charnames(3p) Perl Programmers Reference Guide charnames(3p)

charnames(3p) Perl Programmers Reference Guide charnames(3p) #

charnames(3p) Perl Programmers Reference Guide charnames(3p)

NNAAMMEE #

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

SSYYNNOOPPSSIISS #

  use charnames ':full';
  print "\N{GREEK SMALL LETTER SIGMA} is called sigma.\n";
  print "\N{LATIN CAPITAL LETTER E WITH VERTICAL LINE BELOW}",
        " is an officially named sequence of two Unicode characters\n";

  use charnames ':loose';
  print "\N{Greek small-letter  sigma}",
         "can be used to ignore case, underscores, most blanks,"
         "and when you aren't sure if the official name has hyphens\n";

  use charnames ':short';
  print "\N{greek:Sigma} is an upper-case sigma.\n";

  use charnames qw(cyrillic greek);
  print "\N{sigma} is Greek sigma, and \N{be} is Cyrillic b.\n";

  use utf8;
  use charnames ":full", ":alias" => {
    e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
    mychar => 0xE8000,  # Private use area

“自転車に乗る人” => “BICYCLIST” #

  };
  print "\N{e_ACUTE} is a small letter e with an acute.\n";
  print "\N{mychar} allows me to name private use characters.\n";
  print "And I can create synonyms in other languages,",
        " such as \N{自転車に乗る人} for "BICYCLIST (U+1F6B4)\n";

  use charnames ();
  print charnames::viacode(0x1234); # prints "ETHIOPIC SYLLABLE SEE"
  printf "%04X", charnames::vianame("GOTHIC LETTER AHSA"); # prints
                                                           # "10330"
  print charnames::vianame("LATIN CAPITAL LETTER A"); # prints 65 on
                                                      # ASCII platforms;
                                                      # 193 on EBCDIC
  print charnames::string_vianame("LATIN CAPITAL LETTER A"); # prints "A"

DDEESSCCRRIIPPTTIIOONN #

 Pragma "use charnames" is used to gain access to the names of the Unicode
 characters and named character sequences, and to allow you to define your
 own character and character sequence names.

 All forms of the pragma enable use of the following 3 functions:

 •   "charnames::string_vianame(_n_a_m_e)" for run-time lookup of a either a
     character name or a named character sequence, returning its string
     representation

 •   "charnames::vianame(_n_a_m_e)" for run-time lookup of a character name
     (but not a named character sequence) to get its ordinal value (code
     point)

 •   "charnames::viacode(_c_o_d_e)" for run-time lookup of a code point to get
     its Unicode name.

 Starting in Perl v5.16, any occurrence of "\N{_C_H_A_R_N_A_M_E}" sequences in a
 double-quotish string automatically loads this module with arguments
 ":full" and ":short" (described below) if it hasn't already been loaded
 with different arguments, in order to compile the named Unicode character
 into position in the string.  Prior to v5.16, an explicit "use charnames"
 was required to enable this usage.  (However, prior to v5.16, the form
 "use charnames ();" did not enable "\N{_C_H_A_R_N_A_M_E}".)

 Note that "\N{U+_._._.}", where the _._._. is a hexadecimal number, also
 inserts a character into a string.  The character it inserts is the one
 whose Unicode code point (ordinal value) is equal to the number.  For
 example, "\N{U+263a}" is the Unicode (white background, black foreground)
 smiley face equivalent to "\N{WHITE SMILING FACE}".  Also note, "\N{_._._.}"
 can mean a regex quantifier instead of a character name, when the _._._. is
 a number (or comma separated pair of numbers (see "QUANTIFIERS" in
 perlreref), and is not related to this pragma.

 The "charnames" pragma supports arguments ":full", ":loose", ":short",
 script names and customized aliases.

 If ":full" is present, for expansion of "\N{_C_H_A_R_N_A_M_E}", the string
 _C_H_A_R_N_A_M_E is first looked up in the list of standard Unicode character
 names.

 ":loose" is a variant of ":full" which allows _C_H_A_R_N_A_M_E to be less
 precisely specified.  Details are in "LOOSE MATCHES".

 If ":short" is present, and _C_H_A_R_N_A_M_E has the form "_S_C_R_I_P_T:_C_N_A_M_E", then
 _C_N_A_M_E is looked up as a letter in script _S_C_R_I_P_T, as described in the next
 paragraph.  Or, if "use charnames" is used with script name arguments,
 then for "\N{_C_H_A_R_N_A_M_E}" the name _C_H_A_R_N_A_M_E is looked up as a letter in the
 given scripts (in the specified order). Customized aliases can override
 these, and are explained in "CUSTOM ALIASES".

