1charnames(3pm)         Perl Programmers Reference Guide         charnames(3pm)
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NAME

6       charnames - access to Unicode character names and named character
7       sequences; also define character names
8

SYNOPSIS

10        use charnames ':full';
11        print "\N{GREEK SMALL LETTER SIGMA} is called sigma.\n";
12        print "\N{LATIN CAPITAL LETTER E WITH VERTICAL LINE BELOW}",
13              " is an officially named sequence of two Unicode characters\n";
14
15        use charnames ':loose';
16        print "\N{Greek small-letter  sigma}",
17               "can be used to ignore case, underscores, most blanks,"
18               "and when you aren't sure if the official name has hyphens\n";
19
20        use charnames ':short';
21        print "\N{greek:Sigma} is an upper-case sigma.\n";
22
23        use charnames qw(cyrillic greek);
24        print "\N{sigma} is Greek sigma, and \N{be} is Cyrillic b.\n";
25
26        use charnames ":full", ":alias" => {
27          e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
28          mychar => 0xE8000,  # Private use area
29        };
30        print "\N{e_ACUTE} is a small letter e with an acute.\n";
31        print "\N{mychar} allows me to name private use characters.\n";
32
33        use charnames ();
34        print charnames::viacode(0x1234); # prints "ETHIOPIC SYLLABLE SEE"
35        printf "%04X", charnames::vianame("GOTHIC LETTER AHSA"); # prints
36                                                                 # "10330"
37        print charnames::vianame("LATIN CAPITAL LETTER A"); # prints 65 on
38                                                            # ASCII platforms;
39                                                            # 193 on EBCDIC
40        print charnames::string_vianame("LATIN CAPITAL LETTER A"); # prints "A"
41

DESCRIPTION

43       Pragma "use charnames" is used to gain access to the names of the
44       Unicode characters and named character sequences, and to allow you to
45       define your own character and character sequence names.
46
47       All forms of the pragma enable use of the following 3 functions:
48
49       ·   "charnames::string_vianame(name)" for run-time lookup of a either a
50           character name or a named character sequence, returning its string
51           representation
52
53       ·   "charnames::vianame(name)" for run-time lookup of a character name
54           (but not a named character sequence) to get its ordinal value (code
55           point)
56
57       ·   "charnames::viacode(code)" for run-time lookup of a code point to
58           get its Unicode name.
59
60       Starting in Perl v5.16, any occurrence of "\N{CHARNAME}" sequences in a
61       double-quotish string automatically loads this module with arguments
62       ":full" and ":short" (described below) if it hasn't already been loaded
63       with different arguments, in order to compile the named Unicode
64       character into position in the string.  Prior to v5.16, an explicit
65       "use charnames" was required to enable this usage.  (However, prior to
66       v5.16, the form "use charnames ();" did not enable "\N{CHARNAME}".)
67
68       Note that "\N{U+...}", where the ... is a hexadecimal number, also
69       inserts a character into a string.  The character it inserts is the one
70       whose code point (ordinal value) is equal to the number.  For example,
71       "\N{U+263a}" is the Unicode (white background, black foreground) smiley
72       face equivalent to "\N{WHITE SMILING FACE}".  Also note, "\N{...}" can
73       mean a regex quantifier instead of a character name, when the ... is a
74       number (or comma separated pair of numbers (see "QUANTIFIERS" in
75       perlreref), and is not related to this pragma.
76
77       The "charnames" pragma supports arguments ":full", ":loose", ":short",
78       script names and customized aliases.
79
80       If ":full" is present, for expansion of "\N{CHARNAME}", the string
81       CHARNAME is first looked up in the list of standard Unicode character
82       names.
83
84       ":loose" is a variant of ":full" which allows CHARNAME to be less
85       precisely specified.  Details are in "LOOSE MATCHES".
86
87       If ":short" is present, and CHARNAME has the form "SCRIPT:CNAME", then
88       CNAME is looked up as a letter in script SCRIPT, as described in the
89       next paragraph.  Or, if "use charnames" is used with script name
90       arguments, then for "\N{CHARNAME}" the name CHARNAME is looked up as a
91       letter in the given scripts (in the specified order). Customized
92       aliases can override these, and are explained in "CUSTOM ALIASES".
93
94       For lookup of CHARNAME inside a given script SCRIPTNAME, this pragma
95       looks in the table of standard Unicode names for the names
96
97         SCRIPTNAME CAPITAL LETTER CHARNAME
98         SCRIPTNAME SMALL LETTER CHARNAME
99         SCRIPTNAME LETTER CHARNAME
100
101       If CHARNAME is all lowercase, then the "CAPITAL" variant is ignored,
102       otherwise the "SMALL" variant is ignored, and both CHARNAME and
103       SCRIPTNAME are converted to all uppercase for look-up.  Other than
104       that, both of them follow loose rules if ":loose" is also specified;
105       strict otherwise.
106
107       Note that "\N{...}" is compile-time; it's a special form of string
108       constant used inside double-quotish strings; this means that you cannot
109       use variables inside the "\N{...}".  If you want similar run-time
110       functionality, use charnames::string_vianame().
111
112       Since Unicode 6.0, it is deprecated to use "BELL".  Instead use "ALERT"
113       (but "BEL" will continue to work).
114
115       If the input name is unknown, "\N{NAME}" raises a warning and
116       substitutes the Unicode REPLACEMENT CHARACTER (U+FFFD).
117
118       For "\N{NAME}", it is a fatal error if "use bytes" is in effect and the
119       input name is that of a character that won't fit into a byte (i.e.,
120       whose ordinal is above 255).
121
122       Otherwise, any string that includes a "\N{charname}" or
123       "\N{U+code point}" will automatically have Unicode semantics (see "Byte
124       and Character Semantics" in perlunicode).
125

