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 utf8;
27        use charnames ":full", ":alias" => {
28          e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
29          mychar => 0xE8000,  # Private use area
30          "XXXXXXX" => "BICYCLIST"
31        };
32        print "\N{e_ACUTE} is a small letter e with an acute.\n";
33        print "\N{mychar} allows me to name private use characters.\n";
34        print "And I can create synonyms in other languages,",
35              " such as \N{XXXXXXX} for "BICYCLIST (U+1F6B4)\n";
36
37        use charnames ();
38        print charnames::viacode(0x1234); # prints "ETHIOPIC SYLLABLE SEE"
39        printf "%04X", charnames::vianame("GOTHIC LETTER AHSA"); # prints
40                                                                 # "10330"
41        print charnames::vianame("LATIN CAPITAL LETTER A"); # prints 65 on
42                                                            # ASCII platforms;
43                                                            # 193 on EBCDIC
44        print charnames::string_vianame("LATIN CAPITAL LETTER A"); # prints "A"
45

DESCRIPTION

47       Pragma "use charnames" is used to gain access to the names of the
48       Unicode characters and named character sequences, and to allow you to
49       define your own character and character sequence names.
50
51       All forms of the pragma enable use of the following 3 functions:
52
53       ·   "charnames::string_vianame(name)" for run-time lookup of a either a
54           character name or a named character sequence, returning its string
55           representation
56
57       ·   "charnames::vianame(name)" for run-time lookup of a character name
58           (but not a named character sequence) to get its ordinal value (code
59           point)
60
61       ·   "charnames::viacode(code)" for run-time lookup of a code point to
62           get its Unicode name.
63
64       Starting in Perl v5.16, any occurrence of "\N{CHARNAME}" sequences in a
65       double-quotish string automatically loads this module with arguments
66       ":full" and ":short" (described below) if it hasn't already been loaded
67       with different arguments, in order to compile the named Unicode
68       character into position in the string.  Prior to v5.16, an explicit
69       "use charnames" was required to enable this usage.  (However, prior to
70       v5.16, the form "use charnames ();" did not enable "\N{CHARNAME}".)
71
72       Note that "\N{U+...}", where the ... is a hexadecimal number, also
73       inserts a character into a string.  The character it inserts is the one
74       whose Unicode code point (ordinal value) is equal to the number.  For
75       example, "\N{U+263a}" is the Unicode (white background, black
76       foreground) smiley face equivalent to "\N{WHITE SMILING FACE}".  Also
77       note, "\N{...}" can mean a regex quantifier instead of a character
78       name, when the ... is a number (or comma separated pair of numbers (see
79       "QUANTIFIERS" in perlreref), and is not related to this pragma.
80
81       The "charnames" pragma supports arguments ":full", ":loose", ":short",
82       script names and customized aliases.
83
84       If ":full" is present, for expansion of "\N{CHARNAME}", the string
85       CHARNAME is first looked up in the list of standard Unicode character
86       names.
87
88       ":loose" is a variant of ":full" which allows CHARNAME to be less
89       precisely specified.  Details are in "LOOSE MATCHES".
90
91       If ":short" is present, and CHARNAME has the form "SCRIPT:CNAME", then
92       CNAME is looked up as a letter in script SCRIPT, as described in the
93       next paragraph.  Or, if "use charnames" is used with script name
94       arguments, then for "\N{CHARNAME}" the name CHARNAME is looked up as a
95       letter in the given scripts (in the specified order). Customized
96       aliases can override these, and are explained in "CUSTOM ALIASES".
97
98       For lookup of CHARNAME inside a given script SCRIPTNAME, this pragma
99       looks in the table of standard Unicode names for the names
100
101         SCRIPTNAME CAPITAL LETTER CHARNAME
102         SCRIPTNAME SMALL LETTER CHARNAME
103         SCRIPTNAME LETTER CHARNAME
104
105       If CHARNAME is all lowercase, then the "CAPITAL" variant is ignored,
106       otherwise the "SMALL" variant is ignored, and both CHARNAME and
107       SCRIPTNAME are converted to all uppercase for look-up.  Other than
108       that, both of them follow loose rules if ":loose" is also specified;
109       strict otherwise.
110
111       Note that "\N{...}" is compile-time; it's a special form of string
112       constant used inside double-quotish strings; this means that you cannot
113       use variables inside the "\N{...}".  If you want similar run-time
114       functionality, use charnames::string_vianame().
115
116       Note, starting in Perl 5.18, the name "BELL" refers to the Unicode
117       character U+1F514, instead of the traditional U+0007.  For the latter,
118       use "ALERT" or "BEL".
119
120       It is a syntax error to use "\N{NAME}" where "NAME" is unknown.
121
122       For "\N{NAME}", it is a fatal error if "use bytes" is in effect and the
123       input name is that of a character that won't fit into a byte (i.e.,
124       whose ordinal is above 255).
125
126       Otherwise, any string that includes a "\N{charname}" or
127       "\N{U+code point}" will automatically have Unicode rules (see "Byte and
128       Character Semantics" in perlunicode).
129

