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- <title>Boost-Extended Format String Syntax</title>
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- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_regex.format.boost_format_syntax"></a><a class="link" href="boost_format_syntax.html" title="Boost-Extended Format String Syntax">Boost-Extended
- Format String Syntax</a>
- </h3></div></div></div>
- <p>
- Boost-Extended format strings treat all characters as literals except for
- '$', '\', '(', ')', '?', and ':'.
- </p>
- <h5>
- <a name="boost_regex.format.boost_format_syntax.h0"></a>
- <span class="phrase"><a name="boost_regex.format.boost_format_syntax.grouping"></a></span><a class="link" href="boost_format_syntax.html#boost_regex.format.boost_format_syntax.grouping">Grouping</a>
- </h5>
- <p>
- The characters '(' and ')' perform lexical grouping, so use \( and \) if
- you want a to output literal parenthesis.
- </p>
- <h5>
- <a name="boost_regex.format.boost_format_syntax.h1"></a>
- <span class="phrase"><a name="boost_regex.format.boost_format_syntax.conditionals"></a></span><a class="link" href="boost_format_syntax.html#boost_regex.format.boost_format_syntax.conditionals">Conditionals</a>
- </h5>
- <p>
- The character '?' begins a conditional expression, the general form is:
- </p>
- <p>
- ?Ntrue-expression:false-expression
- </p>
- <p>
- where N is decimal digit.
- </p>
- <p>
- If sub-expression N was matched, then true-expression is evaluated and sent
- to output, otherwise false-expression is evaluated and sent to output.
- </p>
- <p>
- You will normally need to surround a conditional-expression with parenthesis
- in order to prevent ambiguities.
- </p>
- <p>
- For example, the format string "(?1foo:bar)" will replace each
- match found with "foo" if the sub-expression $1 was matched, and
- with "bar" otherwise.
- </p>
- <p>
- For sub-expressions with an index greater than 9, or for access to named
- sub-expressions use:
- </p>
- <p>
- ?{INDEX}true-expression:false-expression
- </p>
- <p>
- or
- </p>
- <p>
- ?{NAME}true-expression:false-expression
- </p>
- <h5>
- <a name="boost_regex.format.boost_format_syntax.h2"></a>
- <span class="phrase"><a name="boost_regex.format.boost_format_syntax.placeholder_sequences"></a></span><a class="link" href="boost_format_syntax.html#boost_regex.format.boost_format_syntax.placeholder_sequences">Placeholder
- Sequences</a>
- </h5>
- <p>
- Placeholder sequences specify that some part of what matched the regular
- expression should be sent to output as follows:
- </p>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col>
- <col>
- </colgroup>
- <thead><tr>
- <th>
- <p>
- Placeholder
- </p>
- </th>
- <th>
- <p>
- Meaning
- </p>
- </th>
- </tr></thead>
- <tbody>
- <tr>
- <td>
- <p>
- $&
- </p>
- </td>
- <td>
- <p>
- Outputs what matched the whole expression.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $MATCH
- </p>
- </td>
- <td>
- <p>
- As $&
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- ${^MATCH}
- </p>
- </td>
- <td>
- <p>
- As $&
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $`
- </p>
- </td>
- <td>
- <p>
- Outputs the text between the end of the last match found (or the
- start of the text if no previous match was found), and the start
- of the current match.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $PREMATCH
- </p>
- </td>
- <td>
- <p>
- As $`
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- ${^PREMATCH}
- </p>
- </td>
- <td>
- <p>
- As $`
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $'
- </p>
- </td>
- <td>
- <p>
- Outputs all the text following the end of the current match.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $POSTMATCH
- </p>
- </td>
- <td>
- <p>
- As $'
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- ${^POSTMATCH}
- </p>
- </td>
- <td>
- <p>
- As $'
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $+
- </p>
- </td>
- <td>
- <p>
- Outputs what matched the last marked sub-expression in the regular
- expression.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $LAST_PAREN_MATCH
- </p>
- </td>
- <td>
- <p>
- As $+
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $LAST_SUBMATCH_RESULT
- </p>
- </td>
- <td>
- <p>
- Outputs what matched the last sub-expression to be actually matched.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $^N
- </p>
- </td>
- <td>
- <p>
- As $LAST_SUBMATCH_RESULT
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $$
- </p>
- </td>
- <td>
- <p>
- Outputs a literal '$'
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $n
- </p>
- </td>
- <td>
- <p>
- Outputs what matched the n'th sub-expression.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- ${n}
- </p>
- </td>
- <td>
- <p>
- Outputs what matched the n'th sub-expression.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- $+{NAME}
- </p>
- </td>
- <td>
- <p>
- Outputs whatever matched the sub-expression named "NAME".
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- <p>
- Any $-placeholder sequence not listed above, results in '$' being treated
- as a literal.
- </p>
- <h5>
- <a name="boost_regex.format.boost_format_syntax.h3"></a>
- <span class="phrase"><a name="boost_regex.format.boost_format_syntax.escape_sequences"></a></span><a class="link" href="boost_format_syntax.html#boost_regex.format.boost_format_syntax.escape_sequences">Escape
- Sequences</a>
- </h5>
- <p>
- An escape character followed by any character x, outputs that character unless
- x is one of the escape sequences shown below.
- </p>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col>
- <col>
- </colgroup>
- <thead><tr>
- <th>
- <p>
- Escape
- </p>
- </th>
- <th>
- <p>
- Meaning
- </p>
- </th>
- </tr></thead>
- <tbody>
- <tr>
- <td>
- <p>
- \a
- </p>
- </td>
- <td>
- <p>
- Outputs the bell character: '\a'.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \e
- </p>
- </td>
- <td>
- <p>
- Outputs the ANSI escape character (code point 27).
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \f
- </p>
- </td>
- <td>
- <p>
- Outputs a form feed character: '\f'
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \n
- </p>
- </td>
- <td>
- <p>
- Outputs a newline character: '\n'.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \r
- </p>
- </td>
- <td>
- <p>
- Outputs a carriage return character: '\r'.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \t
- </p>
- </td>
- <td>
- <p>
- Outputs a tab character: '\t'.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \v
- </p>
- </td>
- <td>
- <p>
- Outputs a vertical tab character: '\v'.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \xDD
- </p>
- </td>
- <td>
- <p>
- Outputs the character whose hexadecimal code point is 0xDD
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \x{DDDD}
- </p>
- </td>
- <td>
- <p>
- Outputs the character whose hexadecimal code point is 0xDDDDD
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \cX
- </p>
- </td>
- <td>
- <p>
- Outputs the ANSI escape sequence "escape-X".
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \D
- </p>
- </td>
- <td>
- <p>
- If D is a decimal digit in the range 1-9, then outputs the text
- that matched sub-expression D.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \l
- </p>
- </td>
- <td>
- <p>
- Causes the next character to be outputted, to be output in lower
- case.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \u
- </p>
- </td>
- <td>
- <p>
- Causes the next character to be outputted, to be output in upper
- case.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \L
- </p>
- </td>
- <td>
- <p>
- Causes all subsequent characters to be output in lower case, until
- a \E is found.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \U
- </p>
- </td>
- <td>
- <p>
- Causes all subsequent characters to be output in upper case, until
- a \E is found.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- \E
- </p>
- </td>
- <td>
- <p>
- Terminates a \L or \U sequence.
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- </div>
- <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
- <td align="left"></td>
- <td align="right"><div class="copyright-footer">Copyright © 1998-2013 John Maddock<p>
- 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" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
- </p>
- </div></td>
- </tr></table>
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