implement the Unicode standard or the accompanying technical reports
from cover to cover, Perl does support many Unicode features.
+People who want to learn to use Unicode in Perl, should probably read
+L<the Perl Unicode tutorial|perlunitut> before reading this reference
+document.
+
=over 4
-=item Input and Output Disciplines
+=item Input and Output Layers
Perl knows when a filehandle uses Perl's internal Unicode encodings
-(UTF-8 or UTF-EBCDIC) if the filehandle is opened with the ":utf8"
-layer. Other encodings can be converted to Perl's encoding on input
-or from Perl's encoding on output by use of the ":encoding(...)"
-layer. See L<open>.
+(UTF-8, or UTF-EBCDIC if in EBCDIC) if the filehandle is opened with
+the ":utf8" layer. Other encodings can be converted to Perl's
+encoding on input or from Perl's encoding on output by use of the
+":encoding(...)" layer. See L<open>.
-To indicate that Perl source itself is using a particular encoding,
-see L<encoding>.
+To indicate that Perl source itself is in UTF-8, use C<use utf8;>.
=item Regular Expressions
The regular expression compiler produces polymorphic opcodes. That is,
the pattern adapts to the data and automatically switches to the Unicode
-character scheme when presented with Unicode data--or instead uses
-a traditional byte scheme when presented with byte data.
+character scheme when presented with data that is internally encoded in
+UTF-8 -- or instead uses a traditional byte scheme when presented with
+byte data.
=item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts
As a compatibility measure, the C<use utf8> pragma must be explicitly
included to enable recognition of UTF-8 in the Perl scripts themselves
-on ASCII-based machines or to recognize UTF-EBCDIC on EBCDIC-based
+(in string or regular expression literals, or in identifier names) on
+ASCII-based machines or to recognize UTF-EBCDIC on EBCDIC-based
machines. B<These are the only times when an explicit C<use utf8>
-is needed.>
+is needed.> See L<utf8>.
+
+=item BOM-marked scripts and UTF-16 scripts autodetected
+
+If a Perl script begins marked with the Unicode BOM (UTF-16LE, UTF16-BE,
+or UTF-8), or if the script looks like non-BOM-marked UTF-16 of either
+endianness, Perl will correctly read in the script as Unicode.
+(BOMless UTF-8 cannot be effectively recognized or differentiated from
+ISO 8859-1 or other eight-bit encodings.)
+
+=item C<use encoding> needed to upgrade non-Latin-1 byte strings
+
+By default, there is a fundamental asymmetry in Perl's unicode model:
+implicit upgrading from byte strings to Unicode strings assumes that
+they were encoded in I<ISO 8859-1 (Latin-1)>, but Unicode strings are
+downgraded with UTF-8 encoding. This happens because the first 256
+codepoints in Unicode happens to agree with Latin-1.
-You can also use the C<encoding> pragma to change the default encoding
-of the data in your script; see L<encoding>.
+See L</"Byte and Character Semantics"> for more details.
=back
external programs, from information provided by the system (such as %ENV),
or from literals and constants in the source text.
-On Windows platforms, if the C<-C> command line switch is used or the
-${^WIDE_SYSTEM_CALLS} global flag is set to C<1>, all system calls
-will use the corresponding wide-character APIs. This feature is
-available only on Windows to conform to the API standard already
-established for that platform.
-
The C<bytes> pragma will always, regardless of platform, force byte
semantics in a particular lexical scope. See L<bytes>.
for Unicode data and byte semantics for non-Unicode data.
The decision to use character semantics is made transparently. If
input data comes from a Unicode source--for example, if a character
-encoding discipline is added to a filehandle or a literal Unicode
+encoding layer is added to a filehandle or a literal Unicode
string constant appears in a program--character semantics apply.
Otherwise, byte semantics are in effect. The C<bytes> pragma should
be used to force byte semantics on Unicode data.
If strings operating under byte semantics and strings with Unicode
-character data are concatenated, the new string will be upgraded to
-I<ISO 8859-1 (Latin-1)>, even if the old Unicode string used EBCDIC.
-This translation is done without regard to the system's native 8-bit
-encoding, so to change this for systems with non-Latin-1 and
-non-EBCDIC native encodings use the C<encoding> pragma. See
-L<encoding>.
+character data are concatenated, the new string will be created by
+decoding the byte strings as I<ISO 8859-1 (Latin-1)>, even if the
+old Unicode string used EBCDIC. This translation is done without
+regard to the system's native 8-bit encoding.
Under character semantics, many operations that formerly operated on
bytes now operate on characters. A character in Perl is
Strings--including hash keys--and regular expression patterns may
contain characters that have an ordinal value larger than 255.
-If you use a Unicode editor to edit your program, Unicode characters
-may occur directly within the literal strings in one of the various
-Unicode encodings (UTF-8, UTF-EBCDIC, UCS-2, etc.), but will be recognized
-as such and converted to Perl's internal representation only if the
-appropriate L<encoding> is specified.
+If you use a Unicode editor to edit your program, Unicode characters may
+occur directly within the literal strings in UTF-8 encoding, or UTF-16.
+(The former requires a BOM or C<use utf8>, the latter requires a BOM.)
Unicode characters can also be added to a string by using the C<\x{...}>
-notation. The Unicode code for the desired character, in
-hexadecimal, should be placed in the braces. For instance, a smiley
-face is C<\x{263A}>. This encoding scheme only works for characters
-with a code of 0x100 or above.
+notation. The Unicode code for the desired character, in hexadecimal,
+should be placed in the braces. For instance, a smiley face is
+C<\x{263A}>. This encoding scheme only works for all characters, but
+for characters under 0x100, note that Perl may use an 8 bit encoding
+internally, for optimization and/or backward compatibility.
Additionally, if you
use charnames ':full';
-you can use the C<\N{...}> notation and put the official Unicode character
-name within the braces, such as C<\N{WHITE SMILING FACE}>.
-
+you can use the C<\N{...}> notation and put the official Unicode
+character name within the braces, such as C<\N{WHITE SMILING FACE}>.
=item *
=item *
-Regular expressions match characters instead of bytes.
-"." matches a character instead of a byte. The C<\C> pattern
-is provided to force a match a single byte--a "C<char>" in C, hence C<\C>.
+Regular expressions match characters instead of bytes. "." matches
+a character instead of a byte.
=item *
Character classes in regular expressions match characters instead of
bytes and match against the character properties specified in the
-Unicode properties database. C<\w> can be used to match an
+Unicode properties database. C<\w> can be used to match a Japanese
ideograph, for instance.
=item *
Named Unicode properties, scripts, and block ranges may be used like
character classes via the C<\p{}> "matches property" construct and
-the C<\P{}> negation, "doesn't match property".