LOOSE MATCHES

131       By specifying ":loose", Unicode's loose character name matching
132       <http://www.unicode.org/reports/tr44#Matching_Rules> rules are selected
133       instead of the strict exact match used otherwise.  That means that
134       CHARNAME doesn't have to be so precisely specified.  Upper/lower case
135       doesn't matter (except with scripts as mentioned above), nor do any
136       underscores, and the only hyphens that matter are those at the
137       beginning or end of a word in the name (with one exception:  the hyphen
138       in U+1180 "HANGUL JUNGSEONG O-E" does matter).  Also, blanks not
139       adjacent to hyphens don't matter.  The official Unicode names are quite
140       variable as to where they use hyphens versus spaces to separate word-
141       like units, and this option allows you to not have to care as much.
142       The reason non-medial hyphens matter is because of cases like U+0F60
143       "TIBETAN LETTER -A" versus U+0F68 "TIBETAN LETTER A".  The hyphen here
144       is significant, as is the space before it, and so both must be
145       included.
146
147       ":loose" slows down look-ups by a factor of 2 to 3 versus ":full", but
148       the trade-off may be worth it to you.  Each individual look-up takes
149       very little time, and the results are cached, so the speed difference
150       would become a factor only in programs that do look-ups of many
151       different spellings, and probably only when those look-ups are through
152       "vianame()" and "string_vianame()", since "\N{...}" look-ups are done
153       at compile time.
154

ALIASES

156       Starting in Unicode 6.1 and Perl v5.16, Unicode defines many
157       abbreviations and names that were formerly Perl extensions, and some
158       additional ones that Perl did not previously accept.  The list is
159       getting too long to reproduce here, but you can get the complete list
160       from the Unicode web site:
161       <http://www.unicode.org/Public/UNIDATA/NameAliases.txt>.
162
163       Earlier versions of Perl accepted almost all the 6.1 names.  These were
164       most extensively documented in the v5.14 version of this pod:
165       <http://perldoc.perl.org/5.14.0/charnames.html#ALIASES>.
166

