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perl-5.13.3
River stage five • 11292 direct dependents • 32664 total dependents
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/ charnames

NAME

charnames - access to Unicode character names and define character names for \N{named} string literal escapes

SYNOPSIS

  use charnames ':full';
  print "\N{GREEK SMALL LETTER SIGMA} is called sigma.\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 charnames ":full", ":alias" => {
    e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
    mychar => 0xE8000,  # Private use area
  };
  print "\N{e_ACUTE} is a small letter e with an acute.\n";
  print "\\N{mychar} allows me to name private use characters.\n";

  use charnames ();
  print charnames::viacode(0x1234); # prints "ETHIOPIC SYLLABLE SEE"
  printf "%04X", charnames::vianame("GOTHIC LETTER AHSA"); # prints
                                                           # "10330"

DESCRIPTION

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

All forms of the pragma enable use of the "charnames::vianame(name)" function for run-time lookup of a character name to get its ordinal (code point), and the inverse function, "charnames::viacode(code)".

Forms other than "use charnames ();" enable the use of of \N{CHARNAME} sequences to compile a Unicode character into a string based on its name.

Note that \N{U+...}, where the ... is a hexadecimal number, also inserts a character into a string, but doesn't require the use of this pragma. The character it inserts is the one whose code point (ordinal value) is equal to the number. For example, "\N{U+263a}" is the Unicode (white background, black foreground) smiley face; it doesn't require this pragma, whereas the equivalent, "\N{WHITE SMILING FACE}" does. Also, \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, :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 of standard Unicode character names. If :short is present, and CHARNAME has the form SCRIPT:CNAME, then CNAME is looked up as a letter in script SCRIPT. If use charnames is used with script name arguments, then for \N{CHARNAME} the name CHARNAME 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 CHARNAME inside a given script SCRIPTNAME this pragma looks for the names

  SCRIPTNAME CAPITAL LETTER CHARNAME
  SCRIPTNAME SMALL LETTER CHARNAME
  SCRIPTNAME LETTER CHARNAME

in the table of standard Unicode names. If CHARNAME is lowercase, then the CAPITAL variant is ignored, otherwise the SMALL variant is ignored.

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 charnames::vianame().

For the C0 and C1 control characters (U+0000..U+001F, U+0080..U+009F) there are no official Unicode names but you can use instead the ISO 6429 names (LINE FEED, ESCAPE, and so forth, and their abbreviations, LF, ESC, ...). In Unicode 3.2 (as of Perl 5.8) some naming changes took place, and ISO 6429 was updated, see "ALIASES".

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

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{charname} or \N{U+code point} will automatically have Unicode semantics (see "Byte and Character Semantics" in perlunicode).

ALIASES

A few aliases have been defined for convenience: instead of having to use the official names

    LINE FEED (LF)
    FORM FEED (FF)
    CARRIAGE RETURN (CR)
    NEXT LINE (NEL)

(yes, with parentheses), one can use

    LINE FEED
    FORM FEED
    CARRIAGE RETURN
    NEXT LINE
    LF
    FF
    CR
    NEL

All the other standard abbreviations for the controls, such as ACK for ACKNOWLEDGE also can be used.

One can also use

    BYTE ORDER MARK
    BOM

and these abbreviations

    Abbreviation        Full Name

    CGJ                 COMBINING GRAPHEME JOINER
    FVS1                MONGOLIAN FREE VARIATION SELECTOR ONE
    FVS2                MONGOLIAN FREE VARIATION SELECTOR TWO
    FVS3                MONGOLIAN FREE VARIATION SELECTOR THREE
    LRE                 LEFT-TO-RIGHT EMBEDDING
    LRM                 LEFT-TO-RIGHT MARK
    LRO                 LEFT-TO-RIGHT OVERRIDE
    MMSP                MEDIUM MATHEMATICAL SPACE
    MVS                 MONGOLIAN VOWEL SEPARATOR
    NBSP                NO-BREAK SPACE
    NNBSP               NARROW NO-BREAK SPACE
    PDF                 POP DIRECTIONAL FORMATTING
    RLE                 RIGHT-TO-LEFT EMBEDDING
    RLM                 RIGHT-TO-LEFT MARK
    RLO                 RIGHT-TO-LEFT OVERRIDE
    SHY                 SOFT HYPHEN
    VS1                 VARIATION SELECTOR-1
    .
    .
    .
    VS256               VARIATION SELECTOR-256
    WJ                  WORD JOINER
    ZWJ                 ZERO WIDTH JOINER
    ZWNJ                ZERO WIDTH NON-JOINER
    ZWSP                ZERO WIDTH SPACE

