Commit | Line | Data |
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393fec97 GS |
1 | =head1 NAME |
2 | ||
3 | perlunicode - Unicode support in Perl | |
4 | ||
5 | =head1 DESCRIPTION | |
6 | ||
0a1f2d14 | 7 | =head2 Important Caveats |
21bad921 | 8 | |
0a1f2d14 NIS |
9 | WARNING: While the implementation of Unicode support in Perl is now fairly |
10 | complete it is still evolving to some extent. | |
21bad921 | 11 | |
75daf61c JH |
12 | In particular the way Unicode is handled on EBCDIC platforms is still |
13 | rather experimental. On such a platform references to UTF-8 encoding | |
14 | in this document and elsewhere should be read as meaning UTF-EBCDIC as | |
15 | specified in Unicode Technical Report 16 unless ASCII vs EBCDIC issues | |
16 | are specifically discussed. There is no C<utfebcdic> pragma or | |
17 | ":utfebcdic" layer, rather "utf8" and ":utf8" are re-used to mean | |
18 | platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> for | |
19 | more discussion of the issues. | |
0a1f2d14 NIS |
20 | |
21 | The following areas are still under development. | |
21bad921 | 22 | |
13a2d996 | 23 | =over 4 |
21bad921 GS |
24 | |
25 | =item Input and Output Disciplines | |
26 | ||
75daf61c JH |
27 | A filehandle can be marked as containing perl's internal Unicode |
28 | encoding (UTF-8 or UTF-EBCDIC) by opening it with the ":utf8" layer. | |
0a1f2d14 | 29 | Other encodings can be converted to perl's encoding on input, or from |
75daf61c JH |
30 | perl's encoding on output by use of the ":encoding()" layer. There is |
31 | not yet a clean way to mark the Perl source itself as being in an | |
32 | particular encoding. | |
21bad921 GS |
33 | |
34 | =item Regular Expressions | |
35 | ||
e6739005 JH |
36 | The regular expression compiler does now attempt to produce |
37 | polymorphic opcodes. That is the pattern should now adapt to the data | |
75daf61c JH |
38 | and automatically switch to the Unicode character scheme when |
39 | presented with Unicode data, or a traditional byte scheme when | |
40 | presented with byte data. The implementation is still new and | |
41 | (particularly on EBCDIC platforms) may need further work. | |
21bad921 | 42 | |
ad0029c4 | 43 | =item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts |
21bad921 | 44 | |
75daf61c JH |
45 | The C<utf8> pragma implements the tables used for Unicode support. |
46 | These tables are automatically loaded on demand, so the C<utf8> pragma | |
47 | need not normally be used. | |
21bad921 | 48 | |
75daf61c | 49 | However, as a compatibility measure, this pragma must be explicitly |
ad0029c4 JH |
50 | used to enable recognition of UTF-8 in the Perl scripts themselves on |
51 | ASCII based machines or recognize UTF-EBCDIC on EBCDIC based machines. | |
7dedd01f JH |
52 | B<NOTE: this should be the only place where an explicit C<use utf8> is |
53 | needed>. | |
21bad921 GS |
54 | |
55 | =back | |
56 | ||
57 | =head2 Byte and Character semantics | |
393fec97 GS |
58 | |
59 | Beginning with version 5.6, Perl uses logically wide characters to | |
60 | represent strings internally. This internal representation of strings | |
b3419ed8 | 61 | uses either the UTF-8 or the UTF-EBCDIC encoding. |
393fec97 | 62 | |
75daf61c JH |
63 | In future, Perl-level operations can be expected to work with |
64 | characters rather than bytes, in general. | |
393fec97 | 65 | |
75daf61c JH |
66 | However, as strictly an interim compatibility measure, Perl aims to |
67 | provide a safe migration path from byte semantics to character | |
68 | semantics for programs. For operations where Perl can unambiguously | |
69 | decide that the input data is characters, Perl now switches to | |
