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Unicode::Collate(3)
NAME
Unicode::Collate - Unicode Collation Algorithm
SYNOPSIS
use Unicode::Collate;
#construct
$Collator = Unicode::Collate->new(%tailoring);
#sort
@sorted = $Collator->sort(@not_sorted);
#compare
$result = $Collator->cmp($a, $b); # returns 1, 0, or -1.
DESCRIPTION
Constructor and Tailoring
The "new" method returns a collator object.
$Collator = Unicode::Collate->new(
alternate => $alternate,
backwards => $levelNumber, # or \@levelNumbers
entry => $element,
normalization => $normalization_form,
ignoreName => qr/$ignoreName/,
ignoreChar => qr/$ignoreChar/,
katakana_before_hiragana => $bool,
level => $collationLevel,
overrideCJK => <!>overrideCJK,
overrideHangul => <!>overrideHangul,
preprocess => <!>preprocess,
rearrange => \@charList,
table => $filename,
undefName => qr/$undefName/,
undefChar => qr/$undefChar/,
upper_before_lower => $bool,
);
# if %tailoring is false (i.e. empty),
# $Collator should do the default collation.
alternate
-- see 3.2.2 Alternate Weighting, UTR #10.
This key allows to alternate weighting for variable collation elements,
which are marked with an ASTERISK in the table (NOTE: Many punction
marks and symbols are variable in allkeys.txt).
alternate => 'blanked', 'non-ignorable', 'shifted', or 'shift-trimmed'.
These names are case-insensitive. By default (if specification is
omitted), 'shifted' is adopted.
'Blanked' Variable elements are ignorable at levels 1 through 3;
considered at the 4th level.
'Non-ignorable' Variable elements are not reset to ignorable.
'Shifted' Variable elements are ignorable at levels 1 through 3
their level 4 weight is replaced by the old level 1 weight.
Level 4 weight for Non-Variable elements is 0xFFFF.
'Shift-Trimmed' Same as 'shifted', but all FFFF's at the 4th level
are trimmed.
backwards
-- see 3.1.2 French Accents, UTR #10.
backwards => $levelNumber or \@levelNumbers
Weights in reverse order; ex. level 2 (diacritic ordering) in French.
If omitted, forwards at all the levels.
entry
-- see 3.1 Linguistic Features; 3.2.1 File Format, UTR #10.
Overrides a default order or defines additional collation elements
entry => <<'ENTRIES', # use the UCA file format
00E6 ; [.0861.0020.0002.00E6] [.08B1.0020.0002.00E6] # ligature <ae> as <a><e>
0063 0068 ; [.0893.0020.0002.0063] # "ch" in traditional Spanish
0043 0068 ; [.0893.0020.0008.0043] # "Ch" in traditional Spanish
ENTRIES
ignoreName
ignoreChar
-- see Completely Ignorable, 3.2.2 Alternate Weighting, UTR #10.
Makes the entry in the table ignorable. If a collation element is
ignorable, it is ignored as if the element had been deleted from there.
E.g. when 'a' and 'e' are ignorable, 'element' is equal to 'lament' (or
'lmnt').
level
-- see 4.3 Form a sort key for each string, UTR #10.
Set the maximum level. Any higher levels than the specified one are
ignored.
Level 1: alphabetic ordering
Level 2: diacritic ordering
Level 3: case ordering
Level 4: tie-breaking (e.g. in the case when alternate is 'shifted')
ex.level => 2,
If omitted, the maximum is the 4th.
normalization
-- see 4.1 Normalize each input string, UTR #10.
If specified, strings are normalized before preparation of sort keys
(the normalization is executed after preprocess).
As a form name, one of the following names must be used.
'C' or 'NFC' for Normalization Form C
'D' or 'NFD' for Normalization Form D
'KC' or 'NFKC' for Normalization Form KC
'KD' or 'NFKD' for Normalization Form KD
If omitted, the string is put into Normalization Form D.
If "undef" is passed explicitly as the value for this key, any
normalization is not carried out (this may make tailoring easier if any
normalization is not desired).
see CAVEAT.
overrideCJK
-- see 7.1 Derived Collation Elements, UTR #10.
