Update the Mac OS X situation.

[p5sagit/p5-mst-13.2.git] / pod / perlunicode.pod

diff --git a/pod/perlunicode.pod b/pod/perlunicode.pod
index af79344..d2c48e2 100644 (file)
--- a/pod/perlunicode.pod
+++ b/pod/perlunicode.pod
@@ -615,6 +615,91 @@ And finally, C<scalar reverse()> reverses by character rather than by byte.
 
 =back
 
+=head2 User-defined Character Properties
+
+You can define your own character properties by defining subroutines
+that have names beginning with "In" or "Is".  The subroutines must be
+visible in the package that uses the properties.  The user-defined
+properties can be used in the regular expression C<\p> and C<\P>
+constructs.
+
+The subroutines must return a specially formatted string: one or more
+newline-separated lines.  Each line must be one of the following:
+
+=over 4
+
+=item *
+
+Two hexadecimal numbers separated by horizontal whitespace (space or
+tabulator characters) denoting a range of Unicode codepoints to include.
+
+=item *
+
+Something to include, prefixed by "+": either an built-in character
+property (prefixed by "utf8::"), for all the characters in that
+property; or two hexadecimal codepoints for a range; or a single
+hexadecimal codepoint.
+
+=item *
+
+Something to exclude, prefixed by "-": either an existing character
+property (prefixed by "utf8::"), for all the characters in that
+property; or two hexadecimal codepoints for a range; or a single
+hexadecimal codepoint.
+
+=item *
+
+Something to negate, prefixed "!": either an existing character
+property (prefixed by "utf8::") for all the characters except the
+characters in the property; or two hexadecimal codepoints for a range;
+or a single hexadecimal codepoint.
+
+=back
+
+For example, to define a property that covers both the Japanese
+syllabaries (hiragana and katakana), you can define
+
+    sub InKana {
+       return <<END;
+    3040\t309F
+    30A0\t30FF
+    END
+    }
+
+Imagine that the here-doc end marker is at the beginning of the line.
+Now you can use C<\p{InKana}> and C<\P{InKana}>.
+
+You could also have used the existing block property names:
+
+    sub InKana {
+       return <<'END';
+    +utf8::InHiragana
+    +utf8::InKatakana
+    END
+    }
+
+Suppose you wanted to match only the allocated characters,
+not the raw block ranges: in other words, you want to remove
+the non-characters:
+
+    sub InKana {
+       return <<'END';
+    +utf8::InHiragana
+    +utf8::InKatakana
+    -utf8::IsCn
+    END
+    }
+
+The negation is useful for defining (surprise!) negated classes.
+
+    sub InNotKana {
+       return <<'END';
+    !utf8::InHiragana
+    -utf8::InKatakana
+    +utf8::IsCn
+    END
+    }
+
 =head2 Character encodings for input and output
 
 See L<Encode>.
@@ -645,7 +730,8 @@ Level 1 - Basic Unicode Support
         [ 3] . \p{...} \P{...}
         [ 4] now scripts (see UTR#24 Script Names) in addition to blocks
         [ 5] have negation
-        [ 6] can use look-ahead to emulate subtraction (*)
+        [ 6] can use regular expression look-ahead [a]
+             or user-defined character properties [b] to emulate subtraction
         [ 7] include Letters in word characters
         [ 8] note that perl does Full casefolding in matching, not Simple:
              for example U+1F88 is equivalent with U+1F000 U+03B9,
@@ -658,7 +744,7 @@ Level 1 - Basic Unicode Support
              (should also affect <>, $., and script line numbers)
              (the \x{85}, \x{2028} and \x{2029} do match \s)
 
-(*) You can mimic class subtraction using lookahead.
+[a] You can mimic class subtraction using lookahead.
 For example, what TR18 might write as
 
     [{Greek}-[{UNASSIGNED}]]
@@ -674,6 +760,8 @@ But in this particular example, you probably really want
 
 which will match assigned characters known to be part of the Greek script.
 
+[b] See L</User-defined Character Properties>.
+
 =item *
 
 Level 2 - Extended Unicode Support
@@ -828,8 +916,9 @@ needed.  The BOM signatures will be 0x00 0x00 0xFE 0xFF for BE and
 UCS-2, UCS-4
 
 Encodings defined by the ISO 10646 standard.  UCS-2 is a 16-bit
-encoding, UCS-4 is a 32-bit encoding.  Unlike UTF-16, UCS-2
-is not extensible beyond 0xFFFF, because it does not use surrogates.
+encoding.  Unlike UTF-16, UCS-2 is not extensible beyond 0xFFFF,
+because it does not use surrogates.  UCS-4 is a 32-bit encoding,
+functionally identical to UTF-32.
 
 =item *