ch05_04.htm

编程珍珠,里面很多好用的代码,大家可以参考学习呵呵,

<td>Reverse when used right-to-left</td>
</tr>


</table>
<p>
<a name="INDEX-1565"></a><a name="INDEX-1566"></a>
The following properties classify various syllabaries according to vowel
sounds:
<blockquote>
<pre class="programlisting">IsSylA         IsSylE         IsSylO         IsSylWAA       IsSylWII
IsSylAA        IsSylEE        IsSylOO        IsSylWC        IsSylWO
IsSylAAI       IsSylI         IsSylU         IsSylWE        IsSylWOO
IsSylAI        IsSylII        IsSylV         IsSylWEE       IsSylWU
IsSylC         IsSylN         IsSylWA        IsSylWI        IsSylWV</pre>
</blockquote>

For example, <tt class="literal">\p{IsSylA}</tt> would match <tt class="literal">\N{KATAKANA LETTER KA}</tt>
but not <tt class="literal">\N{KATAKANA LETTER KU}</tt>.</p>

<p>Now that we've basically told you all these Unicode 3.0 properties, we
should point out that a few of the more esoteric ones aren't
implemented in version 5.6.0 of Perl because its implementation was
based in part on Unicode 2.0, and things like the bidirectional algorithm
were still being worked out.  However, by the time you read this, the
missing properties may well be implemented, so we listed them anyway.</p>




<h3 class="sect3">5.4.3.3. Unicode block properties</h3>

<p>
<a name="INDEX-1567"></a><a name="INDEX-1568"></a><a name="INDEX-1569"></a><a name="INDEX-1570"></a>
Some Unicode properties are of the form
<tt class="literal">\p{In</tt><em class="replaceable">SCRIPT</em><tt class="literal">}</tt>.
(Note the distinction between <tt class="literal">Is</tt> and
<tt class="literal">In</tt>.)  The <tt class="literal">In</tt> properties are for
testing block ranges of a particular
<em class="replaceable">SCRIPT</em>.  If you have a character, and you
wonder whether it were written in Greek script, you could test with:
<blockquote>
<pre class="programlisting">print "It's Greek to me!\n" if chr(931) =~ /\p{InGreek}/;</pre>
</blockquote>

That works by checking whether a character is "in" the valid range of
that script type.  This may be negated with
<tt class="literal">\P{In</tt><em class="replaceable">SCRIPT</em><tt class="literal">}</tt>
to find out whether something <em class="emphasis">isn't</em> in a
particular script's block, such as <tt class="literal">\P{InDingbats}</tt>
to test whether a string contains a non-dingbat.  Block properties
include the following:
<blockquote>
<pre class="programlisting">InArabic       InCyrillic     InHangulJamo   InMalayalam    InSyriac
InArmenian     InDevanagari   InHebrew       InMongolian    InTamil
InArrows       InDingbats     InHiragana     InMyanmar      InTelugu
InBasicLatin   InEthiopic     InKanbun       InOgham        InThaana
InBengali      InGeorgian     InKannada      InOriya        InThai
InBopomofo     InGreek        InKatakana     InRunic        InTibetan
InBoxDrawing   InGujarati     InKhmer        InSinhala      InYiRadicals
InCherokee     InGurmukhi     InLao          InSpecials     InYiSyllables</pre>
</blockquote>