70 | character semantics. For operations where this determination cannot | |
71 | be made without additional information from the user, Perl decides in | |
72 | favor of compatibility, and chooses to use byte semantics. | |
8cbd9a7a GS |
73 | |
74 | This behavior preserves compatibility with earlier versions of Perl, | |
75 | which allowed byte semantics in Perl operations, but only as long as | |
76 | none of the program's inputs are marked as being as source of Unicode | |
77 | character data. Such data may come from filehandles, from calls to | |
78 | external programs, from information provided by the system (such as %ENV), | |
21bad921 | 79 | or from literals and constants in the source text. |
8cbd9a7a | 80 | |
75daf61c JH |
81 | If the C<-C> command line switch is used, (or the |
82 | ${^WIDE_SYSTEM_CALLS} global flag is set to C<1>), all system calls | |
83 | will use the corresponding wide character APIs. Note that this is | |
84 | currently only implemented on Windows since other platforms API | |
85 | standard on this area. | |
8cbd9a7a | 86 | |
75daf61c JH |
87 | Regardless of the above, the C<bytes> pragma can always be used to |
88 | force byte semantics in a particular lexical scope. See L<bytes>. | |
8cbd9a7a GS |
89 | |
90 | The C<utf8> pragma is primarily a compatibility device that enables | |
75daf61c | 91 | recognition of UTF-(8|EBCDIC) in literals encountered by the parser. |
7dedd01f JH |
92 | Note that this pragma is only required until a future version of Perl |
93 | in which character semantics will become the default. This pragma may | |
94 | then become a no-op. See L<utf8>. | |
8cbd9a7a GS |
95 | |
96 | Unless mentioned otherwise, Perl operators will use character semantics | |
97 | when they are dealing with Unicode data, and byte semantics otherwise. | |
98 | Thus, character semantics for these operations apply transparently; if | |
99 | the input data came from a Unicode source (for example, by adding a | |
100 | character encoding discipline to the filehandle whence it came, or a | |
101 | literal UTF-8 string constant in the program), character semantics | |
102 | apply; otherwise, byte semantics are in effect. To force byte semantics | |
8058d7ab | 103 | on Unicode data, the C<bytes> pragma should be used. |
393fec97 | 104 | |
7dedd01f JH |
105 | Notice that if you have a string with byte semantics and you then |
106 | add character data into it, the bytes will be upgraded I<as if they | |
107 | were ISO 8859-1 (Latin-1)> (or if in EBCDIC, after a translation | |
108 | to ISO 8859-1). | |
109 | ||
393fec97 | 110 | Under character semantics, many operations that formerly operated on |
75daf61c JH |
111 | bytes change to operating on characters. For ASCII data this makes no |
112 | difference, because UTF-8 stores ASCII in single bytes, but for any | |
113 | character greater than C<chr(127)>, the character B<may> be stored in | |
393fec97 | 114 | a sequence of two or more bytes, all of which have the high bit set. |
2796c109 JH |
115 | |
116 | For C1 controls or Latin 1 characters on an EBCDIC platform the | |
117 | character may be stored in a UTF-EBCDIC multi byte sequence. But by | |
118 | and large, the user need not worry about this, because Perl hides it | |
119 | from the user. A character in Perl is logically just a number ranging | |
120 | from 0 to 2**32 or so. Larger characters encode to longer sequences | |
121 | of bytes internally, but again, this is just an internal detail which | |
122 | is hidden at the Perl level. | |
393fec97 | 123 | |
8cbd9a7a | 124 | =head2 Effects of character semantics |
393fec97 GS |
125 | |