 For lookup of _C_H_A_R_N_A_M_E inside a given script _S_C_R_I_P_T_N_A_M_E, this pragma
 looks in the table of standard Unicode names for the names

SCRIPTNAME CAPITAL LETTER CHARNAME #

SCRIPTNAME SMALL LETTER CHARNAME #

SCRIPTNAME LETTER CHARNAME #

 If _C_H_A_R_N_A_M_E is all lowercase, then the "CAPITAL" variant is ignored,
 otherwise the "SMALL" variant is ignored, and both _C_H_A_R_N_A_M_E and
 _S_C_R_I_P_T_N_A_M_E are converted to all uppercase for look-up.  Other than that,
 both of them follow loose rules if ":loose" is also specified; strict
 otherwise.

 Note that "\N{...}" is compile-time; it's a special form of string
 constant used inside double-quotish strings; this means that you cannot
 use variables inside the "\N{...}".  If you want similar run-time
 functionality, use cchhaarrnnaammeess::::ssttrriinngg__vviiaannaammee(()).

 Note, starting in Perl 5.18, the name "BELL" refers to the Unicode
 character U+1F514, instead of the traditional U+0007.  For the latter,
 use "ALERT" or "BEL".

 It is a syntax error to use "\N{NAME}" where "NAME" is unknown.

 For "\N{NAME}", it is a fatal error if "use bytes" is in effect and the
 input name is that of a character that won't fit into a byte (i.e., whose
 ordinal is above 255).

 Otherwise, any string that includes a "\N{_c_h_a_r_n_a_m_e}" or
 "\N{U+_c_o_d_e_ _p_o_i_n_t}" will automatically have Unicode rules (see "Byte and
 Character Semantics" in perlunicode).

LLOOOOSSEE MMAATTCCHHEESS #

 By specifying ":loose", Unicode's loose character name matching
 <http://www.unicode.org/reports/tr44#Matching_Rules> rules are selected
 instead of the strict exact match used otherwise.  That means that
 _C_H_A_R_N_A_M_E doesn't have to be so precisely specified.  Upper/lower case
 doesn't matter (except with scripts as mentioned above), nor do any
 underscores, and the only hyphens that matter are those at the beginning
 or end of a word in the name (with one exception:  the hyphen in U+1180
 "HANGUL JUNGSEONG O-E" does matter).  Also, blanks not adjacent to
 hyphens don't matter.  The official Unicode names are quite variable as
 to where they use hyphens versus spaces to separate word-like units, and
 this option allows you to not have to care as much.  The reason non-
 medial hyphens matter is because of cases like U+0F60 "TIBETAN LETTER -A"
 versus U+0F68 "TIBETAN LETTER A".  The hyphen here is significant, as is
 the space before it, and so both must be included.

 ":loose" slows down look-ups by a factor of 2 to 3 versus ":full", but
 the trade-off may be worth it to you.  Each individual look-up takes very
 little time, and the results are cached, so the speed difference would
 become a factor only in programs that do look-ups of many different
 spellings, and probably only when those look-ups are through "vianame()"
 and "string_vianame()", since "\N{...}" look-ups are done at compile
 time.

AALLIIAASSEESS #

 Starting in Unicode 6.1 and Perl v5.16, Unicode defines many
 abbreviations and names that were formerly Perl extensions, and some
 additional ones that Perl did not previously accept.  The list is getting
 too long to reproduce here, but you can get the complete list from the
 Unicode web site:
 <http://www.unicode.org/Public/UNIDATA/NameAliases.txt>.

 Earlier versions of Perl accepted almost all the 6.1 names.  These were
 most extensively documented in the v5.14 version of this pod:
 <http://perldoc.perl.org/5.14.0/charnames.html#ALIASES>.

CCUUSSTTOOMM AALLIIAASSEESS #

 You can add customized aliases to standard (":full") Unicode naming
 conventions.  The aliases override any standard definitions, so, if
 you're twisted enough, you can change "\N{LATIN CAPITAL LETTER A}" to
 mean "B", etc.

 Aliases must begin with a character that is alphabetic.  After that, each
 may contain any combination of word ("\w") characters, SPACE (U+0020),
 HYPHEN-MINUS (U+002D), LEFT PARENTHESIS (U+0028), and RIGHT PARENTHESIS
 (U+0029).  These last two should never have been allowed in names, and
 are retained for backwards compatibility only, and may be deprecated and
 removed in future releases of Perl, so don't use them for new names.
 (More precisely, the first character of a name you specify must be
 something that matches all of "\p{ID_Start}", "\p{Alphabetic}", and
 "\p{Gc=Letter}".  This makes sure it is what any reasonable person would
 view as an alphabetic character.  And, the continuation characters that
 match "\w" must also match "\p{ID_Continue}".)  Starting with Perl v5.18,
 any Unicode characters meeting the above criteria may be used; prior to
 that only Latin1-range characters were acceptable.

