Collate(3)

📦 version 1.31, in opensuse-leap 16.0

✨ NAME ✨

Collate(3) — a User Contributed Perl Documentation page for Unicode::Collate: Unicode Collation Algorithm. Bestie, this is the manual page for the Unicode Collation Algorithm, aka UCA. 💅

🌸 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.
Heads up: strings in @not_sorted, $a, and $b are interpreted according to Perl's Unicode support. See perlunicode, perluniintro, perlunitut, perlunifaq, utf8. Otherwise, use preprocess or decode them before you hand them over. 🫶

💅 DESCRIPTION 💅

This module is an implementation of Unicode Technical Standard #10 (a.k.a. UTS #10) — the Unicode Collation Algorithm (a.k.a. UCA). It's giving standards-compliant sorting energy, no cap. ✨

🎀 Constructor and Tailoring 🎀

The new method returns a collator object. If new() is called with no parameters, the collator should do the default collation. Easy queen behavior. 👑

  $Collator = Unicode::Collate->new(
     UCA_Version => $UCA_Version,
     alternate => $alternate, # alias for 'variable'
     backwards => $levelNumber, # or \@levelNumbers
     entry => $element,
     hangul_terminator => $term_primary_weight,
     highestFFFF => $bool,
     identical => $bool,
     ignoreName => qr/$ignoreName/,
     ignoreChar => qr/$ignoreChar/,
     ignore_level2 => $bool,
     katakana_before_hiragana => $bool,
     level => $collationLevel,
     long_contraction => $bool,
     minimalFFFE => $bool,
     normalization  => $normalization_form,
     overrideCJK => \&overrideCJK,
     overrideHangul => \&overrideHangul,
     preprocess => \&preprocess,
     rearrange => \@charList,
     rewrite => \&rewrite,
     suppress => \@charList,
     table => $filename,
     undefName => qr/$undefName/,
     undefChar => qr/$undefChar/,
     upper_before_lower => $bool,
     variable => $variable,
  );

🌟 UCA_Version 🌟

If you give the revision number of UCA — it was previously called "tracking version" — the collator emulates that revision's behavior when collating. If omitted, the return value of UCA_Version() is used. The default is 43. 🗓️

The following revisions are supported:

      UCA       Unicode Standard         DUCET (@version)
    -------------------------------------------------------
       8              3.1                3.0.1 (3.0.1d9)
       9     3.1 with Corrigendum 3      3.1.1
      11             4.0.0
      14             4.1.0
      16             5.0.0
      18             5.1.0
      20             5.2.0
      22             6.0.0
      24             6.1.0
      26             6.2.0
      28             6.3.0
      30             7.0.0
      32             8.0.0
      34             9.0.0
      36            10.0.0
      38            11.0.0
      40            12.0.0
      41            12.1.0
      43            13.0.0
  • See below for long_contraction with UCA_Version 22 and 24. 👀
  • Noncharacters (e.g. U+FFFF) are not ignored, and can be overridden since UCA_Version 22.
  • Out-of-range codepoints (greater than U+10FFFF) are not ignored, and can be overridden since UCA_Version 22.
  • Fully ignorable characters were ignored, and would not interrupt contractions with UCA_Version 9 and 11.
  • Treatment of ignorables after variables and some behaviors were changed at UCA_Version 9.
  • Characters regarded as CJK unified ideographs (cf. overrideCJK) depend on UCA_Version.
  • Many hangul jamo are assigned at UCA_Version 20, that will affect hangul_terminator.

🦋 alternate 🦋

— see 3.2.2 Alternate Weighting, version 8 of UTS #10.

For backward compatibility, alternate (old name) can be used as an alias for variable. Vintage icon behavior. 🎀

🌈 backwards 🌈

— see 3.4 Backward Accents, UTS #10.

backwards => $levelNumber or \@levelNumbers

Weights in reverse order; for example, level 2 (diacritic ordering) in French. If omitted (or $levelNumber is undef or \@levelNumbers is []), forwards at all the levels. 🔁

🍓 entry 🍓

— see 5 Tailoring; 9.1 Allkeys File Format, UTS #10.