126 | Character semantics have the following effects: | |
127 | ||
128 | =over 4 | |
129 | ||
130 | =item * | |
131 | ||
132 | Strings and patterns may contain characters that have an ordinal value | |
21bad921 | 133 | larger than 255. |
393fec97 | 134 | |
75daf61c JH |
135 | Presuming you use a Unicode editor to edit your program, such |
136 | characters will typically occur directly within the literal strings as | |
137 | UTF-8 (or UTF-EBCDIC on EBCDIC platforms) characters, but you can also | |
138 | specify a particular character with an extension of the C<\x> | |
139 | notation. UTF-X characters are specified by putting the hexadecimal | |
140 | code within curlies after the C<\x>. For instance, a Unicode smiley | |
141 | face is C<\x{263A}>. | |
393fec97 GS |
142 | |
143 | =item * | |
144 | ||
145 | Identifiers within the Perl script may contain Unicode alphanumeric | |
146 | characters, including ideographs. (You are currently on your own when | |
75daf61c JH |
147 | it comes to using the canonical forms of characters--Perl doesn't |
148 | (yet) attempt to canonicalize variable names for you.) | |
393fec97 | 149 | |
393fec97 GS |
150 | =item * |
151 | ||
152 | Regular expressions match characters instead of bytes. For instance, | |
153 | "." matches a character instead of a byte. (However, the C<\C> pattern | |
75daf61c | 154 | is provided to force a match a single byte ("C<char>" in C, hence C<\C>).) |
393fec97 | 155 | |
393fec97 GS |
156 | =item * |
157 | ||
158 | Character classes in regular expressions match characters instead of | |
159 | bytes, and match against the character properties specified in the | |
75daf61c JH |
160 | Unicode properties database. So C<\w> can be used to match an |
161 | ideograph, for instance. | |
393fec97 | 162 | |
393fec97 GS |
163 | =item * |
164 | ||
165 | Named Unicode properties and block ranges make be used as character | |
166 | classes via the new C<\p{}> (matches property) and C<\P{}> (doesn't | |
167 | match property) constructs. For instance, C<\p{Lu}> matches any | |
168 | character with the Unicode uppercase property, while C<\p{M}> matches | |
9fdf68be JH |
169 | any mark character. Single letter properties may omit the brackets, |
170 | so that can be written C<\pM> also. Many predefined character classes | |
171 | are available, such as C<\p{IsMirrored}> and C<\p{InTibetan}>. The | |
75daf61c JH |
172 | names of the C<In> classes are the official Unicode script and block |
173 | names but with all non-alphanumeric characters removed, for example | |
174 | the block name C<"Latin-1 Supplement"> becomes C<\p{InLatin1Supplement}>. | |
393fec97 | 175 | |
32293815 | 176 | Here is the list as of Unicode 3.1.0 (the two-letter classes) and |
2796c109 JH |
177 | as defined by Perl (the one-letter classes) (in Unicode materials |
178 | what Perl calls C<L> is often called C<L&>): | |
32293815 JH |
179 | |
180 | L Letter | |
181 | Lu Letter, Uppercase | |
182 | Ll Letter, Lowercase | |
183 | Lt Letter, Titlecase | |
184 | Lm Letter, Modifier | |
185 | Lo Letter, Other | |
186 | M Mark | |
187 | Mn Mark, Non-Spacing | |
188 | Mc Mark, Spacing Combining | |
189 | Me Mark, Enclosing | |
190 | N Number | |
191 | Nd Number, Decimal Digit | |
192 | Nl Number, Letter | |
193 | No Number, Other | |
194 | P Punctuation | |
195 | Pc Punctuation, Connector | |
196 | Pd Punctuation, Dash | |
197 | Ps Punctuation, Open | |
198 | Pe Punctuation, Close | |
199 | Pi Punctuation, Initial quote | |
200 | (may behave like Ps or Pe depending on usage) | |
201 | Pf Punctuation, Final quote | |
202 | (may behave like Ps or Pe depending on usage) | |
203 | Po Punctuation, Other | |
204 | S Symbol | |
