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Pragmas

Access to Unicode character names and named character sequences; also define chara

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NAME

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

SYNOPSIS

  1.  use charnames ':full';
    2.  
  2.  print "\N{GREEK SMALL LETTER SIGMA} is called sigma.\n";
    3.  
  3.  print "\N{LATIN CAPITAL LETTER E WITH VERTICAL LINE BELOW}",
    4.  
  4.    " is an officially named sequence of two Unicode characters\n";
    5.  
  5.  
  6.  use charnames ':loose';
    7.  
  7.  print "\N{Greek small-letter  sigma}",
    8.  
  8.  "can be used to ignore case, underscores, most blanks,"
    9.  
  9.  "and when you aren't sure if the official name has hyphens\n";
    10.  
  10.  
  11.  use charnames ':short';
    12.  
  12.  print "\N{greek:Sigma} is an upper-case sigma.\n";
    13.  
  13.  
  14.  use charnames qw(cyrillic greek);
    15.  
  15.  print "\N{sigma} is Greek sigma, and \N{be} is Cyrillic b.\n";
    16.  
  16.  
  17.  use charnames ":full", ":alias" => {
    18.  
  18.    e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
    19.  
  19.    mychar => 0xE8000,  # Private use area
    20.  
  20.  };
    21.  
  21.  print "\N{e_ACUTE} is a small letter e with an acute.\n";
    22.  
  22.  print "\N{mychar} allows me to name private use characters.\n";
    23.  
  23.  
  24.  use charnames ();
    25.  
  25.  print charnames::viacode(0x1234); # prints "ETHIOPIC SYLLABLE SEE"
    26.  
  26.  printf "%04X", charnames::vianame("GOTHIC LETTER AHSA"); # prints
    27.  
  27.   # "10330"
    28.  
  28.  print charnames::vianame("LATIN CAPITAL LETTER A"); # prints 65 on
    29.  
  29.  # ASCII platforms;
    30.  
  30.  # 193 on EBCDIC
    31.  
  31.  print charnames::string_vianame("LATIN CAPITAL LETTER A"); # prints "A"
    32.

DESCRIPTION

Pragma use charnames is used to gain access to the names of theUnicode characters and named character sequences, and to allow you to defineyour own character and character sequence names.

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

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

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 code point(ordinal value) is equal to the number. For example, "\N{U+263a}" isthe Unicode (white background, black foreground) smiley faceequivalent to "\N{WHITE SMILING FACE}".Also note, \N{...} can mean a regex quantifier instead of a charactername, 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{CHARNAME}, the string CHARNAME is first looked up in the list ofstandard Unicode character names.

:loose is a variant of :full which allows CHARNAME to be lessprecisely specified. Details are in LOOSE MATCHES.

If :short is present, andCHARNAME has the form SCRIPT:CNAME, then CNAME is looked upas a letter in script SCRIPT, as described in the next paragraph.Or, if use charnames is usedwith script name arguments, then for \N{CHARNAME} the nameCHARNAME is looked up as a letter in the given scripts (in thespecified order). Customized aliases can override these, and are explained inCUSTOM ALIASES.

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

  1.   SCRIPTNAME CAPITAL LETTER CHARNAME
    2.  
  2.   SCRIPTNAME SMALL LETTER CHARNAME
    3.  
  3.   SCRIPTNAME LETTER CHARNAME
    4.

If CHARNAME is all lowercase,then the CAPITAL variant is ignored, otherwise the SMALL variantis ignored, and both CHARNAME and SCRIPTNAME are converted to alluppercase 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 stringconstant used inside double-quotish strings; this means that you cannotuse variables inside the \N{...}. If you want similar run-timefunctionality, usecharnames::string_vianame().

Since Unicode 6.0, it is deprecated to use BELL. Instead use ALERT (butBEL will continue to work).

If the input name is unknown, \N{NAME} raises a warning andsubstitutes the Unicode REPLACEMENT CHARACTER (U+FFFD).

