charnames - access to Unicode character names and named character sequences; also define character names
- 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 ':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"
- 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"
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(name) for run-time lookup of a either a character name or a named character sequence, returning its string representation
charnames::vianame(name) for run-time lookup of a character name (but not a named character sequence) to get its ordinal value (code point)
charnames::viacode(code) for run-time lookup of a code point to get its Unicode name.
All forms other than "use charnames ();"
also enable the use 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::string_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).
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{charname} or
\N{U+code point} will automatically have Unicode semantics (see
Byte and Character Semantics in perlunicode).
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
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.
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.
Aliases are added either by the use of anonymous hashes:
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";
Also, both these methods currently allow only a single character to be named. To name a sequence of characters, use a custom translator (described below).
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 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.
Notice that the name returned for of U+FEFF is "ZERO WIDTH NO-BREAK SPACE", not "BYTE ORDER MARK".
This is a runtime equivalent to \N{...}
. name 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 any script list, :short option, or custom aliases you
may have defined.
The only difference is that if the input name is unknown, string_vianame
returns undef instead of the REPLACEMENT CHARACTER and does not raise a
warning message.
This is similar to string_vianame
. The main difference is that under most
circumstances (see BUGS for the others), 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. And, the code point can be that of any
character, even ones that aren't legal under the use bytes
pragma,
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:
See CUSTOM ALIASES above for restrictions on CHARNAME.
Of course, vianame
and viacode
would need to be overridden as
well.
vianame 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.
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.
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 evals or
requires. This restriction should be lifted (but is low priority) in
a future version of Perl.