205 | Sm Symbol, Math | |
206 | Sc Symbol, Currency | |
207 | Sk Symbol, Modifier | |
208 | So Symbol, Other | |
209 | Z Separator | |
210 | Zs Separator, Space | |
211 | Zl Separator, Line | |
212 | Zp Separator, Paragraph | |
213 | C Other | |
214 | Cc Other, Control | |
215 | Cf Other, Format | |
216 | Cs Other, Surrogate | |
217 | Co Other, Private Use | |
218 | Cn Other, Not Assigned (Unicode defines no Cn characters) | |
219 | ||
220 | Additionally, because scripts differ in their directionality | |
221 | (for example Hebrew is written right to left), all characters | |
222 | have their directionality defined: | |
223 | ||
224 | BidiL Left-to-Right | |
225 | BidiLRE Left-to-Right Embedding | |
226 | BidiLRO Left-to-Right Override | |
227 | BidiR Right-to-Left | |
228 | BidiAL Right-to-Left Arabic | |
229 | BidiRLE Right-to-Left Embedding | |
230 | BidiRLO Right-to-Left Override | |
231 | BidiPDF Pop Directional Format | |
232 | BidiEN European Number | |
233 | BidiES European Number Separator | |
234 | BidiET European Number Terminator | |
235 | BidiAN Arabic Number | |
236 | BidiCS Common Number Separator | |
237 | BidiNSM Non-Spacing Mark | |
238 | BidiBN Boundary Neutral | |
239 | BidiB Paragraph Separator | |
240 | BidiS Segment Separator | |
241 | BidiWS Whitespace | |
242 | BidiON Other Neutrals | |
243 | ||
2796c109 JH |
244 | =head2 Scripts |
245 | ||
75daf61c JH |
246 | The scripts available for C<\p{In...}> and C<\P{In...}>, for example |
247 | \p{InCyrillic>, are as follows, for example C<\p{InLatin}> or C<\P{InHan}>: | |
2796c109 JH |
248 | |
249 | Latin | |
250 | Greek | |
251 | Cyrillic | |
252 | Armenian | |
253 | Hebrew | |
254 | Arabic | |
255 | Syriac | |
256 | Thaana | |
257 | Devanagari | |
258 | Bengali | |
259 | Gurmukhi | |
260 | Gujarati | |
261 | Oriya | |
262 | Tamil | |
263 | Telugu | |
264 | Kannada | |
265 | Malayalam | |
266 | Sinhala | |
267 | Thai | |
268 | Lao | |
269 | Tibetan | |
270 | Myanmar | |
271 | Georgian | |
272 | Hangul | |
273 | Ethiopic | |
274 | Cherokee | |
275 | CanadianAboriginal | |
276 | Ogham | |
277 | Runic | |
278 | Khmer | |
279 | Mongolian | |
280 | Hiragana | |
281 | Katakana | |
282 | Bopomofo | |
283 | Han | |
284 | Yi | |
285 | OldItalic | |
286 | Gothic | |
287 | Deseret | |
288 | Inherited | |
289 | ||
290 | =head2 Blocks | |
291 | ||
292 | In addition to B<scripts>, Unicode also defines B<blocks> of | |
293 | characters. The difference between scripts and blocks is that the | |
294 | former concept is closer to natural languages, while the latter | |
295 | concept is more an artificial grouping based on groups of 256 Unicode | |
296 | characters. For example, the C<Latin> script contains letters from | |
297 | many blocks, but it does not contain all the characters from those | |
298 | blocks, it does not for example contain digits. | |
299 | ||
300 | For more about scripts see the UTR #24: | |
301 | http://www.unicode.org/unicode/reports/tr24/ | |
302 | For more about blocks see | |
303 | http://www.unicode.org/Public/UNIDATA/Blocks.txt | |
304 | ||
305 | Because there are overlaps in naming (there are, for example, both | |
306 | a script called C<Katakana> and a block called C<Katakana>, the block | |
307 | version has C<Block> appended to its name, C<\p{InKatakanaBlock}>. | |
308 | ||
309 | Notice that this definition was introduced in Perl 5.8.0: in Perl | |
310 | 5.6.0 only the blocks were used; in Perl 5.8.0 scripts became the | |
311 | preferential character class definition; this meant that the | |
312 | definitions of some character classes changed (the ones in the | |
313 | below list that have the C<Block> appended). | |
