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Unicode::Collate

Unicode::Collate(3)    Perl Programmers Reference Guide    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.

         # If %tailoring is false (i.e. empty),
         # $Collator should do the default collation.

DESCRIPTION
       This module is an implementation of Unicode Technical Standard #10 (UTS
       #10) "Unicode Collation Algorithm."

       Constructor and Tailoring

       The "new" method returns a collator object.

          $Collator = Unicode::Collate->new(
             UCA_Version => $UCA_Version,
             alternate => $alternate, # deprecated: use of 'variable' is recommended.
             backwards => $levelNumber, # or \@levelNumbers
             entry => $element,
             hangul_terminator => $term_primary_weight,
             ignoreName => qr/$ignoreName/,
             ignoreChar => qr/$ignoreChar/,
             katakana_before_hiragana => $bool,
             level => $collationLevel,
             normalization  => $normalization_form,
             overrideCJK => \&overrideCJK,
             overrideHangul => \&overrideHangul,
             preprocess => \&preprocess,
             rearrange => \@charList,
             table => $filename,
             undefName => qr/$undefName/,
             undefChar => qr/$undefChar/,
             upper_before_lower => $bool,
             variable => $variable,
          );

       UCA_Version
           If the tracking version number of the older UCA is given, the older
           behavior of that tracking version is emulated on collating.  If
           omitted, the return value of "UCA_Version()" is used.

           The supported tracking version: 8, 9, or 11.

           This parameter may be removed in the future version, as switching
           the algorithm would affect the performance.

       backwards
           -- see 3.1.2 French Accents, UTS #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, UTS #10.

           If the same character (or a sequence of characters) exists in the
           collation element table through "table", mapping to collation ele-
           ments is overrided.  If it does not exist, the mapping is defined
           additionally.

               entry => <<'ENTRY', # for DUCET v4.0.0 (allkeys-4.0.0.txt)
           0063 0068 ; [.0E6A.0020.0002.0063] # ch
           0043 0068 ; [.0E6A.0020.0007.0043] # Ch
           0043 0048 ; [.0E6A.0020.0008.0043] # CH
           006C 006C ; [.0F4C.0020.0002.006C] # ll
           004C 006C ; [.0F4C.0020.0007.004C] # Ll
           004C 004C ; [.0F4C.0020.0008.004C] # LL
           00F1      ; [.0F7B.0020.0002.00F1] # n-tilde
           006E 0303 ; [.0F7B.0020.0002.00F1] # n-tilde
           00D1      ; [.0F7B.0020.0008.00D1] # N-tilde
           004E 0303 ; [.0F7B.0020.0008.00D1] # N-tilde
           ENTRY

               entry => <<'ENTRY', # for DUCET v4.0.0 (allkeys-4.0.0.txt)
           00E6 ; [.0E33.0020.0002.00E6][.0E8B.0020.0002.00E6] # ae ligature as <a><e>
           00C6 ; [.0E33.0020.0008.00C6][.0E8B.0020.0008.00C6] # AE ligature as <A><E>
           ENTRY

           NOTE: The code point in the UCA file format (before ';') must be a
           Unicode code point (defined as hexadecimal), but not a native code
           point.  So 0063 must always denote "U+0063", but not a character of
           "\x63".

           Weighting may vary depending on collation element table.  So ensure
           the weights defined in "entry" will be consistent with those in the
           collation element table loaded via "table".

           In DUCET v4.0.0, primary weight of "C" is 0E60 and that of "D" is
           "0E6D". So setting primary weight of "CH" to "0E6A" (as a value
           between 0E60 and "0E6D") makes ordering as "C < CH < D".  Exactly
           speaking DUCET already has some characters between "C" and "D":
           "small capital C" ("U+1D04") with primary weight 0E64,
           "c-hook/C-hook" ("U+0188/U+0187") with 0E65, and "c-curl"
           ("U+0255") with 0E69.  Then primary weight "0E6A" for "CH" makes
           "CH" ordered between "c-curl" and "D".

       hangul_terminator
           -- see Condition B.2. in 7.1.4 Trailing Weights, UTS #10.

           If a true value is given (non-zero but should be positive), it will
           be added as a terminator primary weight to the end of every stan-
           dard Hangul syllable. Secondary and any higher weights for termina-
           tor are set to zero.  If the value is false or "hangul_terminator"
           key does not exist, insertion of terminator weights will not be
           performed.

           Boundaries of Hangul syllables are determined according to conjoin-
           ing Jamo behavior in the Unicode Standard and HangulSyllable-
           Type.txt.

           Implementation Note: (1) For expansion mapping (Unicode character
           mapped to a sequence of collation elements), a terminator will not
           be added between collation elements, even if Hangul syllable bound-
           ary exists there.  Addition of terminator is restricted to the next
           position to the last collation element.

           (2) Non-conjoining Hangul letters (Compatibility Jamo, halfwidth
           Jamo, and enclosed letters) are not automatically terminated with a
           terminator primary weight.  These characters may need terminator
           included in a collation element table beforehand.

       ignoreName
       ignoreChar
           -- see Completely Ignorable, 3.2.2 Variable Weighting, UTS #10.

           Makes the entry in the table completely ignorable; i.e. as if the
           weights were zero at all level.

           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, UTS #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 variable is 'shifted')

             ex.level => 2,

           If omitted, the maximum is the 4th.

       normalization
           -- see 4.1 Normalize each input string, UTS #10.

           If specified, strings are normalized before preparation of sort
           keys (the normalization is executed after preprocess).