For backward compatibility one can use the old names for certain C0 and C1 controls

    old                         new

    FILE SEPARATOR              INFORMATION SEPARATOR FOUR
    GROUP SEPARATOR             INFORMATION SEPARATOR THREE
    HORIZONTAL TABULATION       CHARACTER TABULATION
    HORIZONTAL TABULATION SET   CHARACTER TABULATION SET
    HORIZONTAL TABULATION WITH JUSTIFICATION    CHARACTER TABULATION
                                                WITH JUSTIFICATION
    PARTIAL LINE DOWN           PARTIAL LINE FORWARD
    PARTIAL LINE UP             PARTIAL LINE BACKWARD
    RECORD SEPARATOR            INFORMATION SEPARATOR TWO
    REVERSE INDEX               REVERSE LINE FEED
    UNIT SEPARATOR              INFORMATION SEPARATOR ONE
    VERTICAL TABULATION         LINE TABULATION
    VERTICAL TABULATION SET     LINE TABULATION SET

but the old names in addition to giving the character will also give a warning about being deprecated.

And finally, certain published variants are usable, including some for controls that have no Unicode names:

    name                                   character

    END OF PROTECTED AREA                  END OF GUARDED AREA, U+0097
    HIGH OCTET PRESET                      U+0081
    HOP                                    U+0081
    IND                                    U+0084
    INDEX                                  U+0084
    PAD                                    U+0080
    PADDING CHARACTER                      U+0080
    PRIVATE USE 1                          PRIVATE USE ONE, U+0091
    PRIVATE USE 2                          PRIVATE USE TWO, U+0092
    SGC                                    U+0099
    SINGLE GRAPHIC CHARACTER INTRODUCER    U+0099
    SINGLE-SHIFT 2                         SINGLE SHIFT TWO, U+008E
    SINGLE-SHIFT 3                         SINGLE SHIFT THREE, U+008F
    START OF PROTECTED AREA                START OF GUARDED AREA, U+0096

CUSTOM ALIASES

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.

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

An alias can map to either an official Unicode character 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. The number must look like an unsigned decimal integer, or a hexadecimal constant beginning with 0x, or U+.

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";

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";

charnames::viacode(code)

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 official name for the code point, if available, otherwise your custom alias for it. This means that your alias will only be returned for code points that don't have an official Unicode name (nor Unicode version 1 name), such as private use code points, and the 4 control characters U+0080, U+0081, U+0084, and U+0099. If you define more than one name for the code point, it is indeterminate which one will be returned.

The function returns undef if no name is known for the code point. In Unicode the proper name of 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 and a warning.)

Notice that the name returned for of U+FEFF is "ZERO WIDTH NO-BREAK SPACE", not "BYTE ORDER MARK".

charnames::vianame(name)

Returns the code point indicated by the name. For example,

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

prints "2722".

vianame takes the identical inputs that \N{...} does under the :full and :short options to the charnames pragma, including any custom aliases you may have defined.

There are just a few differences. The main one is that under most circumstances, (see "BUGS" for the other ones), vianame returns an ord, whereas \\N{...} is seamlessly placed as a chr into the string in which it appears. This leads to a second difference. Since an ord is returned, it can be that of any character, even one that isn't legal under the use bytes pragma. It is up to the caller to validate the return under use bytes before converting it to chr.

The final difference is that if the input name is unknown vianame returns undef instead of the REPLACEMENT CHARACTER, and it does not raise a warning message.

CUSTOM TRANSLATORS

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

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

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

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

BUGS

vianame returns a chr if the input name is of the form U+..., and an ord otherwise. It is proposed to change this to always return an ord. Send email to perl5-porters@perl.org to comment on this proposal. If use bytes is in effect when a chr is returned, and if that chr won't fit into a byte, undef is returned instead.

All the Hangul syllable characters are treated as having no names, as are almost all the CJK Unicode characters that have their code points as part of their names.

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

Unicode standard named sequences are not recognized, such as LATIN CAPITAL LETTER A WITH MACRON AND GRAVE (which should mean LATIN CAPITAL LETTER A WITH MACRON with an additional COMBINING GRAVE ACCENT).

Since evaluation of the translation function happens in the middle of compilation (of a string literal), the translation function should not do any evals or requires. This restriction should be lifted (but is low priority) in a future version of Perl.