 An alias can map to either an official Unicode character name (not a
 loose matched name) or to a numeric code point (ordinal).  The latter is
 useful for assigning names to code points in Unicode private use areas
 such as U+E800 through U+F8FF.  A numeric code point must be a non-
 negative integer, or a string beginning with "U+" or "0x" with the
 remainder considered to be a hexadecimal integer.  A literal numeric
 constant must be unsigned; it will be interpreted as hex if it has a
 leading zero or contains non-decimal hex digits; otherwise it will be
 interpreted as decimal.  If it begins with "U+", it is interpreted as the
 Unicode code point; otherwise it is interpreted as native.  (Only code
 points below 256 can differ between Unicode and native.)  Thus "U+41" is
 always the Latin letter "A"; but 0x41 can be "NO-BREAK SPACE" on EBCDIC
 platforms.

 Aliases are added either by the use of anonymous hashes:

     use charnames ":alias" => {
         e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
         mychar1 => 0xE8000,
         };
     my $str = "\N{e_ACUTE}";

 or by using a file containing aliases:

     use charnames ":alias" => "pro";

 This will try to read "unicore/pro_alias.pl" from the @INC path. This
 file should return a list in plain perl:

     (

A_GRAVE => “LATIN CAPITAL LETTER A WITH GRAVE”, #

A_CIRCUM => “LATIN CAPITAL LETTER A WITH CIRCUMFLEX”, #

A_DIAERES => “LATIN CAPITAL LETTER A WITH DIAERESIS”, #

A_TILDE => “LATIN CAPITAL LETTER A WITH TILDE”, #

A_BREVE => “LATIN CAPITAL LETTER A WITH BREVE”, #

A_RING => “LATIN CAPITAL LETTER A WITH RING ABOVE”, #

A_MACRON => “LATIN CAPITAL LETTER A WITH MACRON”, #

     mychar2         => "U+E8001",
     );

 Both these methods insert ":full" automatically as the first argument (if
 no other argument is given), and you can give the ":full" explicitly as
 well, like

     use charnames ":full", ":alias" => "pro";

 ":loose" has no effect with these.  Input names must match exactly, using
 ":full" rules.

 Also, both these methods currently allow only single characters to be
 named.  To name a sequence of characters, use a custom translator
 (described below).

cchhaarrnnaammeess::::ssttrriinngg__vviiaannaammee((_n_a_m_e)) This is a runtime equivalent to “\N{…}”. _n_a_m_e can be any expression that evaluates to a name accepted by “\N{…}” under the “:full” option to “charnames”. In addition, any other options for the controlling “use charnames” in the same scope apply, like “:loose” or any script list, “:short” option, or custom aliases you may have defined.

 The only differences are due to the fact that "string_vianame" is run-
 time and "\N{}" is compile time.  You can't interpolate inside a "\N{}",
 (so "\N{$variable}" doesn't work); and if the input name is unknown,
 "string_vianame" returns "undef" instead of it being a syntax error.

cchhaarrnnaammeess::::vviiaannaammee((_n_a_m_e)) This is similar to “string_vianame”. The main difference is that under most circumstances, “vianame” returns an ordinal code point, whereas “string_vianame” returns a string. For example,

    printf "U+%04X", charnames::vianame("FOUR TEARDROP-SPOKED ASTERISK");

 prints "U+2722".

 This leads to the other two differences.  Since a single code point is
 returned, the function can't handle named character sequences, as these
 are composed of multiple characters (it returns "undef" for these.  And,
 the code point can be that of any character, even ones that aren't legal
 under the "use bytes" pragma,

 See "BUGS" for the circumstances in which the behavior differs from  that
 described above.

cchhaarrnnaammeess::::vviiaaccooddee((_c_o_d_e)) Returns the full name of the character indicated by the numeric code. For example,

     print charnames::viacode(0x2722);

 prints "FOUR TEARDROP-SPOKED ASTERISK".

 The name returned is the "best" (defined below) official name or alias
 for the code point, if available; otherwise your custom alias for it, if
 defined; otherwise "undef".  This means that your alias will only be
 returned for code points that don't have an official Unicode name (nor
 alias) such as private use code points.

 If you define more than one name for the code point, it is indeterminate
 which one will be returned.