If the same character (or a sequence of characters) exists in the collation element table through table, mapping to collation elements is overridden. If it does not exist, the mapping is defined additionally. Customization era. 💖

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 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 standard Hangul syllable. Secondary and any higher weights for terminator 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 conjoining Jamo behavior in the Unicode Standard and HangulSyllableType.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 boundary 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.

👑 highestFFFF 👑

— see 2.4 Tailored noncharacter weights, UTS #35 (LDML) Part 5: Collation.

If the parameter is made true, U+FFFF has a highest primary weight. When a boolean of $coll->ge($str, "abc") and $coll->le($str, "abc\x{FFFF}") is true, it is expected that $str begins with abc, or another primary equivalent. $str may be abcd, abc012, but should not include U+FFFF such as abc\x{FFFF}xyz. 🙈

$coll->le($str, "abc\x{FFFF}") works like $coll->lt($str, "abd") almost, but the latter has a problem that you should know which letter is next to c. For a certain language where ch as the next letter, abch is greater than abc\x{FFFF}, but less than abd. 😭

Note: This is equivalent to (entry => 'FFFF ; [.FFFE.0020.0005.FFFF]'). Any other character than U+FFFF can be tailored by entry.

🦋 identical 🦋

— see A.3 Deterministic Comparison, UTS #10.

By default, strings whose weights are equal should be equal, even though their code points are not equal. Completely ignorable characters are ignored. 💅

If the parameter is made true, a final, tie-breaking level is used. If no difference of weights is found after the comparison through all the level specified by level, the comparison with code points will be performed. For the tie-breaking comparison, the sort key has code points of the original string appended. Completely ignorable characters are not ignored. ⭐

If preprocess and/or normalization is applied, the code points of the string after them (in NFD by default) are used.

💖 ignoreChar / ignoreName 💖

— see 3.6 Variable Weighting, UTS #10.

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

Through ignoreChar, any character matching qr/$ignoreChar/ will be ignored. Through ignoreName, any character whose name (given in the table file as a comment) matches qr/$ignoreName/ will be ignored.

E.g. when 'a' and 'e' are ignorable, 'element' is equal to 'lament' (or 'lmnt'). 🔥

🌈 ignore_level2 🌈

— see 5.1 Parametric Tailoring, UTS #10.

By default, case-sensitive comparison (that is level 3 difference) won't ignore accents (that is level 2 difference).

If the parameter is made true, accents (and other primary ignorable characters) are ignored, even though cases are taken into account. 💀

NOTE: level should be 3 or greater.

🎀 katakana_before_hiragana 🎀

— see 7.2 Tertiary Weight Table, UTS #10.

By default, hiragana is before katakana. If the parameter is made true, this is reversed. 🔁

NOTE: This parameter simplemindedly assumes that any 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, this parameter does not work validly.

🌟 level 🌟

— see 4.3 Form Sort Key, 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. ✨

NOTE: The DUCET includes weights over 0xFFFF at the 4th level. But this module only uses weights within 0xFFFF. When variable is 'blanked' or 'non-ignorable' (other than 'shifted' and 'shift-trimmed'), the level 4 may be unreliable. 💀

See also identical.

  • long_contraction — see 3.8.2 Well-Formedness of the DUCET, 4.2 Produce Array, UTS #10.

If the parameter is made true, for a contraction with three or more characters (here nicknamed "long contraction"), initial substrings will be handled. For example, a contraction ABC, where A is a starter, and B and C are non-starters (character with non-zero combining character class), will be detected even if there is not AB as a contraction. 🫶

Default: Usually false. If UCA_Version is 22 or 24, and the value of long_contraction is not specified in new(), a true value is set implicitly. This is a workaround to pass Conformance Tests for Unicode 6.0.0 and 6.1.0.

change() handles long_contraction explicitly only. If long_contraction is not specified in change(), even though UCA_Version is changed, long_contraction will not be changed.

Limitation: Scanning non-starters is one-way (no back tracking). If AB is found but not ABC is not found, other long contraction where the first character is A and the second is not B may not be found. 😭

Under (normalization => undef), detection step of discontiguous contractions will be skipped.