CUSTOM ALIASES

168       You can add customized aliases to standard (":full") Unicode naming
169       conventions.  The aliases override any standard definitions, so, if
170       you're twisted enough, you can change "\N{LATIN CAPITAL LETTER A}" to
171       mean "B", etc.
172
173       Aliases must begin with a character that is alphabetic.  After that,
174       each may contain any combination of word ("\w") characters, SPACE
175       (U+0020), HYPHEN-MINUS (U+002D), LEFT PARENTHESIS (U+0028), and RIGHT
176       PARENTHESIS (U+0029).  These last two should never have been allowed in
177       names, and are retained for backwards compatibility only, and may be
178       deprecated and removed in future releases of Perl, so don't use them
179       for new names.  (More precisely, the first character of a name you
180       specify must be something that matches all of "\p{ID_Start}",
181       "\p{Alphabetic}", and "\p{Gc=Letter}".  This makes sure it is what any
182       reasonable person would view as an alphabetic character.  And, the
183       continuation characters that match "\w" must also match
184       "\p{ID_Continue}".)  Starting with Perl v5.18, any Unicode characters
185       meeting the above criteria may be used; prior to that only Latin1-range
186       characters were acceptable.
187
188       An alias can map to either an official Unicode character name (not a
189       loose matched name) or to a numeric code point (ordinal).  The latter
190       is useful for assigning names to code points in Unicode private use
191       areas such as U+E800 through U+F8FF.  A numeric code point must be a
192       non-negative integer, or a string beginning with "U+" or "0x" with the
193       remainder considered to be a hexadecimal integer.  A literal numeric
194       constant must be unsigned; it will be interpreted as hex if it has a
195       leading zero or contains non-decimal hex digits; otherwise it will be
196       interpreted as decimal.  If it begins with "U+", it is interpreted as
197       the Unicode code point; otherwise it is interpreted as native.  (Only
198       code points below 256 can differ between Unicode and native.)  Thus
199       "U+41" is always the Latin letter "A"; but 0x41 can be "NO-BREAK SPACE"
200       on EBCDIC platforms.
201
202       Aliases are added either by the use of anonymous hashes:
203
204           use charnames ":alias" => {
205               e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
206               mychar1 => 0xE8000,
207               };
208           my $str = "\N{e_ACUTE}";
209
210       or by using a file containing aliases:
211
212           use charnames ":alias" => "pro";
213
214       This will try to read "unicore/pro_alias.pl" from the @INC path. This
215       file should return a list in plain perl:
216
217           (
218           A_GRAVE         => "LATIN CAPITAL LETTER A WITH GRAVE",
219           A_CIRCUM        => "LATIN CAPITAL LETTER A WITH CIRCUMFLEX",
220           A_DIAERES       => "LATIN CAPITAL LETTER A WITH DIAERESIS",
221           A_TILDE         => "LATIN CAPITAL LETTER A WITH TILDE",
222           A_BREVE         => "LATIN CAPITAL LETTER A WITH BREVE",
223           A_RING          => "LATIN CAPITAL LETTER A WITH RING ABOVE",
224           A_MACRON        => "LATIN CAPITAL LETTER A WITH MACRON",
225           mychar2         => "U+E8001",
226           );
227
228       Both these methods insert ":full" automatically as the first argument
229       (if no other argument is given), and you can give the ":full"
230       explicitly as well, like
231
232           use charnames ":full", ":alias" => "pro";
233
234       ":loose" has no effect with these.  Input names must match exactly,
235       using ":full" rules.
236
237       Also, both these methods currently allow only single characters to be
238       named.  To name a sequence of characters, use a custom translator
239       (described below).
240

charnames::string_vianame(name)

242       This is a runtime equivalent to "\N{...}".  name can be any expression
243       that evaluates to a name accepted by "\N{...}" under the ":full" option
244       to "charnames".  In addition, any other options for the controlling
245       "use charnames" in the same scope apply, like ":loose" or any script
246       list, ":short" option, or custom aliases you may have defined.
247
248       The only differences are due to the fact that "string_vianame" is run-
249       time and "\N{}" is compile time.  You can't interpolate inside a
250       "\N{}", (so "\N{$variable}" doesn't work); and if the input name is
251       unknown, "string_vianame" returns "undef" instead of it being a syntax
252       error.
253

charnames::vianame(name)

255       This is similar to "string_vianame".  The main difference is that under
256       most circumstances, "vianame" returns an ordinal code point, whereas
257       "string_vianame" returns a string.  For example,
258
259          printf "U+%04X", charnames::vianame("FOUR TEARDROP-SPOKED ASTERISK");
260
261       prints "U+2722".
262
263       This leads to the other two differences.  Since a single code point is
264       returned, the function can't handle named character sequences, as these
265       are composed of multiple characters (it returns "undef" for these.
266       And, the code point can be that of any character, even ones that aren't
267       legal under the "use bytes" pragma,
268
269       See "BUGS" for the circumstances in which the behavior differs from
270       that described above.
271

charnames::viacode(code)