-For instance, C<\p{Lu}> matches any
-character with the Unicode "Lu" (Letter, uppercase) property, while
-C<\p{M}> matches any character with an "M" (mark--accents and such)
-property. Brackets are not required for single letter properties, so
-C<\p{M}> is equivalent to C<\pM>. Many predefined properties are
-available, such as C<\p{Mirrored}> and C<\p{Tibetan}>.
+the C<\P{}> negation, "doesn't match property".
+
+See L</"Unicode Character Properties"> for more details.
+
+You can define your own character properties and use them
+in the regular expression with the C<\p{}> or C<\P{}> construct.
+
+See L</"User-Defined Character Properties"> for more details.
+
+=item *
+
+The special pattern C<\X> matches any extended Unicode
+sequence--"a combining character sequence" in Standardese--where the
+first character is a base character and subsequent characters are mark
+characters that apply to the base character. C<\X> is equivalent to
+C<(?:\PM\pM*)>.
+
+=item *
+
+The C<tr///> operator translates characters instead of bytes. Note
+that the C<tr///CU> functionality has been removed. For similar
+functionality see pack('U0', ...) and pack('C0', ...).
+
+=item *
+
+Case translation operators use the Unicode case translation tables
+when character input is provided. Note that C<uc()>, or C<\U> in
+interpolated strings, translates to uppercase, while C<ucfirst>,
+or C<\u> in interpolated strings, translates to titlecase in languages
+that make the distinction.
+
+=item *
+
+Most operators that deal with positions or lengths in a string will
+automatically switch to using character positions, including
+C<chop()>, C<chomp()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>,
+C<sprintf()>, C<write()>, and C<length()>. An operator that
+specifically does not switch is C<vec()>. Operators that really don't
+care include operators that treat strings as a bucket of bits such as
+C<sort()>, and operators dealing with filenames.
+
+=item *
+
+The C<pack()>/C<unpack()> letter C<C> does I<not> change, since it is often
+used for byte-oriented formats. Again, think C<char> in the C language.
+
+There is a new C<U> specifier that converts between Unicode characters
+and code points. There is also a C<W> specifier that is the equivalent of
+C<chr>/C<ord> and properly handles character values even if they are above 255.
+
+=item *
+
+The C<chr()> and C<ord()> functions work on characters, similar to
+C<pack("W")> and C<unpack("W")>, I<not> C<pack("C")> and
+C<unpack("C")>. C<pack("C")> and C<unpack("C")> are methods for
+emulating byte-oriented C<chr()> and C<ord()> on Unicode strings.
+While these methods reveal the internal encoding of Unicode strings,
+that is not something one normally needs to care about at all.
+
+=item *
+
+The bit string operators, C<& | ^ ~>, can operate on character data.
+However, for backward compatibility, such as when using bit string
+operations when characters are all less than 256 in ordinal value, one
+should not use C<~> (the bit complement) with characters of both
+values less than 256 and values greater than 256. Most importantly,
+DeMorgan's laws (C<~($x|$y) eq ~$x&~$y> and C<~($x&$y) eq ~$x|~$y>)
+will not hold. The reason for this mathematical I<faux pas> is that
+the complement cannot return B<both> the 8-bit (byte-wide) bit
+complement B<and> the full character-wide bit complement.
+
+=item *
+
+lc(), uc(), lcfirst(), and ucfirst() work for the following cases:
+
+=over 8
+
+=item *
+
+the case mapping is from a single Unicode character to another
+single Unicode character, or
+
+=item *
+
+the case mapping is from a single Unicode character to more
+than one Unicode character.
+
+=back
+
+Things to do with locales (Lithuanian, Turkish, Azeri) do B<not> work
+since Perl does not understand the concept of Unicode locales.
+
+See the Unicode Technical Report #21, Case Mappings, for more details.
+
+But you can also define your own mappings to be used in the lc(),
+lcfirst(), uc(), and ucfirst() (or their string-inlined versions).
+
+See L</"User-Defined Case Mappings"> for more details.
+
+=back
+
+=over 4
+
+=item *
+
+And finally, C<scalar reverse()> reverses by character rather than by byte.
+
+=back
+
+=head2 Unicode Character Properties
+
+Named Unicode properties, scripts, and block ranges may be used like
+character classes via the C<\p{}> "matches property" construct and
+the C<\P{}> negation, "doesn't match property".
+
+For instance, C<\p{Lu}> matches any character with the Unicode "Lu"
+(Letter, uppercase) property, while C<\p{M}> matches any character
+with an "M" (mark--accents and such) property. Brackets are not
+required for single letter properties, so C<\p{M}> is equivalent to
+C<\pM>. Many predefined properties are available, such as
+C<\p{Mirrored}> and C<\p{Tibetan}>.
The official Unicode script and block names have spaces and dashes as
separators, but for convenience you can use dashes, spaces, or
-underbars, and case is unimportant. It is
-recommended, however, that for consistency you use the following naming:
-the official Unicode script, property, or block name (see below for the
-additional rules that apply to block names) with whitespace and dashes
-removed, and the words "uppercase-first-lowercase-rest". "C<Latin-1
-Supplement>" thus becomes "C<Latin1Supplement>".
+underbars, and case is unimportant. It is recommended, however, that
+for consistency you use the following naming: the official Unicode
+script, property, or block name (see below for the additional rules
+that apply to block names) with whitespace and dashes removed, and the
+words "uppercase-first-lowercase-rest". C<Latin-1 Supplement> thus
+becomes C<Latin1Supplement>.
You can also use negation in both C<\p{}> and C<\P{}> by introducing a caret
(^) between the first brace and the property name: C<\p{^Tamil}> is
equal to C<\P{Tamil}>.
+B<NOTE: the properties, scripts, and blocks listed here are as of
+Unicode 5.0.0 in July 2006.>
+
+=over 4
+
+=item General Category
+
Here are the basic Unicode General Category properties, followed by their
-long form. You can use either; C<\p{Lu}> and C<\p{LowercaseLetter}>,
+long form. You can use either; C<\p{Lu}> and C<\p{UppercaseLetter}>,
for instance, are identical.
Short Long
L Letter
+ LC CasedLetter
Lu UppercaseLetter
Ll LowercaseLetter
Lt TitlecaseLetter
Single-letter properties match all characters in any of the
two-letter sub-properties starting with the same letter.
-C<L&> is a special case, which is an alias for C<Ll>, C<Lu>, and C<Lt>.
+C<LC> and C<L&> are special cases, which are aliases for the set of
+C<Ll>, C<Lu>, and C<Lt>.
Because Perl hides the need for the user to understand the internal
-representation of Unicode characters, there is no need to implement the
-somewhat messy concept of surrogates. C<Cs> is therefore not
+representation of Unicode characters, there is no need to implement
+the somewhat messy concept of surrogates. C<Cs> is therefore not
supported.