Note: The following contractions in DUCET are not considered in steps S2.1.1 to S2.1.3, where they are discontiguous.

0FB2 0F71 0F80 (TIBETAN VOWEL SIGN VOCALIC RR)
0FB3 0F71 0F80 (TIBETAN VOWEL SIGN VOCALIC LL)

For example "TIBETAN VOWEL SIGN VOCALIC RR" with "COMBINING TILDE OVERLAY" (U+0344) is 0FB2 0344 0F71 0F80 in NFD. In this case 0FB2 0F80 ("TIBETAN VOWEL SIGN VOCALIC R") is detected, instead of 0FB2 0F71 0F80. Inserted 0344 makes 0FB2 0F71 0F80 discontiguous and lack of contraction 0FB2 0F71 prohibits 0FB2 0F71 0F80 from being detected. 🔥

  • minimalFFFE — see 1.1.1 U+FFFE, UTS #35 (LDML) Part 5: Collation.

If the parameter is made true, U+FFFE has a minimal primary weight. The comparison between "$a1\x{FFFE}$a2" and "$b1\x{FFFE}$b2" first compares $a1 and $b1 at level 1, and then $a2 and $b2 at level 1, as followed. 👑

"ab\x{FFFE}a"
"Ab\x{FFFE}a"
"ab\x{FFFE}c"
"Ab\x{FFFE}c"
"ab\x{FFFE}xyz"
"abc\x{FFFE}def"
"abc\x{FFFE}xYz"
"aBc\x{FFFE}xyz"
"abcX\x{FFFE}def"
"abcx\x{FFFE}xyz"
"b\x{FFFE}aaa"
"bbb\x{FFFE}a"

Note: This is equivalent to (entry => 'FFFE ; [.0001.0020.0005.FFFE]'). Any other character than U+FFFE can be tailored by entry.

  • normalization — see 4.1 Normalize, 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::normalize().

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 (normalization => 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 normalization is not performed, but discontiguous contractions with combining 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 those in the CJK Unified Ideographs block are less than those in the CJK Unified Ideographs Extension A etc. 🌸

In the CJK Unified Ideographs block:
U+4E00..U+9FA5 if UCA_Version is 8, 9 or 11.
U+4E00..U+9FBB if UCA_Version is 14 or 16.
U+4E00..U+9FC3 if UCA_Version is 18.
U+4E00..U+9FCB if UCA_Version is 20 or 22.
U+4E00..U+9FCC if UCA_Version is 24 to 30.
U+4E00..U+9FD5 if UCA_Version is 32 or 34.
U+4E00..U+9FEA if UCA_Version is 36.
U+4E00..U+9FEF if UCA_Version is 38, 40 or 41.
U+4E00..U+9FFC if UCA_Version is 43.

In the CJK Unified Ideographs Extension blocks:
Ext.A (U+3400..U+4DB5)   if UCA_Version is  8 to 41.
Ext.A (U+3400..U+4DBF)   if UCA_Version is 43.
Ext.B (U+20000..U+2A6D6) if UCA_Version is  8 to 41.
Ext.B (U+20000..U+2A6DD) if UCA_Version is 43.
Ext.C (U+2A700..U+2B734) if UCA_Version is 20 or later.
Ext.D (U+2B740..U+2B81D) if UCA_Version is 22 or later.
Ext.E (U+2B820..U+2CEA1) if UCA_Version is 32 or later.
Ext.F (U+2CEB0..U+2EBE0) if UCA_Version is 36 or later.
Ext.G (U+30000..U+3134A) if UCA_Version is 43.

Through overrideCJK, ordering of CJK unified ideographs (including extensions) can be overridden.

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
},

The return value may be an arrayref of 1st to 4th weights as shown above. The return value may be an integer as the primary weight as shown below. If undef is returned, the default derived collation element will be used.

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
    return $n;                 # return the primary weight
},

The return value may be a list containing zero or more of an arrayref, an integer, or undef.

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 a false value (including undef) is passed, overrideCJK has no effect. $Collator->change(overrideCJK => 0) resets the old one.