LOOSE MATCHES

127       By specifying ":loose", Unicode's loose character name matching
128       <http://www.unicode.org/reports/tr44#Matching_Rules> rules are selected
129       instead of the strict exact match used otherwise.  That means that
130       CHARNAME doesn't have to be so precisely specified.  Upper/lower case
131       doesn't matter (except with scripts as mentioned above), nor do any
132       underscores, and the only hyphens that matter are those at the
133       beginning or end of a word in the name (with one exception:  the hyphen
134       in U+1180 "HANGUL JUNGSEONG O-E" does matter).  Also, blanks not
135       adjacent to hyphens don't matter.  The official Unicode names are quite
136       variable as to where they use hyphens versus spaces to separate word-
137       like units, and this option allows you to not have to care as much.
138       The reason non-medial hyphens matter is because of cases like U+0F60
139       "TIBETAN LETTER -A" versus U+0F68 "TIBETAN LETTER A".  The hyphen here
140       is significant, as is the space before it, and so both must be
141       included.
142
143       ":loose" slows down look-ups by a factor of 2 to 3 versus ":full", but
144       the trade-off may be worth it to you.  Each individual look-up takes
145       very little time, and the results are cached, so the speed difference
146       would become a factor only in programs that do look-ups of many
147       different spellings, and probably only when those look-ups are through
148       vianame() and string_vianame(), since "\N{...}" look-ups are done at
149       compile time.
150

ALIASES

152       Starting in Unicode 6.1 and Perl v5.16, Unicode defines many
153       abbreviations and names that were formerly Perl extensions, and some
154       additional ones that Perl did not previously accept.  The list is
155       getting too long to reproduce here, but you can get the complete list
156       from the Unicode web site:
157       <http://www.unicode.org/Public/UNIDATA/NameAliases.txt>.
158
159       Earlier versions of Perl accepted almost all the 6.1 names.  These were
160       most extensively documented in the v5.14 version of this pod:
161       <http://perldoc.perl.org/5.14.0/charnames.html#ALIASES>.
162