+=item Bidirectional Character Types
+
Because scripts differ in their directionality--Hebrew is
-written right to left, for example--Unicode supplies these properties:
+written right to left, for example--Unicode supplies these properties in
+the BidiClass class:
Property Meaning
- BidiL Left-to-Right
- BidiLRE Left-to-Right Embedding
- BidiLRO Left-to-Right Override
- BidiR Right-to-Left
- BidiAL Right-to-Left Arabic
- BidiRLE Right-to-Left Embedding
- BidiRLO Right-to-Left Override
- BidiPDF Pop Directional Format
- BidiEN European Number
- BidiES European Number Separator
- BidiET European Number Terminator
- BidiAN Arabic Number
- BidiCS Common Number Separator
- BidiNSM Non-Spacing Mark
- BidiBN Boundary Neutral
- BidiB Paragraph Separator
- BidiS Segment Separator
- BidiWS Whitespace
- BidiON Other Neutrals
-
-For example, C<\p{BidiR}> matches characters that are normally
+ L Left-to-Right
+ LRE Left-to-Right Embedding
+ LRO Left-to-Right Override
+ R Right-to-Left
+ AL Right-to-Left Arabic
+ RLE Right-to-Left Embedding
+ RLO Right-to-Left Override
+ PDF Pop Directional Format
+ EN European Number
+ ES European Number Separator
+ ET European Number Terminator
+ AN Arabic Number
+ CS Common Number Separator
+ NSM Non-Spacing Mark
+ BN Boundary Neutral
+ B Paragraph Separator
+ S Segment Separator
+ WS Whitespace
+ ON Other Neutrals
+
+For example, C<\p{BidiClass:R}> matches characters that are normally
written right to left.
-=back
-
-=head2 Scripts
+=item Scripts
The script names which can be used by C<\p{...}> and C<\P{...}>,
such as in C<\p{Latin}> or C<\p{Cyrillic}>, are as follows:
Arabic
Armenian
+ Balinese
Bengali
Bopomofo
+ Braille
+ Buginese
Buhid
CanadianAboriginal
Cherokee
+ Coptic
+ Cuneiform
+ Cypriot
Cyrillic
Deseret
Devanagari
Ethiopic
Georgian
+ Glagolitic
Gothic
Greek
Gujarati
Inherited
Kannada
Katakana
+ Kharoshthi
Khmer
Lao
Latin
+ Limbu
+ LinearB
Malayalam
Mongolian
Myanmar
+ NewTaiLue
+ Nko
Ogham
OldItalic
+ OldPersian
Oriya
+ Osmanya
+ PhagsPa
+ Phoenician
Runic
+ Shavian
Sinhala
+ SylotiNagri
Syriac
Tagalog
Tagbanwa
+ TaiLe
Tamil
Telugu
Thaana
Thai
Tibetan
+ Tifinagh
+ Ugaritic
Yi
+=item Extended property classes
+
Extended property classes can supplement the basic
properties, defined by the F<PropList> Unicode database:
Deprecated
Diacritic
Extender
- GraphemeLink
HexDigit
Hyphen
Ideographic
OtherAlphabetic
OtherDefaultIgnorableCodePoint
OtherGraphemeExtend
+ OtherIDStart
+ OtherIDContinue
OtherLowercase
OtherMath
OtherUppercase
+ PatternSyntax
+ PatternWhiteSpace
QuotationMark
Radical
SoftDotted
+ STerm
TerminalPunctuation
UnifiedIdeograph
+ VariationSelector
WhiteSpace
and there are further derived properties:
- Alphabetic Lu + Ll + Lt + Lm + Lo + OtherAlphabetic
- Lowercase Ll + OtherLowercase
- Uppercase Lu + OtherUppercase
- Math Sm + OtherMath
+ Alphabetic = Lu + Ll + Lt + Lm + Lo + Nl + OtherAlphabetic
+ Lowercase = Ll + OtherLowercase
+ Uppercase = Lu + OtherUppercase
+ Math = Sm + OtherMath
+
+ IDStart = Lu + Ll + Lt + Lm + Lo + Nl + OtherIDStart
+ IDContinue = IDStart + Mn + Mc + Nd + Pc + OtherIDContinue
+
+ DefaultIgnorableCodePoint
+ = OtherDefaultIgnorableCodePoint
+ + Cf + Cc + Cs + Noncharacters + VariationSelector
+ - WhiteSpace - FFF9..FFFB (Annotation Characters)
+
+ Any = Any code points (i.e. U+0000 to U+10FFFF)
+ Assigned = Any non-Cn code points (i.e. synonym for \P{Cn})
+ Unassigned = Synonym for \p{Cn}
+ ASCII = ASCII (i.e. U+0000 to U+007F)
- ID_Start Lu + Ll + Lt + Lm + Lo + Nl
- ID_Continue ID_Start + Mn + Mc + Nd + Pc
+ Common = Any character (or unassigned code point)
+ not explicitly assigned to a script
- Any Any character
- Assigned Any non-Cn character (i.e. synonym for \P{Cn})
- Unassigned Synonym for \p{Cn}
- Common Any character (or unassigned code point)
- not explicitly assigned to a script
+=item Use of "Is" Prefix
-For backward compatibility, all properties mentioned so far may have C<Is>
-prepended to their name, so C<\P{IsLu}>, for example, is equal to C<\P{Lu}>.
+For backward compatibility (with Perl 5.6), all properties mentioned
+so far may have C<Is> prepended to their name, so C<\P{IsLu}>, for
+example, is equal to C<\P{Lu}>.
-=head2 Blocks
+=item Blocks
-In addition to B<scripts>, Unicode also defines B<blocks> of characters.
-The difference between scripts and blocks is that the concept of
-scripts is closer to natural languages, while the concept of blocks
-is more of an artificial grouping based on groups of around 256
+In addition to B<scripts>, Unicode also defines B<blocks> of
+characters. The difference between scripts and blocks is that the
+concept of scripts is closer to natural languages, while the concept
+of blocks is more of an artificial grouping based on groups of 256
Unicode characters. For example, the C<Latin> script contains letters
-from many blocks but does not contain all the characters from those
+from many blocks but does not contain all the characters from those
blocks. It does not, for example, contain digits, because digits are
shared across many scripts. Digits and similar groups, like
punctuation, are in a category called C<Common>.
-For more about scripts, see the UTR #24:
+For more about scripts, see the UAX#24 "Script Names":
- http://www.unicode.org/unicode/reports/tr24/
+ http://www.unicode.org/reports/tr24/
For more about blocks, see:
Katakana block is referenced via C<\p{InKatakana}>. The C<In>
prefix may be omitted if there is no naming conflict with a script
or any other property, but it is recommended that C<In> always be used
-to avoid confusion.
+for block tests to avoid confusion.