314 | ||
315 | BasicLatin | |
316 | Latin1Supplement | |
317 | LatinExtendedA | |
318 | LatinExtendedB | |
319 | IPAExtensions | |
320 | SpacingModifierLetters | |
321 | CombiningDiacriticalMarks | |
322 | GreekBlock | |
323 | CyrillicBlock | |
324 | ArmenianBlock | |
325 | HebrewBlock | |
326 | ArabicBlock | |
327 | SyriacBlock | |
328 | ThaanaBlock | |
329 | DevanagariBlock | |
330 | BengaliBlock | |
331 | GurmukhiBlock | |
332 | GujaratiBlock | |
333 | OriyaBlock | |
334 | TamilBlock | |
335 | TeluguBlock | |
336 | KannadaBlock | |
337 | MalayalamBlock | |
338 | SinhalaBlock | |
339 | ThaiBlock | |
340 | LaoBlock | |
341 | TibetanBlock | |
342 | MyanmarBlock | |
343 | GeorgianBlock | |
344 | HangulJamo | |
345 | EthiopicBlock | |
346 | CherokeeBlock | |
347 | UnifiedCanadianAboriginalSyllabics | |
348 | OghamBlock | |
349 | RunicBlock | |
350 | KhmerBlock | |
351 | MongolianBlock | |
352 | LatinExtendedAdditional | |
353 | GreekExtended | |
354 | GeneralPunctuation | |
355 | SuperscriptsandSubscripts | |
356 | CurrencySymbols | |
357 | CombiningMarksforSymbols | |
358 | LetterlikeSymbols | |
359 | NumberForms | |
360 | Arrows | |
361 | MathematicalOperators | |
362 | MiscellaneousTechnical | |
363 | ControlPictures | |
364 | OpticalCharacterRecognition | |
365 | EnclosedAlphanumerics | |
366 | BoxDrawing | |
367 | BlockElements | |
368 | GeometricShapes | |
369 | MiscellaneousSymbols | |
370 | Dingbats | |
371 | BraillePatterns | |
372 | CJKRadicalsSupplement | |
373 | KangxiRadicals | |
374 | IdeographicDescriptionCharacters | |
375 | CJKSymbolsandPunctuation | |
376 | HiraganaBlock | |
377 | KatakanaBlock | |
378 | BopomofoBlock | |
379 | HangulCompatibilityJamo | |
380 | Kanbun | |
381 | BopomofoExtended | |
382 | EnclosedCJKLettersandMonths | |
383 | CJKCompatibility | |
384 | CJKUnifiedIdeographsExtensionA | |
385 | CJKUnifiedIdeographs | |
386 | YiSyllables | |
387 | YiRadicals | |
388 | HangulSyllables | |
389 | HighSurrogates | |
390 | HighPrivateUseSurrogates | |
391 | LowSurrogates | |
392 | PrivateUse | |
393 | CJKCompatibilityIdeographs | |
394 | AlphabeticPresentationForms | |
395 | ArabicPresentationFormsA | |
396 | CombiningHalfMarks | |
397 | CJKCompatibilityForms | |
398 | SmallFormVariants | |
399 | ArabicPresentationFormsB | |
400 | Specials | |
401 | HalfwidthandFullwidthForms | |
402 | OldItalicBlock | |
403 | GothicBlock | |
404 | DeseretBlock | |
405 | ByzantineMusicalSymbols | |
406 | MusicalSymbols | |
407 | MathematicalAlphanumericSymbols | |
408 | CJKUnifiedIdeographsExtensionB | |
409 | CJKCompatibilityIdeographsSupplement | |
410 | Tags | |
32293815 | 411 | |
393fec97 GS |
412 | =item * |
413 | ||
414 | The special pattern C<\X> match matches any extended Unicode sequence | |
415 | (a "combining character sequence" in Standardese), where the first | |
416 | character is a base character and subsequent characters are mark | |
417 | characters that apply to the base character. It is equivalent to | |
418 | C<(?:\PM\pM*)>. | |
419 | ||
393fec97 GS |
420 | =item * |
421 | ||
383e7cdd JH |
422 | The C<tr///> operator translates characters instead of bytes. Note |
423 | that the C<tr///CU> functionality has been removed, as the interface | |
424 | was a mistake. For similar functionality see pack('U0', ...) and | |
425 | pack('C0', ...). | |
393fec97 | 426 | |
393fec97 GS |
427 | =item * |
428 | ||
429 | Case translation operators use the Unicode case translation tables | |
430 | when provided character input. Note that C<uc()> translates to | |
431 | uppercase, while C<ucfirst> translates to titlecase (for languages | |
432 | that make the distinction). Naturally the corresponding backslash | |