By default, mapping of CJK Unified Ideographs uses the Unicode
codepoint order. But the mapping of CJK Unified Ideographs may be
overrided.
ex. CJK Unified Ideographs in the JIS code point order.
overrideCJK => sub {
my $u = shift; # get a Unicode codepoint
my $b = pack('n', $u); # to UTF-16BE
my $s = your_unicode_to_sjis_converter($b); # convert
my $n = unpack('n', $s); # convert sjis to short
[ $n, 0x20, 0x2, $u ]; # return the collation element
},
ex. ignores all CJK Unified Ideographs.
overrideCJK => sub {()}, # CODEREF returning empty list
# where ->eq("Pe\x{4E00}rl", "Perl") is true
# as U+4E00 is a CJK Unified Ideograph and to be ignorable.
If "undef" is passed explicitly as the value for this key, weights for
CJK Unified Ideographs are treated as undefined. But assignment of
weight for CJK Unified Ideographs in table or entry is still valid.
overrideHangul
-- see 7.1 Derived Collation Elements, UTR #10.
By default, Hangul Syllables are decomposed into Hangul Jamo. But the
mapping of Hangul Syllables may be overrided.
This tag works like overrideCJK, so see there for examples.
If you want to override the mapping of Hangul Syllables, the
Normalization Forms D and KD are not appropriate (they will be
decomposed before overriding).
If "undef" is passed explicitly as the value for this key, weight for
Hangul Syllables is treated as undefined without decomposition into
Hangul Jamo. But definition of weight for Hangul Syllables in table or
entry is still valid.
preprocess
-- see 5.1 Preprocessing, UTR #10.
If specified, the coderef is used to preprocess before the formation of
sort keys.
ex. dropping English articles, such as "a" or "the". Then, "the pen"
is before "a pencil".
preprocess => sub {
my $str = shift;
$str =~ s/\b(?:an?|the)\s+//gi;
$str;
},
rearrange
-- see 3.1.3 Rearrangement, UTR #10.
Characters that are not coded in logical order and to be rearranged.
By default,
rearrange => [ 0x0E40..0x0E44, 0x0EC0..0x0EC4 ],
If you want to disallow any rearrangement, pass "undef" or "[]" (a
reference to an empty list) as the value for this key.
table
-- see 3.2 Default Unicode Collation Element Table, UTR #10.
You can use another element table if desired. The table file must be
in your "lib/Unicode/Collate" directory.
By default, the file "lib/Unicode/Collate/allkeys.txt" is used.
If "undef" is passed explicitly as the value for this key, no file is
read (but you can define collation elements via entry).
A typical way to define a collation element table without any file of
table:
$onlyABC = Unicode::Collate->new(
table => undef,
entry => << 'ENTRIES',
0061 ; [.0101.0020.0002.0061] # LATIN SMALL LETTER A
0041 ; [.0101.0020.0008.0041] # LATIN CAPITAL LETTER A
0062 ; [.0102.0020.0002.0062] # LATIN SMALL LETTER B
0042 ; [.0102.0020.0008.0042] # LATIN CAPITAL LETTER B
0063 ; [.0103.0020.0002.0063] # LATIN SMALL LETTER C
0043 ; [.0103.0020.0008.0043] # LATIN CAPITAL LETTER C
ENTRIES
);
undefName
undefChar
-- see 6.3.4 Reducing the Repertoire, UTR #10.
Undefines the collation element as if it were unassigned in the table.
This reduces the size of the table. If an unassigned character appears
in the string to be collated, the sort key is made from its codepoint
as a single-character collation element, as it is greater than any
other assigned collation elements (in the codepoint order among the
unassigned characters). But, it'd be better to ignore characters
unfamiliar to you and maybe never used.
katakana_before_hiragana
upper_before_lower
-- see 6.6 Case Comparisons; 7.3.1 Tertiary Weight Table, UTR #10.
By default, lowercase is before uppercase and hiragana is before
katakana.
If the tag is made true, this is reversed.
NOTE: These tags simplemindedly assume any lowercase/uppercase or
hiragana/katakana distinctions should occur in level 3, and their
weights at level 3 should be same as those mentioned in 7.3.1, UTR #10.
If you define your collation elements which violates this, these tags
doesn't work validly.
Methods for Collation
"@sorted = $Collator->sort(@not_sorted)"
Sorts a list of strings.
"$result = $Collator->cmp($a, $b)"
Returns 1 (when $a is greater than $b) or 0 (when $a is equal to $b) or
-1 (when $a is lesser than $b).