 As mentioned, the function returns "undef" if no name is known for the
 code point.  In Unicode the proper name for these is the empty string,
 which "undef" stringifies to.  (If you ask for a code point past the
 legal Unicode maximum of U+10FFFF that you haven't assigned an alias to,
 you get "undef" plus a warning.)

 The input number must be a non-negative integer, or a string beginning
 with "U+" or "0x" with the remainder considered to be a hexadecimal
 integer.  A literal numeric constant must be unsigned; it will be
 interpreted as hex if it has a leading zero or contains non-decimal hex
 digits; otherwise it will be interpreted as decimal.  If it begins with
 "U+", it is interpreted as the Unicode code point; otherwise it is
 interpreted as native.  (Only code points below 256 can differ between
 Unicode and native.)  Thus "U+41" is always the Latin letter "A"; but
 0x41 can be "NO-BREAK SPACE" on EBCDIC platforms.

 As mentioned above under "ALIASES", Unicode 6.1 defines extra names
 (synonyms or aliases) for some code points, most of which were already
 available as Perl extensions.  All these are accepted by "\N{...}" and
 the other functions in this module, but "viacode" has to choose which one
 name to return for a given input code point, so it returns the "best"
 name.  To understand how this works, it is helpful to know more about the
 Unicode name properties.  All code points actually have only a single
 name, which (starting in Unicode 2.0) can never change once a character
 has been assigned to the code point.  But mistakes have been made in
 assigning names, for example sometimes a clerical error was made during
 the publishing of the Standard which caused words to be misspelled, and
 there was no way to correct those.  The Name_Alias property was
 eventually created to handle these situations.  If a name was wrong, a
 corrected synonym would be published for it, using Name_Alias.  "viacode"
 will return that corrected synonym as the "best" name for a code point.
 (It is even possible, though it hasn't happened yet, that the correction
 itself will need to be corrected, and so another Name_Alias can be
 created for that code point; "viacode" will return the most recent
 correction.)

 The Unicode name for each of the control characters (such as LINE FEED)
 is the empty string.  However almost all had names assigned by other
 standards, such as the ASCII Standard, or were in common use.  "viacode"
 returns these names as the "best" ones available.  Unicode 6.1 has
 created Name_Aliases for each of them, including alternate names, like
 NEW LINE.  "viacode" uses the original name, "LINE FEED" in preference to
 the alternate.  Similarly the name returned for U+FEFF is "ZERO WIDTH NO-
 BREAK SPACE", not "BYTE ORDER MARK".

 Until Unicode 6.1, the 4 control characters U+0080, U+0081, U+0084, and
 U+0099 did not have names nor aliases.  To preserve backwards
 compatibility, any alias you define for these code points will be
 returned by this function, in preference to the official name.

 Some code points also have abbreviated names, such as "LF" or "NL".
 "viacode" never returns these.

 Because a name correction may be added in future Unicode releases, the
 name that "viacode" returns may change as a result.  This is a rare
 event, but it does happen.

CCUUSSTTOOMM TTRRAANNSSLLAATTOORRSS #

 The mechanism of translation of "\N{...}" escapes is general and not
 hardwired into _c_h_a_r_n_a_m_e_s_._p_m.  A module can install custom translations
 (inside the scope which "use"s the module) with the following magic
 incantation:

     sub import {
         shift;
         $^H{charnames} = \&translator;
     }

 Here ttrraannssllaattoorr(()) is a subroutine which takes _C_H_A_R_N_A_M_E as an argument,
 and returns text to insert into the string instead of the "\N{_C_H_A_R_N_A_M_E}"
 escape.

 This is the only way you can create a custom named sequence of code
 points.

 Since the text to insert should be different in "bytes" mode and out of
 it, the function should check the current state of "bytes"-flag as in:

     use bytes ();                      # for $bytes::hint_bits
     sub translator {
         if ($^H & $bytes::hint_bits) {
             return bytes_translator(@_);
         }
         else {
             return utf8_translator(@_);
         }
     }

 See "CUSTOM ALIASES" above for restrictions on _C_H_A_R_N_A_M_E.

 Of course, "vianame", "viacode", and "string_vianame" would need to be
 overridden as well.

BBUUGGSS #

 vviiaannaammee(()) normally returns an ordinal code point, but when the input name
 is of the form "U+...", it returns a chr instead.  In this case, if "use
 bytes" is in effect and the character won't fit into a byte, it returns
 "undef" and raises a warning.

 Since evaluation of the translation function (see "CUSTOM TRANSLATORS")
 happens in the middle of compilation (of a string literal), the
 translation function should not do any "eval"s or "require"s.  This
 restriction should be lifted (but is low priority) in a future version of
 Perl.

perl v5.36.3 2023-02-15 charnames(3p)