/[pcre]/code/trunk/doc/html/pcrepattern.html

Diff of /code/trunk/doc/html/pcrepattern.html

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-revision 86 by nigel,
Sat Feb 24 21:40:45 2007 UTC
+revision 87 by nigel,
Sat Feb 24 21:41:21 2007 UTC
 Line 175 
 represents:
    \t        tab (hex 09)
    \ddd      character with octal code ddd, or backreference
    \xhh      character with hex code hh
-   \x{hhh..} character with hex code hhh... (UTF-8 mode only)
+   \x{hhh..} character with hex code hhh..
  </pre>
  The precise effect of \cx is as follows: if x is a lower case letter, it
  is converted to upper case. Then bit 6 of the character (hex 40) is inverted.
 Line 184 
 Thus \cz becomes hex 1A, but \c{ becomes
  </P>
  <P>
  After \x, from zero to two hexadecimal digits are read (letters can be in
- upper or lower case). In UTF-8 mode, any number of hexadecimal digits may
+ upper or lower case). Any number of hexadecimal digits may appear between \x{
- appear between \x{ and }, but the value of the character code must be less
+ and }, but the value of the character code must be less than 256 in non-UTF-8
- than 2**31 (that is, the maximum hexadecimal value is 7FFFFFFF). If characters
+ mode, and less than 2**31 in UTF-8 mode (that is, the maximum hexadecimal value
- other than hexadecimal digits appear between \x{ and }, or if there is no
+ is 7FFFFFFF). If characters other than hexadecimal digits appear between \x{
- terminating }, this form of escape is not recognized. Instead, the initial
+ and }, or if there is no terminating }, this form of escape is not recognized.
- \x will be interpreted as a basic hexadecimal escape, with no following
+ Instead, the initial \x will be interpreted as a basic hexadecimal escape,
- digits, giving a character whose value is zero.
+ with no following digits, giving a character whose value is zero.
  </P>
  <P>
  Characters whose value is less than 256 can be defined by either of the two
- syntaxes for \x when PCRE is in UTF-8 mode. There is no difference in the
+ syntaxes for \x. There is no difference in the way they are handled. For
- way they are handled. For example, \xdc is exactly the same as \x{dc}.
+ example, \xdc is exactly the same as \x{dc}.
  </P>
  <P>
  After \0 up to two further octal digits are read. In both cases, if there
 Line 285 
 greater than 128 are used for accented l
  <P>
  In UTF-8 mode, characters with values greater than 128 never match \d, \s, or
  \w, and always match \D, \S, and \W. This is true even when Unicode
- character property support is available.
+ character property support is available. The use of locales with Unicode is
+ discouraged.
  <a name="uniextseq"></a></P>
  <br><b>
  Unicode character properties
  </b><br>
  <P>
  When PCRE is built with Unicode character property support, three additional
- escape sequences to match generic character types are available when UTF-8 mode
+ escape sequences to match character properties are available when UTF-8 mode
  is selected. They are:
  <pre>
-  \p{<i>xx</i>}   a character with the <i>xx</i> property
+   \p{<i>xx</i>}   a character with the <i>xx</i> property
-  \P{<i>xx</i>}   a character without the <i>xx</i> property
+   \P{<i>xx</i>}   a character without the <i>xx</i> property
-  \X       an extended Unicode sequence
+   \X       an extended Unicode sequence
  </pre>
- The property names represented by <i>xx</i> above are limited to the
+ The property names represented by <i>xx</i> above are limited to the Unicode
- Unicode general category properties. Each character has exactly one such
+ script names, the general category properties, and "Any", which matches any
- property, specified by a two-letter abbreviation. For compatibility with Perl,
+ character (including newline). Other properties such as "InMusicalSymbols" are
- negation can be specified by including a circumflex between the opening brace
+ not currently supported by PCRE. Note that \P{Any} does not match any
- and the property name. For example, \p{^Lu} is the same as \P{Lu}.
+ characters, so always causes a match failure.
  </P>
  <P>
- If only one letter is specified with \p or \P, it includes all the properties
+ Sets of Unicode characters are defined as belonging to certain scripts. A
- that start with that letter. In this case, in the absence of negation, the
+ character from one of these sets can be matched using a script name. For
- curly brackets in the escape sequence are optional; these two examples have
+ example:
- the same effect:
+ <pre>
+   \p{Greek}
+   \P{Han}
+ </pre>
+ Those that are not part of an identified script are lumped together as