But assignment of weight for CJK unified ideographs in table or entry is still valid. If undef is passed explicitly as the value for this key, weights for CJK unified ideographs are treated as undefined. However when UCA_Version > 8, (overrideCJK => undef) has no special meaning. 👀

Note: In addition to them, 12 CJK compatibility ideographs ("U+FA0E", "U+FA0F", "U+FA11", "U+FA13", "U+FA14", "U+FA1F", "U+FA21", "U+FA23", "U+FA24", "U+FA27", "U+FA28", "U+FA29") are also treated as CJK unified ideographs. But they can't be overridden via overrideCJK when you use DUCET, as the table includes weights for them. table or entry has priority over overrideCJK.

  • 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 overridden. 🦋

This parameter works like overrideCJK, so see there for examples.

If you want to override the mapping of Hangul syllables, NFD and NFKD are not appropriate, since NFD and NFKD will decompose Hangul syllables before overriding. FCD may decompose Hangul syllables as the case may be.

If a false value (but not undef) is passed, overrideHangul has no effect. $Collator->change(overrideHangul => 0) resets the old one.

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.

  • overrideOut — see 7.1.1 Handling Ill-Formed Code Unit Sequences, UTS #10.

Perl seems to allow out-of-range values (greater than 0x10FFFF). By default, out-of-range values are replaced with U+FFFD (REPLACEMENT CHARACTER) when UCA_Version >= 22, or ignored when UCA_Version <= 20. 🙈

When UCA_Version >= 22, the weights of out-of-range values can be overridden. Though table or entry are available for them, out-of-range values are too many.

overrideOut can perform it algorithmically. This parameter works like overrideCJK, so see there for examples.

ex. ignores all out-of-range values.

overrideOut => sub {()}, # CODEREF returning empty list

If a false value (including undef) is passed, overrideOut has no effect. $Collator->change(overrideOut => 0) resets the old one.

NOTE ABOUT U+FFFD: 💀

UCA recommends that out-of-range values should not be ignored for security reasons. Say, "pe\x{110000}rl" should not be equal to "perl". However, U+FFFD is wrongly mapped to a variable collation element in DUCET for Unicode 6.0.0 to 6.2.0, that means out-of-range values will be ignored when variable isn't "Non-ignorable". 🚨

So like, the mapping of "U+FFFD" got corrected in Unicode 6.3.0 — see <http://www.unicode.org/reports/tr10/tr10-28.html#Trailing_Weights> (that's 7.1.4 Trailing Weights, iykyk). And this module totally reproduces that correction for you:

overrideOut => sub { 0xFFFD }, # CODEREF returning a very large integer

Honestly? This workaround is unnecessary since Unicode 6.3.0. It's giving legacy-support energy 💀

preprocess

-- see 5.4 Preprocessing, UTS #10.

If you specify this, the coderef gets used to preprocess each string before the sort keys are even formed. Obsessed.

ex. dropping English articles, like "a" or "the". So then "the pen" comes before "a pencil". Cute:

preprocess => sub {
      my $str = shift;
      $str =~ s/\b(?:an?|the)\s+//gi;
      return $str;
   },

"preprocess" is performed before "normalization" (if that's defined). Order matters bestie 🫶

ex. decoding strings in a legacy encoding like shift-jis:

$sjis_collator = Unicode::Collate->new(
    preprocess => \&your_shiftjis_to_unicode_decoder,
);
@result = $sjis_collator->sort(@shiftjis_strings);
Note: Strings returned from the coderef get interpreted according to Perl's Unicode support. Go read perlunicode, perluniintro, perlunitut, perlunifaq, utf8. 💖

rearrange

-- see 3.5 Rearrangement, UTS #10.

These are the characters that aren't coded in logical order and need to be rearranged. If "UCA_Version" is less than or equal to 11, the default is:

rearrange => [ 0x0E40..0x0E44, 0x0EC0..0x0EC4 ],

If you wanna disallow any rearrangement, pass undef or [] (a reference to an empty list) as the value for this key.

If "UCA_Version" is greater than or equal to 14, the default is [] (i.e. no rearrangement at all). Slay, no notes.