Not to mention jawbreakers like these:
<blockquote>
<pre class="programlisting">InAlphabeticPresentationForms         InHalfwidthandFullwidthForms
InArabicPresentationForms-A           InHangulCompatibilityJamo
InArabicPresentationForms-B           InHangulSyllables
InBlockElements                       InHighPrivateUseSurrogates
InBopomofoExtended                    InHighSurrogates
InBraillePatterns                     InIdeographicDescriptionCharacters
InCJKCompatibility                    InIPAExtensions
InCJKCompatibilityForms               InKangxiRadicals
InCJKCompatibilityIdeographs          InLatin-1Supplement
InCJKRadicalsSupplement               InLatinExtended-A
InCJKSymbolsandPunctuation            InLatinExtended-B
InCJKUnifiedIdeographs                InLatinExtendedAdditional
InCJKUnifiedIdeographsExtensionA      InLetterlikeSymbols
InCombiningDiacriticalMarks           InLowSurrogates
InCombiningHalfMarks                  InMathematicalOperators
InCombiningMarksforSymbols            InMiscellaneousSymbols
InControlPictures                     InMiscellaneousTechnical
InCurrencySymbols                     InNumberForms
InEnclosedAlphanumerics               InOpticalCharacterRecognition
InEnclosedCJKLettersandMonths         InPrivateUse
InGeneralPunctuation                  InSuperscriptsandSubscripts
InGeometricShapes                     InSmallFormVariants
InGreekExtended                       InSpacingModifierLetters</pre>
</blockquote>

And the winner is:
<blockquote>
<pre class="programlisting">InUnifiedCanadianAboriginalSyllabics</pre>
</blockquote>

See
<em class="replaceable">PATH_TO_PERLLIB</em><em class="emphasis">/unicode/In/*.pl</em>
to get an up-to-date listing of all of these character block
properties.  Note that these <tt class="literal">In</tt> properties are only
testing to see if the character is in the block of characters
allocated for that script.  There is no guarantee that all

characters in that range are defined; you also need to test
against one of the <tt class="literal">Is</tt> properties discussed earlier
to see if the character is defined.  There is also no guarantee that a
particular language doesn't use characters outside its assigned block.
In particular, many European languages mix extended Latin characters
with Latin-1 characters.</p>

<p>But hey, if you need a particular property that isn't provided, that's
not a big problem.  Read on.</p>




<h3 class="sect3">5.4.3.4. Defining your own character properties</h3>

<p>
<a name="INDEX-1571"></a><a name="INDEX-1572"></a>
To define your own property, you need to write a subroutine with the
name of the property you want (see <a href="ch06_01.htm">Chapter 6, "Subroutines"</a>).  The subroutine should be defined
in the package that needs the property (see <a href="ch10_01.htm">Chapter 10, "Packages"</a>), which means that if you want to use
it in multiple packages, you'll either have to import it from a module
(see <a href="ch11_01.htm">Chapter 11, "Modules"</a>), or inherit it as a class
method from the package in which it is defined (see
<a href="ch12_01.htm">Chapter 12, "Objects"</a>).</p>

<p>Once you've got that all settled, the subroutine should return data in
the same format as the files in <em class="replaceable">PATH_TO_PERLLIB</em><em class="emphasis">/unicode/Is</em>
directory.  That is, just return a list of characters or character ranges in
hexadecimal, one per line.  If there is a range, the two numbers are
separated by a tab.  Suppose you wanted a property that would be true
if your character is in the range of either of the Japanese
syllabaries, known as hiragana and katakana.  (Together they're known
as kana).  You can just put in the two ranges like this:
<blockquote>
<pre class="programlisting">sub InKana {
    return &lt;&lt;'END';
3040    309F
30A0    30FF
END
}</pre>
</blockquote>

Alternatively, you could define it in terms of existing property names:
<blockquote>
<pre class="programlisting">sub InKana {
    return &lt;&lt;'END';
+utf8::InHiragana
+utf8::InKatakana
END
}</pre>
</blockquote>
<a name="INDEX-1573"></a><a name="INDEX-1574"></a>
You can also do set subtraction using a "<tt class="literal">-</tt>" prefix.  Suppose you
only wanted the actual characters, not just the block ranges of characters.
You could weed out all the undefined ones like this:
<blockquote>
<pre class="programlisting">sub IsKana {
    return &lt;&lt;'END';
+utf8::InHiragana
+utf8::InKatakana
-utf8::IsCn
END
}</pre>
</blockquote>
<a name="INDEX-1575"></a>
You can also start with a complemented character set using the "<tt class="literal">!</tt>" prefix:
<blockquote>
<pre class="programlisting">sub IsNotKana {
    return &lt;&lt;'END';
!utf8::InHiragana
-utf8::InKatakana
+utf8::IsCn
END
}</pre>
</blockquote>
<a name="INDEX-1576"></a>
Perl itself uses exactly the same tricks to define the meanings of its
"classic" character classes (like <tt class="literal">\w</tt>) when you include them in your
own custom character classes (like <tt class="literal">[-.\w\s]</tt>).  You might think that
the more complicated you get with your rules, the slower they will run,
but in fact, once Perl has calculated the bit pattern for a particular
64-bit swatch of your property, it caches it so it never has to
recalculate the pattern again.  (It does it in 64-bit swatches so that it
doesn't even have to decode your utf8 to do its lookups.)  Thus, all
character classes, built-in or custom, run at essentially the same
speed (fast) once they get going.</p>

