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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_regex.ref.syntax_option_type.syntax_option_type_extended"></a><a class="link" href="syntax_option_type_extended.html" title="Options for POSIX Extended Regular Expressions">
Options for POSIX Extended Regular Expressions</a>
</h4></div></div></div>
<p>
Exactly one of the following must always be set for <a class="link" href="../../syntax/basic_extended.html" title="POSIX Extended Regular Expression Syntax">POSIX
extended regular expressions</a>:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Element
</p>
</th>
<th>
<p>
Standardized
</p>
</th>
<th>
<p>
Effect when set
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
extended
</p>
</td>
<td>
<p>
Yes
</p>
</td>
<td>
<p>
Specifies that the grammar recognized by the regular expression
engine is the same as that used by POSIX extended regular expressions
in IEEE Std 1003.1-2001, Portable Operating System Interface
(POSIX ), Base Definitions and Headers, Section 9, Regular Expressions
(FWD.1).
</p>
<p>
Refer to the <a class="link" href="../../syntax/basic_extended.html" title="POSIX Extended Regular Expression Syntax">POSIX
extended regular expression guide</a> for more information.
</p>
<p>
In addition some perl-style escape sequences are supported (The
POSIX standard specifies that only "special" characters
may be escaped, all other escape sequences result in undefined
behavior).
</p>
</td>
</tr>
<tr>
<td>
<p>
egrep
</p>
</td>
<td>
<p>
Yes
</p>
</td>
<td>
<p>
Specifies that the grammar recognized by the regular expression
engine is the same as that used by POSIX utility grep when given
the -E option in IEEE Std 1003.1-2001, Portable Operating System
Interface (POSIX ), Shells and Utilities, Section 4, Utilities,
grep (FWD.1).
</p>
<p>
That is to say, the same as <a class="link" href="../../syntax/basic_extended.html" title="POSIX Extended Regular Expression Syntax">POSIX
extended syntax</a>, but with the newline character acting
as an alternation character in addition to "|".
</p>
</td>
</tr>
<tr>
<td>
<p>
awk
</p>
</td>
<td>
<p>
Yes
</p>
</td>
<td>
<p>
Specifies that the grammar recognized by the regular expression
engine is the same as that used by POSIX utility awk in IEEE
Std 1003.1-2001, Portable Operating System Interface (POSIX ),
Shells and Utilities, Section 4, awk (FWD.1).
</p>
<p>
That is to say: the same as <a class="link" href="../../syntax/basic_extended.html" title="POSIX Extended Regular Expression Syntax">POSIX
extended syntax</a>, but with escape sequences in character
classes permitted.
</p>
<p>
In addition some perl-style escape sequences are supported (actually
the awk syntax only requires \a \b \t \v \f \n and \r to be recognised,
all other Perl-style escape sequences invoke undefined behavior
according to the POSIX standard, but are in fact recognised by
Boost.Regex).
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
The following options may also be set when using POSIX extended regular
expressions:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Element
</p>
</th>
<th>
<p>
Standardized
</p>
</th>
<th>
<p>
Effect when set
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
icase
</p>
</td>
<td>
<p>
Yes
</p>
</td>
<td>
<p>
Specifies that matching of regular expressions against a character
container sequence shall be performed without regard to case.
</p>
</td>
</tr>
<tr>
<td>
<p>
nosubs
</p>
</td>
<td>
<p>
Yes
</p>
</td>
<td>
<p>
Specifies that when a regular expression is matched against a
character container sequence, then no sub-expression matches
are to be stored in the supplied <a class="link" href="../match_results.html" title="match_results"><code class="computeroutput"><span class="identifier">match_results</span></code></a> structure.
</p>
</td>
</tr>
<tr>
<td>
<p>
optimize
</p>
</td>
<td>
<p>
Yes
</p>
</td>
<td>
<p>
Specifies that the regular expression engine should pay more
attention to the speed with which regular expressions are matched,
and less to the speed with which regular expression objects are
constructed. Otherwise it has no detectable effect on the program
output. This currently has no effect for Boost.Regex.
</p>
</td>
</tr>
<tr>
<td>
<p>
collate
</p>
</td>
<td>
<p>
Yes
</p>
</td>
<td>
<p>
Specifies that character ranges of the form <code class="computeroutput"><span class="special">[</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">b</span><span class="special">]</span></code>
should be locale sensitive. This bit is on by default for POSIX-Extended
regular expressions, but can be unset to force ranges to be compared
by code point only.
</p>
</td>
</tr>
<tr>
<td>
<p>
newline_alt
</p>
</td>
<td>
<p>
No
</p>
</td>
<td>
<p>
Specifies that the \n character has the same effect as the alternation
operator |. Allows newline separated lists to be used as a list
of alternatives.
</p>
</td>
</tr>
<tr>
<td>
<p>
no_escape_in_lists
</p>
</td>
<td>
<p>
No
</p>
</td>
<td>
<p>
When set this makes the escape character ordinary inside lists,
so that <code class="computeroutput"><span class="special">[\</span><span class="identifier">b</span><span class="special">]</span></code> would match either '\' or 'b'.
This bit is on by default for POSIX-Extended regular expressions,
but can be unset to force escapes to be recognised inside lists.
</p>
</td>
</tr>
<tr>
<td>
<p>
no_bk_refs
</p>
</td>
<td>
<p>
No
</p>
</td>
<td>
<p>
When set then backreferences are disabled. This bit is on by
default for POSIX-Extended regular expressions, but can be unset
to support for backreferences on.
</p>
</td>
</tr>
<tr>
<td>
<p>
no_except
</p>
</td>
<td>
<p>
No
</p>
</td>
<td>
<p>
Prevents <a class="link" href="../basic_regex.html" title="basic_regex"><code class="computeroutput"><span class="identifier">basic_regex</span></code></a> from throwing
an exception when an invalid expression is encountered.
</p>
</td>
</tr>
<tr>
<td>
<p>
save_subexpression_location
</p>
</td>
<td>
<p>
No
</p>
</td>
<td>
<p>
When set then the locations of individual sub-expressions within
the <span class="emphasis"><em>original regular expression string</em></span> can
be accessed via the <a class="link" href="../basic_regex.html#boost_regex.basic_regex.subexpression"><code class="computeroutput"><span class="identifier">subexpression</span><span class="special">()</span></code></a>
member function of <code class="computeroutput"><span class="identifier">basic_regex</span></code>.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 1998 -2007 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>
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