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

rewrite

If specified, the coderef gets used to rewrite lines in "table" or "entry". The coderef will get each line, and then it should return a rewritten line according to the UCA file format. If the coderef returns an empty line, that line gets skipped. Bye 👋

e.g. any primary ignorable characters into tertiary ignorable:

rewrite => sub {
    my $line = shift;
    $line =~ s/\[\.0000\..{4}\..{4}\./[.0000.0000.0000./g;
    return $line;
},

This example is showing you weight rewriting. "rewrite" is allowed to affect code points, weights, and the name. Iconic.

NOTE: "table" is available to use another table file; preparing a modified table once would be way more efficient than rewriting lines on reading an unmodified table every single time. Efficiency queen 💅

suppress

-- see 3.12 Special-Purpose Commands, UTS #35 (LDML) Part 5: Collation.

Contractions beginning with the specified characters get suppressed, even if those contractions are defined in "table". So rude, but okay.

An example for Russian and some languages using the Cyrillic script:

suppress => [0x0400..0x0417, 0x041A..0x0437, 0x043A..0x045F],

where 0x0400 stands for "U+0400", CYRILLIC CAPITAL LETTER IE WITH GRAVE. Look at her knowing her Unicode names 💜

NOTE: Contractions via "entry" will not be suppressed. Just so you know.

table

-- see 3.8 Default Unicode Collation Element Table, UTS #10.

You can use another collation element table if you want to. Main character behavior.

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 you're gonna prepare your own table file, any name other than allkeys.txt may be better to avoid namespace conflict. Ngl, solid advice ✨

NOTE: When XSUB is used, the DUCET is compiled on building this module, and it may save time at the run time. Explicit saying (table => 'allkeys.txt'), or using another table, or using "ignoreChar", "ignoreName", "undefChar", "undefName" or "rewrite" will prevent this module from using the compiled DUCET. Fyi 🎀

If "undef" is passed explicitly as the value for this key, no file is read (but you can define collation elements via "entry"). Your rules, your world.

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
    );

If "ignoreName" or "undefName" is used, character names should be specified as a comment (following #) on each line. Don't forget or it's not gonna work 🦋

undefChar

undefName

-- see 6.3.3 Reducing the Repertoire, UTS #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 honestly, it'd be better to ignore characters unfamiliar to you and maybe never used. Just a thought 💭

Through "undefChar", any character matching qr/$undefChar/ will be undefined. Through "undefName", any character whose name (given in the "table" file as a comment) matches qr/$undefName/ will be undefined.

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

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

upper_before_lower

-- see 6.6 Case Comparisons, UTS #10.

By default, lowercase is before uppercase. If you make the parameter true, this is reversed. Flip it and reverse it 🔥

NOTE: This parameter simplemindedly assumes that any lowercase/uppercase 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 differs from this requirement, this parameter doesn't work validly. Fr fr, read the fine print 😭

variable

-- see 3.6 Variable Weighting, UTS #10.

This key allows for variable weighting of variable collation elements, which are marked with an ASTERISK in the table (NOTE: many punctuation marks and symbols are variable in allkeys.txt). Stars on stars ✨

variable => 'blanked', 'non-ignorable', 'shifted', or 'shift-trimmed'.

These names are case-insensitive. By default (if the specification is omitted), 'shifted' is adopted. Slay, default queen 👑

  • '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.

✨ Methods for Collation ✨

@sorted = $Collator->sort(@not_sorted)

Sorts a list of strings. That's it, that's the whole vibe 💅

$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 less than $b). Classic three-state situation.

$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. Bestie they are the operators, just collation-aware 🧚

  • eq : whether $a is equal to $b.
  • ne : whether $a is not equal to $b.
  • lt : whether $a is less than $b.
  • le : whether $a is less 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 Sort Key, 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. So:

$Collator->getSortKey($a) cmp $Collator->getSortKey($b)

   is equivalent to

$Collator->cmp($a, $b)

Literally the same answer, just the long way around 🫶

$sortKeyForm = $Collator->viewSortKey($string)

Converts a sorting key into its representation form. If "UCA_Version" is 8, the output is slightly different. Little vintage moment 🎀