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

Otherwise, any string that includes a \N{charname} or\N{U+code point} will automatically have Unicode semantics (seeByte and Character Semantics in perlunicode).

LOOSE MATCHES

By specifying :loose, Unicode's loose character name matching rules areselected instead of the strict exact match used otherwise.That means that CHARNAME doesn't have to be so precisely specified.Upper/lower case doesn't matter (except with scripts as mentioned above), nordo any underscores, and the only hyphens that matter are those at thebeginning or end of a word in the name (with one exception: the hyphen inU+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 hyphensversus spaces to separate word-like units, and this option allows you to nothave to care as much.The reason non-medial hyphens matter is because of cases likeU+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 beincluded.

: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-uptakes very little time, and the results are cached, so the speed differencewould become a factor only in programs that do look-ups of many differentspellings, and probably only when those look-ups are through vianame() andstring_vianame(), since \N{...} look-ups are done at compile time.

ALIASES

Starting in Unicode 6.1 and Perl v5.16, Unicode defines many abbreviations andnames that were formerly Perl extensions, and some additional ones that Perldid 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 mostextensively documented in the v5.14 version of this pod:http://perldoc.perl.org/5.14.0/charnames.html#ALIASES.

CUSTOM ALIASES

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

Note that an alias should not be something that is a legal curlybrace-enclosed quantifier (see QUANTIFIERS in perlreref). For example\N{123} means to match 123 non-newline characters, and is not treated as acharnames alias. Aliases are discouraged from beginning with anythingother than an alphabetic character and from containing anything otherthan alphanumerics, spaces, dashes, parentheses, and underscores.Currently they must be ASCII.

An alias can map to either an official Unicode character name (not a loosematched name) or to anumeric code point (ordinal). The latter is useful for assigning namesto code points in Unicode private use areas such as U+E800 throughU+F8FF.A numeric code point must be a non-negative integer or a string beginningwith "U+" or "0x" with the remainder considered to be ahexadecimal integer. A literal numeric constant must be unsigned; itwill be interpreted as hex if it has a leading zero or containsnon-decimal hex digits; otherwise it will be interpreted as decimal.

Aliases are added either by the use of anonymous hashes:

  1.  use charnames ":alias" => {
    2.  
  2.  e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
    3.  
  3.  mychar1 => 0xE8000,
    4.  
  4.  };
    5.  
  5.  my $str = "\N{e_ACUTE}";
    6.

or by using a file containing aliases:

  1.  use charnames ":alias" => "pro";
    2.

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

  1.  (
    2.  
  2.  A_GRAVE => "LATIN CAPITAL LETTER A WITH GRAVE",
    3.  
  3.  A_CIRCUM => "LATIN CAPITAL LETTER A WITH CIRCUMFLEX",
    4.  
  4.  A_DIAERES   => "LATIN CAPITAL LETTER A WITH DIAERESIS",
    5.  
  5.  A_TILDE => "LATIN CAPITAL LETTER A WITH TILDE",
    6.  
  6.  A_BREVE => "LATIN CAPITAL LETTER A WITH BREVE",
    7.  
  7.  A_RING  => "LATIN CAPITAL LETTER A WITH RING ABOVE",
    8.  
  8.  A_MACRON => "LATIN CAPITAL LETTER A WITH MACRON",
    9.  
  9.  mychar2 => "U+E8001",
    10.  
  10.  );
    11.

Both these methods insert ":full" automatically as the first argument (if noother argument is given), and you can give the ":full" explicitly aswell, like

  1.  use charnames ":full", ":alias" => "pro";
    2.

":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 acustom translator (described below).

charnames::string_vianame(name)

This is a runtime equivalent to \N{...}. name can be any expressionthat evaluates to a name accepted by \N{...} under the :full option to charnames. In addition, any other options for thecontrolling "use charnames" in the same scope apply, like :loose or anyscript list, :short option, or custom aliases you may have defined.

