charnames(3perl) Perl Programmers Reference Guide charnames(3perl)
NAME
charnames - access to Unicode character names and named character sequences; also define character names
SYNOPSIS
use charnames ':full';
print "N{GREEK SMALL LETTER SIGMA} is called sigma.
";
print "N{LATIN CAPITAL LETTER E WITH VERTICAL LINE BELOW}",
" is an officially named sequence of two Unicode characters
";
use charnames ':short';
print "N{greek:Sigma} is an upper-case sigma.
";
use charnames qw(cyrillic greek);
print "N{sigma} is Greek sigma, and N{be} is Cyrillic b.
";
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.
";
print "\N{mychar} allows me to name private use characters.
";
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"
DESCRIPTION
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:
o "charnames::string_vianame(name)" for run-time lookup of a either a character name or a named character sequence, returning its string
representation
o "charnames::vianame(name)" for run-time lookup of a character name (but not a named character sequence) to get its ordinal value (code
point)
o "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).
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. 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:
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";
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).
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" 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".
charnames::string_vianame(name)
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.
charnames::vianame(name)
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,
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 "use"s 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 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 "eval"s or "require"s. This restriction should be lifted (but is low priority) in a future version
of Perl.
perl v5.14.2 2011-09-26 charnames(3perl)