These block names are supported:
+ InAegeanNumbers
InAlphabeticPresentationForms
+ InAncientGreekMusicalNotation
+ InAncientGreekNumbers
InArabic
InArabicPresentationFormsA
InArabicPresentationFormsB
+ InArabicSupplement
InArmenian
InArrows
+ InBalinese
InBasicLatin
InBengali
InBlockElements
InBopomofoExtended
InBoxDrawing
InBraillePatterns
+ InBuginese
InBuhid
InByzantineMusicalSymbols
InCJKCompatibility
InCJKCompatibilityIdeographs
InCJKCompatibilityIdeographsSupplement
InCJKRadicalsSupplement
+ InCJKStrokes
InCJKSymbolsAndPunctuation
InCJKUnifiedIdeographs
InCJKUnifiedIdeographsExtensionA
InCJKUnifiedIdeographsExtensionB
InCherokee
InCombiningDiacriticalMarks
+ InCombiningDiacriticalMarksSupplement
InCombiningDiacriticalMarksforSymbols
InCombiningHalfMarks
InControlPictures
+ InCoptic
+ InCountingRodNumerals
+ InCuneiform
+ InCuneiformNumbersAndPunctuation
InCurrencySymbols
+ InCypriotSyllabary
InCyrillic
- InCyrillicSupplementary
+ InCyrillicSupplement
InDeseret
InDevanagari
InDingbats
InEnclosedAlphanumerics
InEnclosedCJKLettersAndMonths
InEthiopic
+ InEthiopicExtended
+ InEthiopicSupplement
InGeneralPunctuation
InGeometricShapes
InGeorgian
+ InGeorgianSupplement
+ InGlagolitic
InGothic
InGreekExtended
InGreekAndCoptic
InKannada
InKatakana
InKatakanaPhoneticExtensions
+ InKharoshthi
InKhmer
+ InKhmerSymbols
InLao
InLatin1Supplement
InLatinExtendedA
InLatinExtendedAdditional
InLatinExtendedB
+ InLatinExtendedC
+ InLatinExtendedD
InLetterlikeSymbols
+ InLimbu
+ InLinearBIdeograms
+ InLinearBSyllabary
InLowSurrogates
InMalayalam
InMathematicalAlphanumericSymbols
InMiscellaneousMathematicalSymbolsA
InMiscellaneousMathematicalSymbolsB
InMiscellaneousSymbols
+ InMiscellaneousSymbolsAndArrows
InMiscellaneousTechnical
+ InModifierToneLetters
InMongolian
InMusicalSymbols
InMyanmar
+ InNKo
+ InNewTaiLue
InNumberForms
InOgham
InOldItalic
+ InOldPersian
InOpticalCharacterRecognition
InOriya
+ InOsmanya
+ InPhagspa
+ InPhoenician
+ InPhoneticExtensions
+ InPhoneticExtensionsSupplement
InPrivateUseArea
InRunic
+ InShavian
InSinhala
InSmallFormVariants
InSpacingModifierLetters
InSupplementalArrowsA
InSupplementalArrowsB
InSupplementalMathematicalOperators
+ InSupplementalPunctuation
InSupplementaryPrivateUseAreaA
InSupplementaryPrivateUseAreaB
+ InSylotiNagri
InSyriac
InTagalog
InTagbanwa
InTags
+ InTaiLe
+ InTaiXuanJingSymbols
InTamil
InTelugu
InThaana
InThai
InTibetan
+ InTifinagh
+ InUgaritic
InUnifiedCanadianAboriginalSyllabics
InVariationSelectors
+ InVariationSelectorsSupplement
+ InVerticalForms
InYiRadicals
InYiSyllables
-
-=over 4
-
-=item *
-
-The special pattern C<\X> matches any extended Unicode
-sequence--"a combining character sequence" in Standardese--where the
-first character is a base character and subsequent characters are mark
-characters that apply to the base character. C<\X> is equivalent to
-C<(?:\PM\pM*)>.
-
-=item *
-
-The C<tr///> operator translates characters instead of bytes. Note
-that the C<tr///CU> functionality has been removed. For similar
-functionality see pack('U0', ...) and pack('C0', ...).
-
-=item *
-
-Case translation operators use the Unicode case translation tables
-when character input is provided. Note that C<uc()>, or C<\U> in
-interpolated strings, translates to uppercase, while C<ucfirst>,
-or C<\u> in interpolated strings, translates to titlecase in languages
-that make the distinction.
-
-=item *
-
-Most operators that deal with positions or lengths in a string will
-automatically switch to using character positions, including
-C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>,
-C<sprintf()>, C<write()>, and C<length()>. Operators that
-specifically do not switch include C<vec()>, C<pack()>, and
-C<unpack()>. Operators that really don't care include C<chomp()>,
-operators that treats strings as a bucket of bits such as C<sort()>,
-and operators dealing with filenames.
-
-=item *
-
-The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change,
-since they are often used for byte-oriented formats. Again, think
-"C<char>" in the C language. There is a new "C<U>" specifier
-that converts between Unicode characters and integers.
-
-=item *
-
-The C<chr()> and C<ord()> functions work on characters, similar to
-C<pack("U")> and C<unpack("U")>, I<not> C<pack("C")> and
-C<unpack("C")>. C<pack("C")> and C<unpack("C")> are methods for
-emulating byte-oriented C<chr()> and C<ord()> on Unicode strings.
-While these methods reveal the internal encoding of Unicode strings,
-that is not something one normally needs to care about at all.
-
-=item *
-
-The bit string operators, C<& | ^ ~>, can operate on character data.
-However, for backward compatibility, such as when using bit string
-operations when characters are all less than 256 in ordinal value, one
-should not use C<~> (the bit complement) with characters of both
-values less than 256 and values greater than 256. Most importantly,
-DeMorgan's laws (C<~($x|$y) eq ~$x&~$y> and C<~($x&$y) eq ~$x|~$y>)
-will not hold. The reason for this mathematical I<faux pas> is that
-the complement cannot return B<both> the 8-bit (byte-wide) bit
-complement B<and> the full character-wide bit complement.
-
-=item *
-
-lc(), uc(), lcfirst(), and ucfirst() work for the following cases:
-
-=over 8
-
-=item *
-
-the case mapping is from a single Unicode character to another
-single Unicode character, or
-
-=item *
-
-the case mapping is from a single Unicode character to more
-than one Unicode character.
+ InYijingHexagramSymbols
=back
-The following cases do not yet work:
-
-=over 8
-
-=item *
-
-the "final sigma" (Greek), and
-
-=item *
-
-anything to with locales (Lithuanian, Turkish, Azeri).
-
-=back
-
-See the Unicode Technical Report #21, Case Mappings, for more details.
+=head2 User-Defined Character Properties
-=item *
+You can define your own character properties by defining subroutines
+whose names begin with "In" or "Is". The subroutines can be defined in
+any package. The user-defined properties can be used in the regular
+expression C<\p> and C<\P> constructs; if you are using a user-defined
+property from a package other than the one you are in, you must specify
+its package in the C<\p> or C<\P> construct.