The only difference is that if the input name is unknown, string_vianamereturns undef instead of the REPLACEMENT CHARACTER and does not raise awarning message.

charnames::vianame(name)

This is similar to string_vianame. The main difference is that under mostcircumstances, vianame returns an ordinal codepoint, whereas string_vianame returns a string. For example,

  1.    printf "U+%04X", charnames::vianame("FOUR TEARDROP-SPOKED ASTERISK");
    2.

prints "U+2722".

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

See BUGS for the circumstances in which the behavior differsfrom that described above.

charnames::viacode(code)

Returns the full name of the character indicated by the numeric code.For example,

  1.  print charnames::viacode(0x2722);
    2.

prints "FOUR TEARDROP-SPOKED ASTERISK".

The name returned is the "best" (defined below) official name or aliasfor the code point, ifavailable; otherwise your custom alias for it, if defined; otherwise undef.This means that your alias will only be returned for code points that don'thave 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 indeterminatewhich one will be returned.

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

The input number must be a non-negative integer, or a string beginningwith "U+" or "0x" with the remainder considered to be ahexadecimal integer. A literal numeric constant must be unsigned; itwill be interpreted as hex if it has a leading zero or containsnon-decimal hex digits; otherwise it will be interpreted as decimal.

As mentioned above under ALIASES, Unicode 6.1 defines extra names(synonyms or aliases) for some code points, most of which were alreadyavailable as Perl extensions. All these are accepted by \N{...} and theother functions in this module, but viacode has to choose which onename 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 Unicodename properties. All code points actually have only a single name, which(starting in Unicode 2.0) can never change once a character has been assignedto the code point. But mistakes have been made in assigning names, forexample sometimes a clerical error was made during the publishing of theStandard which caused words to be misspelled, and there was no way to correctthose. The Name_Alias property was eventually created to handle thesesituations. If a name was wrong, a corrected synonym would be published forit, 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 happenedyet, that the correction itself will need to be corrected, and so anotherName_Alias can be created for that code point; viacode will return themost recent correction.)

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

Until Unicode 6.1, the 4 control characters U+0080, U+0081, U+0084, and U+0099did not have names nor aliases.To preserve backwards compatibility, any alias you define for these codepoints 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 namethat viacode returns may change as a result. This is a rare event, but itdoes happen.

CUSTOM TRANSLATORS

The mechanism of translation of \N{...} escapes is general and nothardwired into charnames.pm. A module can install customtranslations (inside the scope which uses the module) with thefollowing magic incantation:

  1.  sub import {
    2.  
  2.  shift;
    3.  
  3.  $^H{charnames} = \&translator;
    4.  
  4.  }
    5.

Here translator() is a subroutine which takes CHARNAME as anargument, and returns text to insert into the string instead of the\N{CHARNAME} escape.

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

Since the text to insert should be differentin bytes mode and out of it, the function should check the currentstate of bytes-flag as in:

  1.  use bytes ();  # for $bytes::hint_bits
    2.  
  2.  sub translator {
    3.  
  3.  if ($^H & $bytes::hint_bits) {
    4.  
  4.  return bytes_translator(@_);
    5.  
  5.  }
    6.  
  6.  else {
    7.  
  7.  return utf8_translator(@_);
    8.  
  8.  }
    9.  
  9.  }
    10.

See CUSTOM ALIASES above for restrictions on CHARNAME.

Of course, vianame, viacode, and string_vianame would need to beoverridden as well.

BUGS

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

Names must be ASCII characters only, which means that you are out of luck ifyou want to create aliases in a language where some or all the characters ofthe desired aliases are non-ASCII.

Since evaluation of the translation function (see CUSTOM TRANSLATORS) happens in the middle of compilation (of a stringliteral), the translation function should not do any evals orrequires. This restriction should be lifted (but is low priority) ina future version of Perl.

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