<a name="INDEX-1577"></a><a name="INDEX-1578"></a>







<h3 class="sect2">5.4.4. POSIX-Style Character Classes</h3>

<p>
<a name="INDEX-1579"></a><a name="INDEX-1580"></a>
Unlike Perl's other character class shortcuts, the POSIX-style
character-class syntax notation, <tt class="literal">[:</tt><em class="replaceable">CLASS</em><tt class="literal">:]</tt>, is available for use
<em class="emphasis">only</em> when constructing other character classes, that is, inside an
additional pair of square brackets.  For example,
<tt class="literal">/[.,[:alpha:][:digit:]]/</tt> will search for one character that is
either a literal dot (because it's in a character class), a comma, an
alphabetic character, or a digit.</p>

<p>The POSIX classes available as of revision 5.6 of Perl are shown in
<a href="ch05_04.htm#perl3-tab-posix-char-class">Table 5-11</a>.</p>

<a name="perl3-tab-posix-char-class"></a>
<h4 class="objtitle">Table 5.11. POSIX Character Classes</h4>
<table border="1">

<tr>
<th>Class</th>
<th>Meaning</th>
</tr>




<tr>
<td><tt class="literal">alnum</tt></td>
<td>
<p>Any alphanumeric, that is, an <tt class="literal">alpha</tt> or a <tt class="literal">digit</tt>.</p>
</td>
</tr>

<tr>
<td><tt class="literal">alpha</tt></td>
<td>
<p>Any letter.  (That's a lot more letters than you think, unless you're
thinking Unicode, in which case it's still a lot.)</p>
</td>
</tr>

<tr>
<td><tt class="literal">ascii</tt></td>
<td>Any character with an ordinal value between 0 and 127.</td>
</tr>

<tr>
<td><tt class="literal">cntrl</tt></td>
<td>
<p>Any control character.  Usually characters that don't produce output
as such, but instead control the terminal somehow; for example,
newline, form feed, and backspace are all control characters. Characters with an <tt class="literal">ord</tt> value less than 32 are most often classified
as control characters.</p>
</td>
</tr>

<tr>
<td><tt class="literal">digit</tt></td>
<td>
<p> A character
representing a decimal digit, such as <tt class="literal">0</tt> to
<tt class="literal">9</tt>.  (Includes other characters under Unicode.)
Equivalent to <tt class="literal">\d</tt>.</p>
</td>
</tr>

<tr>
<td><tt class="literal">graph</tt></td>
<td>
<p>Any alphanumeric or punctuation character.</p>
</td>
</tr>

<tr>
<td><tt class="literal">lower</tt></td>
<td>
<p>A lowercase letter.</p>
</td>
</tr>

<tr>
<td><tt class="literal">print</tt></td>
<td>
<p>Any alphanumeric or punctuation character or space.</p>
</td>
</tr>

<tr>
<td><tt class="literal">punct</tt></td>
<td>
<p>Any punctuation character.</p>
</td>
</tr>

<tr>
<td><tt class="literal">space</tt></td>
<td>
<p>Any space character.  Includes tab, newline, form feed, and carriage return
(and a lot more under Unicode.)  Equivalent to <tt class="literal">\s</tt>.</p>
</td>
</tr>