-And finally, C<scalar reverse()> reverses by character rather than by byte.
+ # assuming property IsForeign defined in Lang::
+ package main; # property package name required
+ if ($txt =~ /\p{Lang::IsForeign}+/) { ... }
-=back
+ package Lang; # property package name not required
+ if ($txt =~ /\p{IsForeign}+/) { ... }
-=head2 User-Defined Character Properties
-You can define your own character properties by defining subroutines
-whose names begin 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.
+Note that the effect is compile-time and immutable once defined.
The subroutines must return a specially-formatted string, with one
or more newline-separated lines. Each line must be one of the following:
=item *
Something to include, prefixed by "+": a built-in character
-property (prefixed by "utf8::"), to represent all the characters in that
-property; two hexadecimal code points for a range; or a single
-hexadecimal code point.
+property (prefixed by "utf8::") or a user-defined character property,
+to represent all the characters in that property; two hexadecimal code
+points for a range; or a single hexadecimal code point.
=item *
Something to exclude, prefixed by "-": an existing character
-property (prefixed by "utf8::"), for all the characters in that
-property; two hexadecimal code points for a range; or a single
-hexadecimal code point.
+property (prefixed by "utf8::") or a user-defined character property,
+to represent all the characters in that property; two hexadecimal code
+points for a range; or a single hexadecimal code point.
=item *
Something to negate, prefixed "!": an existing character
-property (prefixed by "utf8::") for all the characters except the
-characters in the property; two hexadecimal code points for a range;
-or a single hexadecimal code point.
+property (prefixed by "utf8::") or a user-defined character property,
+to represent all the characters in that property; two hexadecimal code
+points for a range; or a single hexadecimal code point.
+
+=item *
+
+Something to intersect with, prefixed by "&": an existing character
+property (prefixed by "utf8::") or a user-defined character property,
+for all the characters except the characters in the property; two
+hexadecimal code points for a range; or a single hexadecimal code point.
=back
END
}
+Intersection is useful for getting the common characters matched by
+two (or more) classes.
+
+ sub InFooAndBar {
+ return <<'END';
+ +main::Foo
+ &main::Bar
+ END
+ }
+
+It's important to remember not to use "&" for the first set -- that
+would be intersecting with nothing (resulting in an empty set).
+
+A final note on the user-defined property tests: they will be used
+only if the scalar has been marked as having Unicode characters.
+Old byte-style strings will not be affected.
+
+=head2 User-Defined Case Mappings
+
+You can also define your own mappings to be used in the lc(),
+lcfirst(), uc(), and ucfirst() (or their string-inlined versions).
+The principle is similar to that of user-defined character
+properties: to define subroutines in the C<main> package
+with names like C<ToLower> (for lc() and lcfirst()), C<ToTitle> (for
+the first character in ucfirst()), and C<ToUpper> (for uc(), and the
+rest of the characters in ucfirst()).
+
+The string returned by the subroutines needs now to be three
+hexadecimal numbers separated by tabulators: start of the source
+range, end of the source range, and start of the destination range.
+For example:
+
+ sub ToUpper {
+ return <<END;
+ 0061\t0063\t0041
+ END
+ }
+
+defines an uc() mapping that causes only the characters "a", "b", and
+"c" to be mapped to "A", "B", "C", all other characters will remain
+unchanged.
+
+If there is no source range to speak of, that is, the mapping is from
+a single character to another single character, leave the end of the
+source range empty, but the two tabulator characters are still needed.
+For example:
+
+ sub ToLower {
+ return <<END;
+ 0041\t\t0061
+ END
+ }
+
+defines a lc() mapping that causes only "A" to be mapped to "a", all
+other characters will remain unchanged.
+
+(For serious hackers only) If you want to introspect the default
+mappings, you can find the data in the directory
+C<$Config{privlib}>/F<unicore/To/>. The mapping data is returned as
+the here-document, and the C<utf8::ToSpecFoo> are special exception
+mappings derived from <$Config{privlib}>/F<unicore/SpecialCasing.txt>.
+The C<Digit> and C<Fold> mappings that one can see in the directory
+are not directly user-accessible, one can use either the
+C<Unicode::UCD> module, or just match case-insensitively (that's when
+the C<Fold> mapping is used).
+
+A final note on the user-defined case mappings: they will be used
+only if the scalar has been marked as having Unicode characters.
+Old byte-style strings will not be affected.
+
=head2 Character Encodings for Input and Output
See L<Encode>.
The following list of Unicode support for regular expressions describes
all the features currently supported. The references to "Level N"
-and the section numbers refer to the Unicode Technical Report 18,
-"Unicode Regular Expression Guidelines".
+and the section numbers refer to the Unicode Technical Standard #18,
+"Unicode Regular Expressions", version 11, in May 2005.
=over 4
Level 1 - Basic Unicode Support
- 2.1 Hex Notation - done [1]
- Named Notation - done [2]
- 2.2 Categories - done [3][4]
- 2.3 Subtraction - MISSING [5][6]
- 2.4 Simple Word Boundaries - done [7]
- 2.5 Simple Loose Matches - done [8]
- 2.6 End of Line - MISSING [9][10]
-
- [ 1] \x{...}
- [ 2] \N{...}
- [ 3] . \p{...} \P{...}
- [ 4] now scripts (see UTR#24 Script Names) in addition to blocks
- [ 5] have negation
- [ 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 case-folding in matching, not Simple:
- for example U+1F88 is equivalent with U+1F000 U+03B9,
+ RL1.1 Hex Notation - done [1]
+ RL1.2 Properties - done [2][3]
+ RL1.2a Compatibility Properties - done [4]
+ RL1.3 Subtraction and Intersection - MISSING [5]
+ RL1.4 Simple Word Boundaries - done [6]
+ RL1.5 Simple Loose Matches - done [7]
+ RL1.6 Line Boundaries - MISSING [8]
+ RL1.7 Supplementary Code Points - done [9]
+
+ [1] \x{...}
+ [2] \p{...} \P{...}
+ [3] supports not only minimal list (general category, scripts,
+ Alphabetic, Lowercase, Uppercase, WhiteSpace,
+ NoncharacterCodePoint, DefaultIgnorableCodePoint, Any,
+ ASCII, Assigned), but also bidirectional types, blocks, etc.
+ (see L</"Unicode Character Properties">)
+ [4] \d \D \s \S \w \W \X [:prop:] [:^prop:]
+ [5] can use regular expression look-ahead [a] or
+ user-defined character properties [b] to emulate set operations
+ [6] \b \B
+ [7] note that Perl does Full case-folding in matching, not Simple:
+ for example U+1F88 is equivalent with U+1F00 U+03B9,
not with 1F80. This difference matters for certain Greek
capital letters with certain modifiers: the Full case-folding
decomposes the letter, while the Simple case-folding would map
it to a single character.