"$result = $Collator->eq($a, $b)"
"$result = $Collator->ne($a, $b)"
"$result = $Collator->lt($a, $b)"
"$result = $Collator->le($a, $b)"
"$result = $Collator->gt($a, $b)"
"$result = $Collator->ge($a, $b)"
They works like the same name operators as theirs.
eq : whether $a is equal to $b.
ne : whether $a is not equal to $b.
lt : whether $a is lesser than $b.
le : whether $a is lesser than $b or equal to $b.
gt : whether $a is greater than $b.
ge : whether $a is greater than $b or equal to $b.
"$sortKey = $Collator->getSortKey($string)"
-- see 4.3 Form a sort key for each string, UTR #10.
Returns a sort key.
You compare the sort keys using a binary comparison and get the result
of the comparison of the strings using UCA.
$Collator->getSortKey($a) cmp $Collator->getSortKey($b)
is equivalent to
$Collator->cmp($a, $b)
"$sortKeyForm = $Collator->viewSortKey($string)"
Returns a string formalized to display a sort key. Weights are
enclosed with '[' and ']' and level boundaries are denoted by '|'.
use Unicode::Collate;
my $c = Unicode::Collate->new();
print $c->viewSortKey("Perl"),"\n";
# output:
# [09B3 08B1 09CB 094F|0020 0020 0020 0020|0008 0002 0002 0002|FFFF FFFF FFFF FFFF]
# Level 1 Level 2 Level 3 Level 4
"$position = $Collator->index($string, $substring)"
"($position, $length) = $Collator->index($string, $substring)"
-- see 6.8 Searching, UTR #10.
If $substring matches a part of $string, returns the position of the
first occurrence of the matching part in scalar context; in list
context, returns a two-element list of the position and the length of
the matching part.
Notice that the length of the matching part may differ from the length
of $substring.
Note that the position and the length are counted on the string after
the process of preprocess, normalization, and rearrangement.
Therefore, in case the specified string is not binary equal to the
preprocessed/normalized/rearranged string, the position and the length
may differ form those on the specified string. But it is guaranteed
that, if matched, it returns a non-negative value as $position.
If $substring does not match any part of $string, returns "-1" in
scalar context and an empty list in list context.
e.g. you say
my $Collator = Unicode::Collate->new( normalization => undef, level => 1 );
my $str = "Ich mu\x{00DF} studieren.";
my $sub = "m\x{00FC}ss";
my $match;
if (my($pos,$len) = $Collator->index($str, $sub)) {
$match = substr($str, $pos, $len);
}
and get "mu\x{00DF}" in $match since ""mu"""" is primary equal to
""m""ss"".
Other Methods
UCA_Version
Returns the version number of Unicode Technical Standard 10 this module
consults.
Base_Unicode_Version
Returns the version number of the Unicode Standard this module is based
on.
EXPORT
None by default.
TODO
Unicode::Collate has not been ported to EBCDIC. The code mostly would work
just fine but a decision needs to be made: how the module should work in
EBCDIC? Should the low 256 characters be understood as Unicode or as
EBCDIC code points? Should one be chosen or should there be a way to do
either? Or should such translation be left outside the module for the user
to do, for example by using Encode::from_to()? (or
utf8::unicode_to_native()/utf8::native_to_unicode()?)
CAVEAT
Use of the "normalization" parameter requires the Unicode::Normalize
module.
If you need not it (say, in the case when you need not handle any combining
characters), assign "normalization => undef" explicitly.
-- see 6.5 Avoiding Normalization, UTR #10.
BUGS
"index()" is an experimental method and its return value may be unreliable.
The correct implementation for "index()" must be based on Locale-Sensitive
Support: Level 3 in UTR #18, Unicode Regular Expression Guidelines.
See also 4.2 Locale-Dependent Graphemes in UTR #18.
AUTHOR
SADAHIRO Tomoyuki, <SADAHIRO@cpan.org>
http://homepage1.nifty.com/nomenclator/perl/
Copyright(C) 2001-2002, SADAHIRO Tomoyuki. Japan. All rights reserved.
This library is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.
SEE ALSO
http://www.unicode.org/unicode/reports/tr10/
Unicode Collation Algorithm - UTR #10
http://www.unicode.org/unicode/reports/tr10/allkeys.txt
The Default Unicode Collation Element Table
http://www.unicode.org/unicode/reports/tr15/
Unicode Normalization Forms - UAX #15
http://www.unicode.org/unicode/reports/tr18
Unicode Regular Expression Guidelines - UTR #18
Unicode::Normalize
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