           A form name "Unicode::Normalize::normalize()" accepts will be
           applied as $normalization_form.  Acceptable names include 'NFD',
           'NFC', 'NFKD', and 'NFKC'.  See "Unicode::Normalize::normalize()"
           for detail.  If omitted, 'NFD' is used.

           "normalization" is performed after "preprocess" (if defined).

           Furthermore, special values, "undef" and "prenormalized", can be
           used, though they are not concerned with "Unicode::Normalize::nor-
           malize()".

           If "undef" (not a string "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). Under "(nor-
           malization => undef)", only contiguous contractions are resolved;
           e.g. even if "A-ring" (and "A-ring-cedilla") is ordered after "Z",
           "A-cedilla-ring" would be primary equal to "A".  In this point,
           "(normalization => undef, preprocess => sub { NFD(shift) })" is not
           equivalent to "(normalization => 'NFD')".

           In the case of "(normalization => "prenormalized")", any normaliza-
           tion is not performed, but non-contiguous contractions with combin-
           ing characters are performed.  Therefore "(normalization =>
           'prenormalized', preprocess => sub { NFD(shift) })" is equivalent
           to "(normalization => 'NFD')".  If source strings are finely
           prenormalized, "(normalization => 'prenormalized')" may save time
           for normalization.

           Except "(normalization => undef)", Unicode::Normalize is required
           (see also CAVEAT).

       overrideCJK
           -- see 7.1 Derived Collation Elements, UTS #10.

           By default, CJK Unified Ideographs are ordered in Unicode codepoint
           order (but "CJK Unified Ideographs" ["U+4E00" to "U+9FA5"]  are
           lesser than "CJK Unified Ideographs Extension" ["U+3400" to
           "U+4DB5" and "U+20000" to "U+2A6D6"].

           Through "overrideCJK", ordering of CJK Unified Ideographs can 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 assign-
           ment of weight for CJK Unified Ideographs in table or "entry" is
           still valid.

       overrideHangul
           -- see 7.1 Derived Collation Elements, UTS #10.

           By default, Hangul Syllables are decomposed into Hangul Jamo, even
           if "(normalization => undef)".  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, NFD, NFKD,
           and FCD are not appropriate, since they will decompose Hangul Syl-
           lables 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, UTS #10.

           If specified, the coderef is used to preprocess before the forma-
           tion 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;
                      return $str;
                   },

           "preprocess" is performed before "normalization" (if defined).

       rearrange
           -- see 3.1.3 Rearrangement, UTS #10.

           Characters that are not coded in logical order and to be rear-
           ranged.  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.

           According to the version 9 of UCA, this parameter shall not be
           used; but it is not warned at present.

       table
           -- see 3.2 Default Unicode Collation Element Table, UTS #10.

           You can use another collation element table if desired.

           The table file should locate in the Unicode/Collate directory on
           @INC. Say, if the filename is Foo.txt the table file is searched as
           Unicode/Collate/Foo.txt in <@INC>.

           By default, allkeys.txt (as the filename of DUCET) 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, UTS #10.

           Undefines the collation element as if it were unassigned in the ta-
           ble.  This reduces the size of the table.  If an unassigned charac-
           ter 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 code-
           point order among the unassigned characters).  But, it'd be better
           to ignore characters unfamiliar to you and maybe never used.

           ex. Collation weights for beyond-BMP characters are not stored in
           object:

               undefChar => qr/[^\0-\x{fffd}]/,

       katakana_before_hiragana
       upper_before_lower
           -- see 6.6 Case Comparisons; 7.3.1 Tertiary Weight Table, UTS #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 must occur in level 3, and their
           weights at level 3 must be same as those mentioned in 7.3.1, UTS
           #10.  If you define your collation elements which violate this
           requirement, these tags don't work validly.

       variable
       alternate
           -- see 3.2.2 Variable Weighting, UTS #10.

           (the title in UCA version 8: Alternate Weighting)

           This key allows to variable weighting for variable collation ele-
           ments, which are marked with an ASTERISK in the table (NOTE: Many
           punction marks and symbols are variable in allkeys.txt).

              variable => '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 made ignorable at levels 1 through 3;
                               considered at the 4th level.

              'Non-Ignorable'  Variable elements are not reset to ignorable.

              'Shifted'        Variable elements are made 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.

           For backward compatibility, "alternate" can be used as an alias for
           "variable".

       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, UTS #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)"
              use Unicode::Collate;
              my $c = Unicode::Collate->new();
              print $c->viewSortKey("Perl"),"\n";

              # output:
              # [0B67 0A65 0B7F 0B03 | 0020 0020 0020 0020 | 0008 0002 0002 0002 | FFFF FFFF FFFF FFFF]
              #  Level 1               Level 2               Level 3               Level 4

               (If C<UCA_Version> is 8, the output is slightly different.)

       Methods for Searching

       DISCLAIMER: If "preprocess" or "normalization" tag is true for $Colla-
       tor, calling these methods ("index", "match", "gmatch", "subst",
       "gsubst") is croaked, as the position and the length might differ from
       those on the specified string.  (And "rearrange" and "hangul_termina-
       tor" tags are neglected.)

       The "match", "gmatch", "subst", "gsubst" methods work like "m//",
       "m//g", "s///", "s///g", respectively, but they are not aware of any
       pattern, but only a literal substring.

       "$position = $Collator->index($string, $substring[, $position])"
       "($position, $length) = $Collator->index($string, $substring[, $posi-
       tion])"
           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.

           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 );
                                                # (normalization => undef) is REQUIRED.
             my $str = "Ich mu



perl v5.8.6                       2001-09-21               Unicode::Collate(3)