- [ 9] see UTR#13 Unicode Newline Guidelines
- [10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029})
- (should also affect <>, $., and script line numbers)
- (the \x{85}, \x{2028} and \x{2029} do match \s)
+ [8] should do ^ and $ also on U+000B (\v in C), FF (\f), CR (\r),
+ CRLF (\r\n), NEL (U+0085), LS (U+2028), and PS (U+2029);
+ should also affect <>, $., and script line numbers;
+ should not split lines within CRLF [c] (i.e. there is no empty
+ line between \r and \n)
+ [9] UTF-8/UTF-EBDDIC used in perl allows not only U+10000 to U+10FFFF
+ but also beyond U+10FFFF [d]
[a] You can mimic class subtraction using lookahead.
-For example, what TR18 might write as
+For example, what UTS#18 might write as
[{Greek}-[{UNASSIGNED}]]
But in this particular example, you probably really want
- \p{Greek}
+ \p{GreekAndCoptic}
which will match assigned characters known to be part of the Greek script.
-[b] See L</User-defined Character Properties>.
+Also see the Unicode::Regex::Set module, it does implement the full
+UTS#18 grouping, intersection, union, and removal (subtraction) syntax.
-=item *
+[b] '+' for union, '-' for removal (set-difference), '&' for intersection
+(see L</"User-Defined Character Properties">)
-Level 2 - Extended Unicode Support
+[c] Try the C<:crlf> layer (see L<PerlIO>).
- 3.1 Surrogates - MISSING
- 3.2 Canonical Equivalents - MISSING [11][12]
- 3.3 Locale-Independent Graphemes - MISSING [13]
- 3.4 Locale-Independent Words - MISSING [14]
- 3.5 Locale-Independent Loose Matches - MISSING [15]
-
- [11] see UTR#15 Unicode Normalization
- [12] have Unicode::Normalize but not integrated to regexes
- [13] have \X but at this level . should equal that
- [14] need three classes, not just \w and \W
- [15] see UTR#21 Case Mappings
+[d] Avoid C<use warning 'utf8';> (or say C<no warning 'utf8';>) to allow
+U+FFFF (C<\x{FFFF}>).
=item *
-Level 3 - Locale-Sensitive Support
+Level 2 - Extended Unicode Support
+
+ RL2.1 Canonical Equivalents - MISSING [10][11]
+ RL2.2 Default Grapheme Clusters - MISSING [12][13]
+ RL2.3 Default Word Boundaries - MISSING [14]
+ RL2.4 Default Loose Matches - MISSING [15]
+ RL2.5 Name Properties - MISSING [16]
+ RL2.6 Wildcard Properties - MISSING
+
+ [10] see UAX#15 "Unicode Normalization Forms"
+ [11] have Unicode::Normalize but not integrated to regexes
+ [12] have \X but at this level . should equal that
+ [13] UAX#29 "Text Boundaries" considers CRLF and Hangul syllable
+ clusters as a single grapheme cluster.
+ [14] see UAX#29, Word Boundaries
+ [15] see UAX#21 "Case Mappings"
+ [16] have \N{...} but neither compute names of CJK Ideographs
+ and Hangul Syllables nor use a loose match [e]
+
+[e] C<\N{...}> allows namespaces (see L<charnames>).
- 4.1 Locale-Dependent Categories - MISSING
- 4.2 Locale-Dependent Graphemes - MISSING [16][17]
- 4.3 Locale-Dependent Words - MISSING
- 4.4 Locale-Dependent Loose Matches - MISSING
- 4.5 Locale-Dependent Ranges - MISSING
+=item *
- [16] see UTR#10 Unicode Collation Algorithms
- [17] have Unicode::Collate but not integrated to regexes
+Level 3 - Tailored Support
+
+ RL3.1 Tailored Punctuation - MISSING
+ RL3.2 Tailored Grapheme Clusters - MISSING [17][18]
+ RL3.3 Tailored Word Boundaries - MISSING
+ RL3.4 Tailored Loose Matches - MISSING
+ RL3.5 Tailored Ranges - MISSING
+ RL3.6 Context Matching - MISSING [19]
+ RL3.7 Incremental Matches - MISSING
+ ( RL3.8 Unicode Set Sharing )
+ RL3.9 Possible Match Sets - MISSING
+ RL3.10 Folded Matching - MISSING [20]
+ RL3.11 Submatchers - MISSING
+
+ [17] see UAX#10 "Unicode Collation Algorithms"
+ [18] have Unicode::Collate but not integrated to regexes
+ [19] have (?<=x) and (?=x), but look-aheads or look-behinds should see
+ outside of the target substring
+ [20] need insensitive matching for linguistic features other than case;
+ for example, hiragana to katakana, wide and narrow, simplified Han
+ to traditional Han (see UTR#30 "Character Foldings")
=back
=item *
-UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks)
+UTF-16, UTF-16BE, UTF-16LE, Surrogates, and BOMs (Byte Order Marks)
-The followings items are mostly for reference, Perl doesn't
-use them internally.
+The followings items are mostly for reference and general Unicode
+knowledge, Perl doesn't use these constructs internally.
UTF-16 is a 2 or 4 byte encoding. The Unicode code points
-C<U+0000..U+FFFF> are stored in a single 16-bit unit, and the code points
-C<U+10000..U+10FFFF> in two 16-bit units. The latter case is
+C<U+0000..U+FFFF> are stored in a single 16-bit unit, and the code
+points C<U+10000..U+10FFFF> in two 16-bit units. The latter case is
using I<surrogates>, the first 16-bit unit being the I<high
surrogate>, and the second being the I<low surrogate>.
The way this trick works is that the character with the code point
C<U+FFFE> is guaranteed not to be a valid Unicode character, so the
sequence of bytes C<0xFF 0xFE> is unambiguously "BOM, represented in
-little-endian format" and cannot be "C<U+FFFE>, represented in big-endian
+little-endian format" and cannot be C<U+FFFE>, represented in big-endian
format".
=item *
-UTF-32, UTF-32BE, UTF32-LE
+UTF-32, UTF-32BE, UTF-32LE
The UTF-32 family is pretty much like the UTF-16 family, expect that
the units are 32-bit, and therefore the surrogate scheme is not
more letters according to your language and country.
In the second case, the C<\w> set of characters is much, much larger.
-Most importantly, even in the set of the first 256 characters, it
-will probably match different characters: unlike most locales,
-which are specific to a language and country pair, Unicode classifies all
-the characters that are letters as C<\w>. For example, your locale might
-not think that LATIN SMALL LETTER ETH is a letter (unless you happen
-to speak Icelandic), but Unicode does.