<tr>
<td><tt class="literal">upper</tt></td>
<td>
<p>Any uppercase (or titlecase) letter.</p>
</td>
</tr>

<tr>
<td><tt class="literal">word</tt></td>
<td>
<p>Any identifier character, either an <tt class="literal">alnum</tt> or underline.</p>
</td>
</tr>

<tr>
<td><tt class="literal">xdigit</tt></td>
<td>
<p>Any hexadecimal digit.  Though this may seem silly (<tt class="literal">[0-9a-fA-F]</tt>
works just fine), it is included for completeness.</p>
</td>
</tr>


</table>

<p>
<a name="INDEX-1581"></a>
You can negate the POSIX character classes by prefixing the class
name with a <tt class="literal">^</tt> following the <tt class="literal">[:</tt>.  (This is a Perl extension.)
For example:</p>

<a name="perl3-tab-posixtrad"></a>
<table border="1">

<tr>
<th>POSIX</th>
<th>Classic</th>
</tr>




<tr>
<td><tt class="literal">[:^digit:]</tt></td>
<td><tt class="literal">\D</tt></td>
</tr>

<tr>
<td><tt class="literal">[:^space:]</tt></td>
<td><tt class="literal">\S</tt></td>
</tr>

<tr>
<td><tt class="literal">[:^word:]</tt></td>
<td><tt class="literal">\W</tt></td>
</tr>


</table>
<p>If the <tt class="literal">use utf8</tt> pragma is not requested, but the
<tt class="literal">use locale</tt> pragma is, the classes correlate
directly with the equivalent functions in the C library's
<em class="emphasis">isalpha</em>(3) interface (except for
<tt class="literal">word</tt>, which is a Perl extension, mirroring
<tt class="literal">\w</tt>).
<a name="INDEX-1582"></a>
</p>

<p>If the <tt class="literal">utf8</tt> pragma is used, POSIX character classes
are exactly equivalent to the corresponding <tt class="literal">Is</tt>
properties listed in <a href="ch05_04.htm#perl3-tab-prop-composite">Table 5-9</a>.  For
example <tt class="literal">[:lower:]</tt> and <tt class="literal">\p{Lower}</tt>
are equivalent, except that the POSIX classes may only be used within
constructed character classes, whereas Unicode properties have no such
restriction and may be used in patterns wherever Perl shortcuts like
<tt class="literal">\s</tt> and <tt class="literal">\w</tt> may be used.</p>

<p>The brackets are part of the POSIX-style <tt class="literal">[::]</tt> construct,
not part of the whole character class.  This leads to writing
patterns like <tt class="literal">/^[[:lower:][:digit:]]+$/</tt>, to match a string
consisting entirely of lowercase letters or digits (plus an
optional trailing newline).  In particular, this does not work:
<blockquote>
<pre class="programlisting">42 =~ /^[:digit:]$/         # WRONG</pre>
</blockquote>

That's because it's not inside a character class.  Rather, it <em class="emphasis">is</em> a
character class, the one representing the characters "<tt class="literal">:</tt>", "<tt class="literal">i</tt>",
"<tt class="literal">t</tt>", "<tt class="literal">g</tt>", and "<tt class="literal">d</tt>".  Perl doesn't care that you specified
"<tt class="literal">:</tt>" twice.</p>

<p>Here's what you need instead:
<blockquote>
<pre class="programlisting">42 =~ /^[[:digit:]]+$/</pre>
</blockquote>

The POSIX character classes <tt class="literal">[.cc.]</tt> and
<tt class="literal">[=cc=]</tt> are recognized but produce an error
indicating they are not supported.  Trying to use
<em class="emphasis">any</em> POSIX character class in older verions of
Perl is likely to fail miserably, and perhaps even silently.  If
you're going to use POSIX character classes, it's best to require a
new version of Perl by saying:
<blockquote>
<pre class="programlisting">use 5.6.0;</pre>
</blockquote>
</p>

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