CUSTOM ALIASES

164       You can add customized aliases to standard (":full") Unicode naming
165       conventions.  The aliases override any standard definitions, so, if
166       you're twisted enough, you can change "\N{LATIN CAPITAL LETTER A}" to
167       mean "B", etc.
168
169       Note that an alias should not be something that is a legal curly brace-
170       enclosed quantifier (see "QUANTIFIERS" in perlreref).  For example
171       "\N{123}" means to match 123 non-newline characters, and is not treated
172       as a charnames alias.  Aliases are discouraged from beginning with
173       anything other than an alphabetic character and from containing
174       anything other than alphanumerics, spaces, dashes, parentheses, and
175       underscores.  Currently they must be ASCII.
176
177       An alias can map to either an official Unicode character name (not a
178       loose matched name) or to a numeric code point (ordinal).  The latter
179       is useful for assigning names to code points in Unicode private use
180       areas such as U+E800 through U+F8FF.  A numeric code point must be a
181       non-negative integer or a string beginning with "U+" or "0x" with the
182       remainder considered to be a hexadecimal integer.  A literal numeric
183       constant must be unsigned; it will be interpreted as hex if it has a
184       leading zero or contains non-decimal hex digits; otherwise it will be
185       interpreted as decimal.
186
187       Aliases are added either by the use of anonymous hashes:
188
189           use charnames ":alias" => {
190               e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
191               mychar1 => 0xE8000,
192               };
193           my $str = "\N{e_ACUTE}";
194
195       or by using a file containing aliases:
196
197           use charnames ":alias" => "pro";
198
199       This will try to read "unicore/pro_alias.pl" from the @INC path. This
200       file should return a list in plain perl:
201
202           (
203           A_GRAVE         => "LATIN CAPITAL LETTER A WITH GRAVE",
204           A_CIRCUM        => "LATIN CAPITAL LETTER A WITH CIRCUMFLEX",
205           A_DIAERES       => "LATIN CAPITAL LETTER A WITH DIAERESIS",
206           A_TILDE         => "LATIN CAPITAL LETTER A WITH TILDE",
207           A_BREVE         => "LATIN CAPITAL LETTER A WITH BREVE",
208           A_RING          => "LATIN CAPITAL LETTER A WITH RING ABOVE",
209           A_MACRON        => "LATIN CAPITAL LETTER A WITH MACRON",
210           mychar2         => "U+E8001",
211           );
212
213       Both these methods insert ":full" automatically as the first argument
214       (if no other argument is given), and you can give the ":full"
215       explicitly as well, like
216
217           use charnames ":full", ":alias" => "pro";
218
219       ":loose" has no effect with these.  Input names must match exactly,
220       using ":full" rules.
221
222       Also, both these methods currently allow only single characters to be
223       named.  To name a sequence of characters, use a custom translator
224       (described below).
225

charnames::string_vianame(name)

227       This is a runtime equivalent to "\N{...}".  name can be any expression
228       that evaluates to a name accepted by "\N{...}" under the ":full" option
229       to "charnames".  In addition, any other options for the controlling
230       "use charnames" in the same scope apply, like ":loose" or any script
231       list, ":short" option, or custom aliases you may have defined.
232
233       The only difference is that if the input name is unknown,
234       "string_vianame" returns "undef" instead of the REPLACEMENT CHARACTER
235       and does not raise a warning message.
236

charnames::vianame(name)

238       This is similar to "string_vianame".  The main difference is that under
239       most circumstances, vianame returns an ordinal code point, whereas
240       "string_vianame" returns a string.  For example,
241
242          printf "U+%04X", charnames::vianame("FOUR TEARDROP-SPOKED ASTERISK");
243
244       prints "U+2722".
245
246       This leads to the other two differences.  Since a single code point is
247       returned, the function can't handle named character sequences, as these
248       are composed of multiple characters (it returns "undef" for these.
249       And, the code point can be that of any character, even ones that aren't
250       legal under the "use bytes" pragma,
251
252       See "BUGS" for the circumstances in which the behavior differs from
253       that described above.
254

charnames::viacode(code)