273       Returns the full name of the character indicated by the numeric code.
274       For example,
275
276           print charnames::viacode(0x2722);
277
278       prints "FOUR TEARDROP-SPOKED ASTERISK".
279
280       The name returned is the "best" (defined below) official name or alias
281       for the code point, if available; otherwise your custom alias for it,
282       if defined; otherwise "undef".  This means that your alias will only be
283       returned for code points that don't have an official Unicode name (nor
284       alias) such as private use code points.
285
286       If you define more than one name for the code point, it is
287       indeterminate which one will be returned.
288
289       As mentioned, the function returns "undef" if no name is known for the
290       code point.  In Unicode the proper name for these is the empty string,
291       which "undef" stringifies to.  (If you ask for a code point past the
292       legal Unicode maximum of U+10FFFF that you haven't assigned an alias
293       to, you get "undef" plus a warning.)
294
295       The input number must be a non-negative integer, or a string beginning
296       with "U+" or "0x" with the remainder considered to be a hexadecimal
297       integer.  A literal numeric constant must be unsigned; it will be
298       interpreted as hex if it has a leading zero or contains non-decimal hex
299       digits; otherwise it will be interpreted as decimal.  If it begins with
300       "U+", it is interpreted as the Unicode code point; otherwise it is
301       interpreted as native.  (Only code points below 256 can differ between
302       Unicode and native.)  Thus "U+41" is always the Latin letter "A"; but
303       0x41 can be "NO-BREAK SPACE" on EBCDIC platforms.
304
305       As mentioned above under "ALIASES", Unicode 6.1 defines extra names
306       (synonyms or aliases) for some code points, most of which were already
307       available as Perl extensions.  All these are accepted by "\N{...}" and
308       the other functions in this module, but "viacode" has to choose which
309       one name to return for a given input code point, so it returns the
310       "best" name.  To understand how this works, it is helpful to know more
311       about the Unicode name properties.  All code points actually have only
312       a single name, which (starting in Unicode 2.0) can never change once a
313       character has been assigned to the code point.  But mistakes have been
314       made in assigning names, for example sometimes a clerical error was
315       made during the publishing of the Standard which caused words to be
316       misspelled, and there was no way to correct those.  The Name_Alias
317       property was eventually created to handle these situations.  If a name
318       was wrong, a corrected synonym would be published for it, using
319       Name_Alias.  "viacode" will return that corrected synonym as the "best"
320       name for a code point.  (It is even possible, though it hasn't happened
321       yet, that the correction itself will need to be corrected, and so
322       another Name_Alias can be created for that code point; "viacode" will
323       return the most recent correction.)
324
325       The Unicode name for each of the control characters (such as LINE FEED)
326       is the empty string.  However almost all had names assigned by other
327       standards, such as the ASCII Standard, or were in common use.
328       "viacode" returns these names as the "best" ones available.  Unicode
329       6.1 has created Name_Aliases for each of them, including alternate
330       names, like NEW LINE.  "viacode" uses the original name, "LINE FEED" in
331       preference to the alternate.  Similarly the name returned for U+FEFF is
332       "ZERO WIDTH NO-BREAK SPACE", not "BYTE ORDER MARK".
333
334       Until Unicode 6.1, the 4 control characters U+0080, U+0081, U+0084, and
335       U+0099 did not have names nor aliases.  To preserve backwards
336       compatibility, any alias you define for these code points will be
337       returned by this function, in preference to the official name.
338
339       Some code points also have abbreviated names, such as "LF" or "NL".
340       "viacode" never returns these.
341
342       Because a name correction may be added in future Unicode releases, the
343       name that "viacode" returns may change as a result.  This is a rare
344       event, but it does happen.
345

CUSTOM TRANSLATORS

347       The mechanism of translation of "\N{...}" escapes is general and not
348       hardwired into charnames.pm.  A module can install custom translations
349       (inside the scope which "use"s the module) with the following magic
350       incantation:
351
352           sub import {
353               shift;
354               $^H{charnames} = \&translator;
355           }
356
357       Here translator() is a subroutine which takes CHARNAME as an argument,
358       and returns text to insert into the string instead of the
359       "\N{CHARNAME}" escape.
360
361       This is the only way you can create a custom named sequence of code
362       points.
363
364       Since the text to insert should be different in "bytes" mode and out of
365       it, the function should check the current state of "bytes"-flag as in:
366
367           use bytes ();                      # for $bytes::hint_bits
368           sub translator {
369               if ($^H & $bytes::hint_bits) {
370                   return bytes_translator(@_);
371               }
372               else {
373                   return utf8_translator(@_);
374               }
375           }
376
377       See "CUSTOM ALIASES" above for restrictions on CHARNAME.
378
379       Of course, "vianame", "viacode", and "string_vianame" would need to be
380       overridden as well.
381

BUGS

383       vianame() normally returns an ordinal code point, but when the input
384       name is of the form "U+...", it returns a chr instead.  In this case,
385       if "use bytes" is in effect and the character won't fit into a byte, it
386       returns "undef" and raises a warning.
387
388       Since evaluation of the translation function (see "CUSTOM TRANSLATORS")
389       happens in the middle of compilation (of a string literal), the
390       translation function should not do any "eval"s or "require"s.  This
391       restriction should be lifted (but is low priority) in a future version
392       of Perl.
393
394
395
396perl v5.30.2                      2020-03-27                    charnames(3pm)
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