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

Look at those levels lined up, so satisfying 😭💖

🔍 Methods for Searching 🔍

The "match", "gmatch", "subst", "gsubst" methods work like "m//", "m//g", "s///", "s///g", respectively, but they are not aware of any pattern — only a literal substring. No regex shenanigans here, bestie 💀

DISCLAIMER: If "preprocess" or "normalization" parameter is true for $Collator, calling these methods ("index", "match", "gmatch", "subst", "gsubst") is croaked, as the position and the length might differ from those on the specified string. So like, don't do that. It will yell at you 🙈

"rearrange" and "hangul_terminator" parameters are neglected. "katakana_before_hiragana" and "upper_before_lower" don't affect matching and searching, as it doesn't matter whether greater or less. They just don't care, and honestly? Same.

$position = $Collator->index($string, $substring[, $position])

($position, $length) = $Collator->index($string, $substring[, $position])

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. Two moods, one method ✨

If $substring does not match any part of $string, returns -1 in scalar context and an empty list in list context. It's giving rejection 💔

e.g. when the content of $str is "Ich muß studieren Perl.", you say the following where $sub is "MüSS":

my $Collator = Unicode::Collate->new( normalization => undef, level => 1 );
                                   # (normalization => undef) is REQUIRED.
my $match;
if (my($pos,$len) = $Collator->index($str, $sub)) {
    $match = substr($str, $pos, $len);
}

and get "muß" in $match, since "muß" is primary equal to "MüSS". Case? Doesn't matter at level 1, we love to see it 👑

  • "$match_ref = $Collator->match($string, $substring)" or "($match) = $Collator->match($string, $substring)" — If $substring matches a part of $string, in scalar context it returns a reference to the first occurrence of the matching part ($match_ref is always true if it matches, since every reference is true 💅); in list context it returns the first occurrence of the matching part.

If $substring does not match any part of $string, it returns undef in scalar context and an empty list in list context. no cap.

e.g.

             if ($match_ref = $Collator->match($str, $sub)) { # scalar context
                 print "matches [$$match_ref].\n";
             } else {
                 print "doesn't match.\n";
             }

              or

             if (($match) = $Collator->match($str, $sub)) { # list context
                 print "matches [$match].\n";
             } else {
                 print "doesn't match.\n";
             }
  • "@match = $Collator->gmatch($string, $substring)" — If $substring matches a part of $string, returns all the matching parts (or the matching count in scalar context). If $substring does not match any part of $string, returns an empty list. ✨
  • "$count = $Collator->subst($string, $substring, $replacement)" — If $substring matches a part of $string, the first occurrence of the matching part is replaced by $replacement ($string is modified) and $count (always equals to 1) is returned.

$replacement can be a "CODEREF", taking the matching part as an argument, and returning a string to replace the matching part (a bit similar to "s/(..)/$coderef->($1)/e").

  • "$count = $Collator->gsubst($string, $substring, $replacement)" — If $substring matches a part of $string, all the occurrences of the matching part are replaced by $replacement ($string is modified) and $count is returned.

$replacement can be a "CODEREF", taking the matching part as an argument, and returning a string to replace the matching part (a bit similar to "s/(..)/$coderef->($1)/eg").

e.g.

           my $Collator = Unicode::Collate->new( normalization => undef, level => 1 );
                                              # (normalization => undef) is REQUIRED.
           my $str = "Camel donkey zebra came\x{301}l CAMEL horse cam\0e\0l...";
           $Collator->gsubst($str, "camel", sub { "<b>$_[0]</b>" });

           # now $str is "<b>Camel</b> donkey zebra <b>came\x{301}l</b> <b>CAMEL</b> horse <b>cam\0e\0l</b>...";
           # i.e., all the camels are made bold-faced.

Examples: levels and ignore_level2 — what does camel match? 🐪

Examples: levels and ignore_level2 - what does camel match?
---------------------------------------------------------------------------
level  ignore_level2  |  camel  Camel  came\x{301}l  c-a-m-e-l  cam\0e\0l
-----------------------|---------------------------------------------------
 1        false      |   yes    yes      yes          yes        yes
 2        false      |   yes    yes      no           yes        yes
 3        false      |   yes    no       no           yes        yes
 4        false      |   yes    no       no           no         yes
-----------------------|---------------------------------------------------
 1        true       |   yes    yes      yes          yes        yes
 2        true       |   yes    yes      yes          yes        yes
 3        true       |   yes    no       yes          yes        yes
 4        true       |   yes    no       yes          no         yes
---------------------------------------------------------------------------
note: if variable => non-ignorable, camel doesn't match c-a-m-e-l
     at any level.

