charnames(3pm) Perl Programmers Reference Guide charnames(3pm)
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.\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
"XXXXXXX" => "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{XXXXXXX} 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"
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.
Starting in Perl v5.16, any occurrence of "\N{CHARNAME}" 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{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 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{CHARNAME}", the string
CHARNAME is first looked up in the list of standard Unicode character
names.
":loose" is a variant of ":full" which allows CHARNAME to be less
precisely specified. Details are in "LOOSE MATCHES".
If ":short" is present, and CHARNAME has the form "SCRIPT:CNAME", then
CNAME is looked up as a letter in script SCRIPT, as described in the
next paragraph. Or, 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 in the table of standard Unicode names for the names
SCRIPTNAME CAPITAL LETTER CHARNAME
SCRIPTNAME SMALL LETTER CHARNAME
SCRIPTNAME LETTER CHARNAME
If CHARNAME is all lowercase, then the "CAPITAL" variant is ignored,
otherwise the "SMALL" variant is ignored, and both CHARNAME and
SCRIPTNAME 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 charnames::string_vianame().
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{charname}" or
"\N{U+code point}" will automatically have Unicode rules (see "Byte and
Character Semantics" in perlunicode).
LOOSE MATCHES
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
CHARNAME 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.
ALIASES
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>;.
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.
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 $str = "\N{e_ACUTE}";
or by using a file containing aliases:
use charnames ":alias" => "pro";
This will try to read "unicore/pro_alias.pl" from the @INC path. This
file should return a list in plain perl:
(
A_GRAVE => "LATIN CAPITAL LETTER A WITH GRAVE",
A_CIRCUM => "LATIN CAPITAL LETTER A WITH CIRCUMFLEX",
A_DIAERES => "LATIN CAPITAL LETTER A WITH DIAERESIS",
A_TILDE => "LATIN CAPITAL LETTER A WITH TILDE",
A_BREVE => "LATIN CAPITAL LETTER A WITH BREVE",
A_RING => "LATIN CAPITAL LETTER A WITH RING ABOVE",
A_MACRON => "LATIN CAPITAL LETTER A WITH MACRON",
mychar2 => "U+E8001",
);
Both these methods insert ":full" automatically as the first argument
(if no other argument is given), and you can give the ":full"
explicitly as well, like
use charnames ":full", ":alias" => "pro";
":loose" has no effect with these. Input names must match exactly,
using ":full" rules.
Also, both these methods currently allow only single characters to be
named. To name a sequence of characters, use a custom translator
(described below).
charnames::string_vianame(name)
This is a runtime equivalent to "\N{...}". name can be any expression
that evaluates to a name accepted by "\N{...}" under the ":full" option
to "charnames". In addition, any other options for the controlling
"use charnames" in the same scope apply, like ":loose" or any script
list, ":short" option, or custom aliases you may have defined.
The only differences are due to the fact that "string_vianame" is run-
time and "\N{}" is compile time. You can't interpolate inside a
"\N{}", (so "\N{$variable}" doesn't work); and if the input name is
unknown, "string_vianame" returns "undef" instead of it being a syntax
error.
charnames::vianame(name)
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.
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 "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.
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.
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 CHARNAME.
Of course, "vianame", "viacode", and "string_vianame" 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.
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 v5.26.3 2018-03-23 charnames(3pm)
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