+Most importantly, even in the set of the first 256 characters, it will
+probably match different characters: unlike most locales, which are
+specific to a language and country pair, Unicode classifies all the
+characters that are letters I<somewhere> as C<\w>. For example, your
+locale might not think that LATIN SMALL LETTER ETH is a letter (unless
+you happen to speak Icelandic), but Unicode does.
As discussed elsewhere, Perl has one foot (two hooves?) planted in
-each of two worlds: the old world of bytes and the new
-world of characters, upgrading from bytes to characters when necessary.
+each of two worlds: the old world of bytes and the new world of
+characters, upgrading from bytes to characters when necessary.
If your legacy code does not explicitly use Unicode, no automatic
switch-over to characters should happen. Characters shouldn't get
-downgraded to bytes, either. It is possible to accidentally mix
-bytes and characters, however (see L<perluniintro>), in which case
-C<\w> in regular expressions might start behaving differently. Review
-your code.
+downgraded to bytes, either. It is possible to accidentally mix bytes
+and characters, however (see L<perluniintro>), in which case C<\w> in
+regular expressions might start behaving differently. Review your
+code. Use warnings and the C<strict> pragma.
=back
=item *
-If your locale environment variables (LANGUAGE, LC_ALL, LC_CTYPE, LANG)
-contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching),
-the default encodings of your STDIN, STDOUT, and STDERR, and of
-B<any subsequent file open>, are considered to be UTF-8.
+You can enable automatic UTF-8-ification of your standard file
+handles, default C<open()> layer, and C<@ARGV> by using either
+the C<-C> command line switch or the C<PERL_UNICODE> environment
+variable, see L<perlrun> for the documentation of the C<-C> switch.
=item *
=back
+=head2 When Unicode Does Not Happen
+
+While Perl does have extensive ways to input and output in Unicode,
+and few other 'entry points' like the @ARGV which can be interpreted
+as Unicode (UTF-8), there still are many places where Unicode (in some
+encoding or another) could be given as arguments or received as
+results, or both, but it is not.
+
+The following are such interfaces. For all of these interfaces Perl
+currently (as of 5.8.3) simply assumes byte strings both as arguments
+and results, or UTF-8 strings if the C<encoding> pragma has been used.
+
+One reason why Perl does not attempt to resolve the role of Unicode in
+this cases is that the answers are highly dependent on the operating
+system and the file system(s). For example, whether filenames can be
+in Unicode, and in exactly what kind of encoding, is not exactly a
+portable concept. Similarly for the qx and system: how well will the
+'command line interface' (and which of them?) handle Unicode?
+
+=over 4
+
+=item *
+
+chdir, chmod, chown, chroot, exec, link, lstat, mkdir,
+rename, rmdir, stat, symlink, truncate, unlink, utime, -X
+
+=item *
+
+%ENV
+
+=item *
+
+glob (aka the <*>)
+
+=item *
+
+open, opendir, sysopen
+
+=item *
+
+qx (aka the backtick operator), system
+
+=item *
+
+readdir, readlink
+
+=back
+
+=head2 Forcing Unicode in Perl (Or Unforcing Unicode in Perl)
+
+Sometimes (see L</"When Unicode Does Not Happen">) there are
+situations where you simply need to force Perl to believe that a byte
+string is UTF-8, or vice versa. The low-level calls
+utf8::upgrade($bytestring) and utf8::downgrade($utf8string) are
+the answers.
+
+Do not use them without careful thought, though: Perl may easily get
+very confused, angry, or even crash, if you suddenly change the 'nature'
+of scalar like that. Especially careful you have to be if you use the
+utf8::upgrade(): any random byte string is not valid UTF-8.
+
=head2 Using Unicode in XS
-If you want to handle Perl Unicode in XS extensions, you may find
-the following C APIs useful. See L<perlapi> for details.
+If you want to handle Perl Unicode in XS extensions, you may find the
+following C APIs useful. See also L<perlguts/"Unicode Support"> for an
+explanation about Unicode at the XS level, and L<perlapi> for the API
+details.
=over 4
=item *
-C<DO_UTF8(sv)> returns true if the C<UTF8> flag is on and the bytes pragma
-is not in effect. C<SvUTF8(sv)> returns true is the C<UTF8> flag is on; the
-bytes pragma is ignored. The C<UTF8> flag being on does B<not> mean that
-there are any characters of code points greater than 255 (or 127) in
-the scalar or that there are even any characters in the scalar.
-What the C<UTF8> flag means is that the sequence of octets in the
-representation of the scalar is the sequence of UTF-8 encoded
-code points of the characters of a string. The C<UTF8> flag being
-off means that each octet in this representation encodes a single
-character with code point 0..255 within the string. Perl's Unicode
-model is not to use UTF-8 until it is absolutely necessary.
+C<DO_UTF8(sv)> returns true if the C<UTF8> flag is on and the bytes
+pragma is not in effect. C<SvUTF8(sv)> returns true is the C<UTF8>
+flag is on; the bytes pragma is ignored. The C<UTF8> flag being on
+does B<not> mean that there are any characters of code points greater
+than 255 (or 127) in the scalar or that there are even any characters
+in the scalar. What the C<UTF8> flag means is that the sequence of
+octets in the representation of the scalar is the sequence of UTF-8
+encoded code points of the characters of a string. The C<UTF8> flag
+being off means that each octet in this representation encodes a
+single character with code point 0..255 within the string. Perl's
+Unicode model is not to use UTF-8 until it is absolutely necessary.
=item *
-C<uvuni_to_utf8(buf, chr>) writes a Unicode character code point into a
-buffer encoding the code point as UTF-8, and returns a pointer
+C<uvuni_to_utf8(buf, chr)> writes a Unicode character code point into
+a buffer encoding the code point as UTF-8, and returns a pointer
pointing after the UTF-8 bytes.
=item *
C<sv_uni_display(dsv, ssv, pvlim, flags)> are useful for debugging the
output of Unicode strings and scalars. By default they are useful
only for debugging--they display B<all> characters as hexadecimal code
-points--but with the flags C<UNI_DISPLAY_ISPRINT> and
-C<UNI_DISPLAY_BACKSLASH> you can make the output more readable.
+points--but with the flags C<UNI_DISPLAY_ISPRINT>,
+C<UNI_DISPLAY_BACKSLASH>, and C<UNI_DISPLAY_QQ> you can make the
+output more readable.
=item *
=head2 Interaction with Extensions
When Perl exchanges data with an extension, the extension should be
-able to understand the UTF-8 flag and act accordingly. If the
+able to understand the UTF8 flag and act accordingly. If the
extension doesn't know about the flag, it's likely that the extension
will return incorrectly-flagged data.
