence "escape-X".</TD>
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</TR>
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<TR>
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<TD>\D</TD>
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<TD>If <EM>D</EM> is a decimal digit in the range 1-9, then outputs the text that
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matched sub-expression <EM>D</EM>.</TD>
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</TR>
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<TR>
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<TD>\l</TD>
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<TD>Causes the next character to be outputted, to be output in lower case.</TD>
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</TR>
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<TR>
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<TD>\u</TD>
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<TD>Causes the next character to be outputted, to be output in upper case.</TD>
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</TR>
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<TR>
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<TD>\L</TD>
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<TD>Causes all subsequent characters to be output in lower case, until a \E is
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found.</TD>
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</TR>
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<TR>
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<TD>\U</TD>
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<TD>Causes all subsequent characters to be output in upper case, until a \E is
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found.</TD>
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</TR>
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<TR>
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<TD>\E</TD>
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<TD>Terminates a \L or \U sequence.</TD>
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</TR>
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</TABLE>
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</P>
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<P>
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<HR>
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<P></P>
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<P></P>
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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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24 Nov 2004
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<!--webbot bot="Timestamp" endspan i-checksum="39359" --></p>
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<p><i><EFBFBD> Copyright John Maddock 2004</i></p>
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<P><I>Use, modification and distribution are subject to the Boost Software License,
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Version 1.0. (See accompanying file <A href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</A>
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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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</body>
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</html>
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