256       Returns the full name of the character indicated by the numeric code.
257       For example,
258
259           print charnames::viacode(0x2722);
260
261       prints "FOUR TEARDROP-SPOKED ASTERISK".
262
263       The name returned is the "best" (defined below) official name or alias
264       for the code point, if available; otherwise your custom alias for it,
265       if defined; otherwise "undef".  This means that your alias will only be
266       returned for code points that don't have an official Unicode name (nor
267       alias) such as private use code points.
268
269       If you define more than one name for the code point, it is
270       indeterminate which one will be returned.
271
272       As mentioned, the function returns "undef" if no name is known for the
273       code point.  In Unicode the proper name of these is the empty string,
274       which "undef" stringifies to.  (If you ask for a code point past the
275       legal Unicode maximum of U+10FFFF that you haven't assigned an alias
276       to, you get "undef" plus a warning.)
277
278       The input number must be a non-negative integer, or a string beginning
279       with "U+" or "0x" with the remainder considered to be a hexadecimal
280       integer.  A literal numeric constant must be unsigned; it will be
281       interpreted as hex if it has a leading zero or contains non-decimal hex
282       digits; otherwise it will be interpreted as decimal.
283
284       As mentioned above under "ALIASES", Unicode 6.1 defines extra names
285       (synonyms or aliases) for some code points, most of which were already
286       available as Perl extensions.  All these are accepted by "\N{...}" and
287       the other functions in this module, but "viacode" has to choose which
288       one name to return for a given input code point, so it returns the
289       "best" name.  To understand how this works, it is helpful to know more
290       about the Unicode name properties.  All code points actually have only
291       a single name, which (starting in Unicode 2.0) can never change once a
292       character has been assigned to the code point.  But mistakes have been
293       made in assigning names, for example sometimes a clerical error was
294       made during the publishing of the Standard which caused words to be
295       misspelled, and there was no way to correct those.  The Name_Alias
296       property was eventually created to handle these situations.  If a name
297       was wrong, a corrected synonym would be published for it, using
298       Name_Alias.  "viacode" will return that corrected synonym as the "best"
299       name for a code point.  (It is even possible, though it hasn't happened
300       yet, that the correction itself will need to be corrected, and so
301       another Name_Alias can be created for that code point; "viacode" will
302       return the most recent correction.)
303
304       The Unicode name for each of the control characters (such as LINE FEED)
305       is the empty string.  However almost all had names assigned by other
306       standards, such as the ASCII Standard, or were in common use.
307       "viacode" returns these names as the "best" ones available.  Unicode
308       6.1 has created Name_Aliases for each of them, including alternate
309       names, like NEW LINE.  "viacode" uses the original name, "LINE FEED" in
310       preference to the alternate.  Similarly the name returned for U+FEFF is
311       "ZERO WIDTH NO-BREAK SPACE", not "BYTE ORDER MARK".
312
313       Until Unicode 6.1, the 4 control characters U+0080, U+0081, U+0084, and
314       U+0099 did not have names nor aliases.  To preserve backwards
315       compatibility, any alias you define for these code points will be
316       returned by this function, in preference to the official name.
317
318       Some code points also have abbreviated names, such as "LF" or "NL".
319       "viacode" never returns these.
320
321       Because a name correction may be added in future Unicode releases, the
322       name that "viacode" returns may change as a result.  This is a rare
323       event, but it does happen.
324

CUSTOM TRANSLATORS

326       The mechanism of translation of "\N{...}" escapes is general and not
327       hardwired into charnames.pm.  A module can install custom translations
328       (inside the scope which "use"s the module) with the following magic
329       incantation:
330
331           sub import {
332               shift;
333               $^H{charnames} = \&translator;
334           }
335
336       Here translator() is a subroutine which takes CHARNAME as an argument,
337       and returns text to insert into the string instead of the
338       "\N{CHARNAME}" escape.
339
340       This is the only way you can create a custom named sequence of code
341       points.
342
343       Since the text to insert should be different in "bytes" mode and out of
344       it, the function should check the current state of "bytes"-flag as in:
345
346           use bytes ();                      # for $bytes::hint_bits
347           sub translator {
348               if ($^H & $bytes::hint_bits) {
349                   return bytes_translator(@_);
350               }
351               else {
352                   return utf8_translator(@_);
353               }
354           }
355
356       See "CUSTOM ALIASES" above for restrictions on CHARNAME.
357
358       Of course, "vianame", "viacode", and "string_vianame" would need to be
359       overridden as well.
360

BUGS

362       vianame() normally returns an ordinal code point, but when the input
363       name is of the form "U+...", it returns a chr instead.  In this case,
364       if "use bytes" is in effect and the character won't fit into a byte, it
365       returns "undef" and raises a warning.
366
367       Names must be ASCII characters only, which means that you are out of
368       luck if you want to create aliases in a language where some or all the
369       characters of the desired aliases are non-ASCII.
370
371       Since evaluation of the translation function (see "CUSTOM TRANSLATORS")
372       happens in the middle of compilation (of a string literal), the
373       translation function should not do any "eval"s or "require"s.  This
374       restriction should be lifted (but is low priority) in a future version
375       of Perl.
376
377
378
379perl v5.16.3                      2013-03-04                    charnames(3pm)
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