Some functions are slower when working on UTF-8 encoded strings than
on byte encoded strings. All functions that need to hop over
-characters such as length(), substr() or index() can work B<much>
-faster when the underlying data are byte-encoded. Witness the
-following benchmark:
-
- % perl -e '
- use Benchmark;
- use strict;
- our $l = 10000;
- our $u = our $b = "x" x $l;
- substr($u,0,1) = "\x{100}";
- timethese(-2,{
- LENGTH_B => q{ length($b) },
- LENGTH_U => q{ length($u) },
- SUBSTR_B => q{ substr($b, $l/4, $l/2) },
- SUBSTR_U => q{ substr($u, $l/4, $l/2) },
- });
- '
- Benchmark: running LENGTH_B, LENGTH_U, SUBSTR_B, SUBSTR_U for at least 2 CPU seconds...
- LENGTH_B: 2 wallclock secs ( 2.36 usr + 0.00 sys = 2.36 CPU) @ 5649983.05/s (n=13333960)
- LENGTH_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 12155.45/s (n=25648)
- SUBSTR_B: 3 wallclock secs ( 2.16 usr + 0.00 sys = 2.16 CPU) @ 374480.09/s (n=808877)
- SUBSTR_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 6791.00/s (n=14329)
-
-The numbers show an incredible slowness on long UTF-8 strings. You
-should carefully avoid using these functions in tight loops. If you
-want to iterate over characters, the superior coding technique would
-split the characters into an array instead of using substr, as the following
-benchmark shows:
-
- % perl -e '
- use Benchmark;
- use strict;
- our $l = 10000;
- our $u = our $b = "x" x $l;
- substr($u,0,1) = "\x{100}";
- timethese(-5,{
- SPLIT_B => q{ for my $c (split //, $b){} },
- SPLIT_U => q{ for my $c (split //, $u){} },
- SUBSTR_B => q{ for my $i (0..length($b)-1){my $c = substr($b,$i,1);} },
- SUBSTR_U => q{ for my $i (0..length($u)-1){my $c = substr($u,$i,1);} },
- });
- '
- Benchmark: running SPLIT_B, SPLIT_U, SUBSTR_B, SUBSTR_U for at least 5 CPU seconds...
- SPLIT_B: 6 wallclock secs ( 5.29 usr + 0.00 sys = 5.29 CPU) @ 56.14/s (n=297)
- SPLIT_U: 5 wallclock secs ( 5.17 usr + 0.01 sys = 5.18 CPU) @ 55.21/s (n=286)
- SUBSTR_B: 5 wallclock secs ( 5.34 usr + 0.00 sys = 5.34 CPU) @ 123.22/s (n=658)
- SUBSTR_U: 7 wallclock secs ( 6.20 usr + 0.00 sys = 6.20 CPU) @ 0.81/s (n=5)
-
-Even though the algorithm based on C<substr()> is faster than
-C<split()> for byte-encoded data, it pales in comparison to the speed
-of C<split()> when used with UTF-8 data.
+characters such as length(), substr() or index(), or matching regular
+expressions can work B<much> faster when the underlying data are
+byte-encoded.
+
+In Perl 5.8.0 the slowness was often quite spectacular; in Perl 5.8.1
+a caching scheme was introduced which will hopefully make the slowness
+somewhat less spectacular, at least for some operations. In general,
+operations with UTF-8 encoded strings are still slower. As an example,
+the Unicode properties (character classes) like C<\p{Nd}> are known to
+be quite a bit slower (5-20 times) than their simpler counterparts
+like C<\d> (then again, there 268 Unicode characters matching C<Nd>
+compared with the 10 ASCII characters matching C<d>).
+
+=head2 Porting code from perl-5.6.X
+
+Perl 5.8 has a different Unicode model from 5.6. In 5.6 the programmer
+was required to use the C<utf8> pragma to declare that a given scope
+expected to deal with Unicode data and had to make sure that only
+Unicode data were reaching that scope. If you have code that is
+working with 5.6, you will need some of the following adjustments to
+your code. The examples are written such that the code will continue
+to work under 5.6, so you should be safe to try them out.
+
+=over 4
+
+=item *
+
+A filehandle that should read or write UTF-8
+
+ if ($] > 5.007) {
+ binmode $fh, ":utf8";
+ }
+
+=item *
+
+A scalar that is going to be passed to some extension
+
+Be it Compress::Zlib, Apache::Request or any extension that has no
+mention of Unicode in the manpage, you need to make sure that the
+UTF8 flag is stripped off. Note that at the time of this writing
+(October 2002) the mentioned modules are not UTF-8-aware. Please
+check the documentation to verify if this is still true.
+
+ if ($] > 5.007) {
+ require Encode;
+ $val = Encode::encode_utf8($val); # make octets
+ }
+
+=item *
+
+A scalar we got back from an extension
+
+If you believe the scalar comes back as UTF-8, you will most likely
+want the UTF8 flag restored:
+
+ if ($] > 5.007) {
+ require Encode;
+ $val = Encode::decode_utf8($val);
+ }
+
+=item *
+
+Same thing, if you are really sure it is UTF-8
+
+ if ($] > 5.007) {
+ require Encode;
+ Encode::_utf8_on($val);
+ }
+
+=item *
+
+A wrapper for fetchrow_array and fetchrow_hashref
+
+When the database contains only UTF-8, a wrapper function or method is
+a convenient way to replace all your fetchrow_array and
+fetchrow_hashref calls. A wrapper function will also make it easier to
+adapt to future enhancements in your database driver. Note that at the
+time of this writing (October 2002), the DBI has no standardized way
+to deal with UTF-8 data. Please check the documentation to verify if
+that is still true.
+
+ sub fetchrow {
+ my($self, $sth, $what) = @_; # $what is one of fetchrow_{array,hashref}
+ if ($] < 5.007) {
+ return $sth->$what;
+ } else {
+ require Encode;
+ if (wantarray) {
+ my @arr = $sth->$what;
+ for (@arr) {
+ defined && /[^\000-\177]/ && Encode::_utf8_on($_);
+ }
+ return @arr;
+ } else {
+ my $ret = $sth->$what;
+ if (ref $ret) {
+ for my $k (keys %$ret) {
+ defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret->{$k};
+ }
+ return $ret;
+ } else {
+ defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret;
+ return $ret;
+ }
+ }
+ }
+ }
+
+
+=item *
+
+A large scalar that you know can only contain ASCII
+
+Scalars that contain only ASCII and are marked as UTF-8 are sometimes
+a drag to your program. If you recognize such a situation, just remove
+the UTF8 flag:
+
+ utf8::downgrade($val) if $] > 5.007;
+
+=back
=head1 SEE ALSO
-L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>,
-L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}">
+L<perlunitut>, L<perluniintro>, L<Encode>, L<open>, L<utf8>, L<bytes>,
+L<perlretut>, L<perlvar/"${^UNICODE}">
=cut
projects / p5sagit/p5-mst-13.2.git / blobdiff