433 | sequences have the same semantics. | |
434 | ||
435 | =item * | |
436 | ||
437 | Most operators that deal with positions or lengths in the string will | |
75daf61c JH |
438 | automatically switch to using character positions, including |
439 | C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>, | |
440 | C<sprintf()>, C<write()>, and C<length()>. Operators that | |
441 | specifically don't switch include C<vec()>, C<pack()>, and | |
442 | C<unpack()>. Operators that really don't care include C<chomp()>, as | |
443 | well as any other operator that treats a string as a bucket of bits, | |
444 | such as C<sort()>, and the operators dealing with filenames. | |
393fec97 GS |
445 | |
446 | =item * | |
447 | ||
448 | The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change, | |
449 | since they're often used for byte-oriented formats. (Again, think | |
450 | "C<char>" in the C language.) However, there is a new "C<U>" specifier | |
451 | that will convert between UTF-8 characters and integers. (It works | |
452 | outside of the utf8 pragma too.) | |
453 | ||
454 | =item * | |
455 | ||
456 | The C<chr()> and C<ord()> functions work on characters. This is like | |
457 | C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and | |
458 | C<unpack("C")>. In fact, the latter are how you now emulate | |
35bcd338 JH |
459 | byte-oriented C<chr()> and C<ord()> for Unicode strings. |
460 | (Note that this reveals the internal UTF-8 encoding of strings and | |
461 | you are not supposed to do that unless you know what you are doing.) | |
393fec97 GS |
462 | |
463 | =item * | |
464 | ||
a1ca4561 YST |
465 | The bit string operators C<& | ^ ~> can operate on character data. |
466 | However, for backward compatibility reasons (bit string operations | |
75daf61c JH |
467 | when the characters all are less than 256 in ordinal value) one should |
468 | not mix C<~> (the bit complement) and characters both less than 256 and | |
a1ca4561 YST |
469 | equal or greater than 256. Most importantly, the DeMorgan's laws |
470 | (C<~($x|$y) eq ~$x&~$y>, C<~($x&$y) eq ~$x|~$y>) won't hold. | |
471 | Another way to look at this is that the complement cannot return | |
75daf61c | 472 | B<both> the 8-bit (byte) wide bit complement B<and> the full character |
a1ca4561 YST |
473 | wide bit complement. |
474 | ||
475 | =item * | |
476 | ||
393fec97 GS |
477 | And finally, C<scalar reverse()> reverses by character rather than by byte. |
478 | ||
479 | =back | |
480 | ||
8cbd9a7a GS |
481 | =head2 Character encodings for input and output |
482 | ||
7221edc9 | 483 | See L<Encode>. |
8cbd9a7a | 484 | |
393fec97 GS |
485 | =head1 CAVEATS |
486 | ||
487 | As of yet, there is no method for automatically coercing input and | |
b3419ed8 PK |
488 | output to some encoding other than UTF-8 or UTF-EBCDIC. This is planned |
489 | in the near future, however. | |
393fec97 | 490 | |
8cbd9a7a GS |
491 | Whether an arbitrary piece of data will be treated as "characters" or |
492 | "bytes" by internal operations cannot be divined at the current time. | |
393fec97 GS |
493 | |
494 | Use of locales with utf8 may lead to odd results. Currently there is | |
495 | some attempt to apply 8-bit locale info to characters in the range | |
496 | 0..255, but this is demonstrably incorrect for locales that use | |
497 | characters above that range (when mapped into Unicode). It will also | |
498 | tend to run slower. Avoidance of locales is strongly encouraged. | |
499 | ||
500 | =head1 SEE ALSO | |
501 | ||
32293815 | 502 | L<bytes>, L<utf8>, L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}"> |
393fec97 GS |
503 | |
504 | =cut |