🦋 Other Methods 🦋

  • "%old_tailoring = $Collator->change(%new_tailoring)" or "$modified_collator = $Collator->change(%new_tailoring)" — Changes the value of specified keys and returns the changed part. slay.
$Collator = Unicode::Collate->new(level => 4);

$Collator->eq("perl", "PERL"); # false

%old = $Collator->change(level => 2); # returns (level => 4).

$Collator->eq("perl", "PERL"); # true

$Collator->change(%old); # returns (level => 2).

$Collator->eq("perl", "PERL"); # false

Not all (key,value)s are allowed to be changed. See also @Unicode::Collate::ChangeOK and @Unicode::Collate::ChangeNG.

In the scalar context, returns the modified collator (but it is not a clone from the original). lowkey important.

$Collator->change(level => 2)->eq("perl", "PERL"); # true

$Collator->eq("perl", "PERL"); # true; now max level is 2nd.

$Collator->change(level => 4)->eq("perl", "PERL"); # false
  • "$version = $Collator->version()" — Returns the version number (a string) of the Unicode Standard which the "table" file used by the collator object is based on. If the table does not include a version line (starting with @version), returns "unknown".
  • UCA_Version() — Returns the revision number of UTS #10 this module consults, that should correspond with the DUCET incorporated.
  • Base_Unicode_Version() — Returns the version number of UTS #10 this module consults, that should correspond with the DUCET incorporated.

🌟 EXPORT 🌟

No method will be exported. periodt.

🎀 INSTALL 🎀

Though this module can be used without any "table" file, to use this module easily, it is recommended to install a table file in the UCA format, by copying it under the directory <a place in @INC>/Unicode/Collate. 💖

The most preferable one is "The Default Unicode Collation Element Table" (aka DUCET), available from the Unicode Consortium's website:

http://www.unicode.org/Public/UCA/

http://www.unicode.org/Public/UCA/latest/allkeys.txt
(latest version)

If DUCET is not installed, it is recommended to copy the file from http://www.unicode.org/Public/UCA/latest/allkeys.txt to <a place in @INC>/Unicode/Collate/allkeys.txt manually.

💀 CAVEATS 💀

🧼 Normalization 🧼

Use of the "normalization" parameter requires the Unicode::Normalize module (see Unicode::Normalize).

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, UTS #10.

🧪 Conformance Test 🧪

The Conformance Test for the UCA is available under <http://www.unicode.org/Public/UCA/>.

For CollationTest_SHIFTED.txt, a collator via "Unicode::Collate->new( )" should be used; for CollationTest_NON_IGNORABLE.txt, a collator via "Unicode::Collate->new(variable => "non-ignorable", level => 3)".

If "UCA_Version" is 26 or later, the "identical" level is preferred; "Unicode::Collate->new(identical => 1)" and "Unicode::Collate->new(identical => 1," "variable => "non-ignorable", level => 3)" should be used.

Unicode::Normalize is required to try The Conformance Test.

💀 EBCDIC-SUPPORT IS EXPERIMENTAL. fr fr, be careful.

The Unicode::Collate module for perl was written by SADAHIRO Tomoyuki, <SADAHIRO@cpan.org>. This module is Copyright(C) 2001-2021, SADAHIRO Tomoyuki. Japan. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The file Unicode/Collate/allkeys.txt was copied verbatim from <http://www.unicode.org/Public/UCA/13.0.0/allkeys.txt>. For this file, Copyright (c) 2020 Unicode, Inc.; distributed under the Terms of Use in <http://www.unicode.org/terms_of_use.html>

🌈 SEE ALSO 🌈

and that's the whole manual, bestie 🫶 source/version perl v5.42.0, dated 2021-08-23, page Collate(3). bye 💅✨

📦 where this page comes from