+ "Common". The current list of scripts is:
+ </P>
+ <P>
+ Arabic,
+ Armenian,
+ Bengali,
+ Bopomofo,
+ Braille,
+ Buginese,
+ Buhid,
+ Canadian_Aboriginal,
+ Cherokee,
+ Common,
+ Coptic,
+ Cypriot,
+ Cyrillic,
+ Deseret,
+ Devanagari,
+ Ethiopic,
+ Georgian,
+ Glagolitic,
+ Gothic,
+ Greek,
+ Gujarati,
+ Gurmukhi,
+ Han,
+ Hangul,
+ Hanunoo,
+ Hebrew,
+ Hiragana,
+ Inherited,
+ Kannada,
+ Katakana,
+ Kharoshthi,
+ Khmer,
+ Lao,
+ Latin,
+ Limbu,
+ Linear_B,
+ Malayalam,
+ Mongolian,
+ Myanmar,
+ New_Tai_Lue,
+ Ogham,
+ Old_Italic,
+ Old_Persian,
+ Oriya,
+ Osmanya,
+ Runic,
+ Shavian,
+ Sinhala,
+ Syloti_Nagri,
+ Syriac,
+ Tagalog,
+ Tagbanwa,
+ Tai_Le,
+ Tamil,
+ Telugu,
+ Thaana,
+ Thai,
+ Tibetan,
+ Tifinagh,
+ Ugaritic,
+ Yi.
+ </P>
+ <P>
+ Each character has exactly one general category property, specified by a
+ two-letter abbreviation. For compatibility with Perl, negation can be specified
+ by including a circumflex between the opening brace and the property name. For
+ example, \p{^Lu} is the same as \P{Lu}.
+ </P>
+ <P>
+ If only one letter is specified with \p or \P, it includes all the general
+ category properties that start with that letter. In this case, in the absence
+ of negation, the curly brackets in the escape sequence are optional; these two
+ examples have the same effect:
  <pre>
    \p{L}
    \pL
  </pre>
- The following property codes are supported:
+ The following general category property codes are supported:
  <pre>
    C     Other
    Cc    Control
-Line 360 
 The following property codes are support
+Line 441 
 The following property codes are support
    Zp    Paragraph separator
    Zs    Space separator
  </pre>
- Extended properties such as "Greek" or "InMusicalSymbols" are not supported by
+ The special property L& is also supported: it matches a character that has
- PCRE.
+ the Lu, Ll, or Lt property, in other words, a letter that is not classified as
+ a modifier or "other".
+ </P>
+ <P>
+ The long synonyms for these properties that Perl supports (such as \p{Letter})
+ are not supported by PCRE. Nor is is permitted to prefix any of these
+ properties with "Is".
+ </P>
+ <P>
+ No character that is in the Unicode table has the Cn (unassigned) property.
+ Instead, this property is assumed for any code point that is not in the
+ Unicode table.
  </P>
  <P>
  Specifying caseless matching does not affect these escape sequences. For
-Line 1360 
 number, provided that it occurs inside t
+Line 1452 
 number, provided that it occurs inside t
  (?R) is a recursive call of the entire regular expression.
  </P>
  <P>
- For example, this PCRE pattern solves the nested parentheses problem (assume
+ A recursive subpattern call is always treated as an atomic group. That is, once
- the PCRE_EXTENDED option is set so that white space is ignored):
+ it has matched some of the subject string, it is never re-entered, even if
+ it contains untried alternatives and there is a subsequent matching failure.
+ </P>
+ <P>
+ This PCRE pattern solves the nested parentheses problem (assume the
+ PCRE_EXTENDED option is set so that white space is ignored):
  <pre>
    \( ( (?&#62;[^()]+) | (?R) )* \)
  </pre>
  First it matches an opening parenthesis. Then it matches any number of
  substrings which can either be a sequence of non-parentheses, or a recursive
- match of the pattern itself (that is a correctly parenthesized substring).
+ match of the pattern itself (that is, a correctly parenthesized substring).
  Finally there is a closing parenthesis.
  </P>
  <P>
-Line 1450 
 is used, it does match "sense and respon
+Line 1547 
 is used, it does match "sense and respon
  strings. Such references must, however, follow the subpattern to which they
  refer.
  </P>
+ <P>
+ Like recursive subpatterns, a "subroutine" call is always treated as an atomic
+ group. That is, once it has matched some of the subject string, it is never
+ re-entered, even if it contains untried alternatives and there is a subsequent
+ matching failure.
+ </P>
  <br><a name="SEC20" href="#TOC1">CALLOUTS</a><br>
  <P>
  Perl has a feature whereby using the sequence (?{...}) causes arbitrary Perl
-Line 1486 
 description of the interface to the call
+Line 1589 
 description of the interface to the call
  documentation.
  </P>
  <P>
- Last updated: 28 February 2005
+ Last updated: 24 January 2006
  <br>
- Copyright &copy; 1997-2005 University of Cambridge.
+ Copyright &copy; 1997-2006 University of Cambridge.
  <p>
  Return to the <a href="index.html">PCRE index page</a>.
  </p>

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