Natural sorting

class String {
    # Sort groups of digits in number order. Sort by order of magnitude then lexically.
    -> naturally { self.lc.gsub(/(\d+)/, {|s1| "0" + s1.len.chr + s1 }) + "\x0" + self };

    # Collapse multiple ws characters to a single.
    -> collapse { self.gsub(/(\s)\1+/, {|s1| s1 }) };

    # Convert all ws characters to a space.
    -> normalize { self.gsub(/(\s)/, ' ') };

    # Ignore common leading articles for title sorts
    -> title { self.sub(/^(?:a|an|the)\b\s*/i, '') };

    # Decompose ISO-Latin1 glyphs to their base character.
    -> latin1_decompose {
        static tr = Hash.new(%w(
           Æ AE æ ae Þ TH þ th Ð TH ð th ß ss À A Á A Â A Ã A Ä A Å A à a á a
            â a ã a ä a å a Ç C ç c È E É E Ê E Ë E è e é e ê e ë e Ì I Í I Î
            I Ï I ì i í i î i ï i Ò O Ó O Ô O Õ O Ö O Ø O ò o ó o ô o õ o ö o
            ø o Ñ N ñ n Ù U Ú U Û U Ü U ù u ú u û u ü u Ý Y ÿ y ý y
        )...);

        var re = Regex.new('(' + tr.keys.join('|') + ')');
        self.gsub(re, {|s1| tr{s1} });
    }
}

Tests:

var tests = [
    [
        "Task 1a\nSort while ignoring leading spaces.",
        [
          'ignore leading spaces: 1', '   ignore leading spaces: 4',
          '  ignore leading spaces: 3', ' ignore leading spaces: 2'
        ],
        { .trim } # builtin method.
    ],
    [
        "Task 1b\nSort while ignoring multiple adjacent spaces.",
        [
          'ignore m.a.s   spaces: 3', 'ignore m.a.s spaces: 1',
          'ignore m.a.s    spaces: 4', 'ignore m.a.s  spaces: 2'
        ],
        { .collapse }
    ],
    [
        "Task 2\nSort with all white space normalized to regular spaces.",
        [
          "Normalized\tspaces: 4", "Normalized\xa0spaces: 1",
          "Normalized\x20spaces: 2", "Normalized\nspaces: 3"
        ],
        { .normalize }
    ],
    [
        "Task 3\nSort case independently.",
        [
          'caSE INDEPENDENT: 3', 'casE INDEPENDENT: 2',
          'cASE INDEPENDENT: 4', 'case INDEPENDENT: 1'
        ],
        { .lc } # builtin method
    ],
    [
        "Task 4\nSort groups of digits in natural number order.",
        %w(Foo100bar99baz0.txt foo100bar10baz0.txt foo1000bar99baz10.txt
           foo1000bar99baz9.txt 201st 32nd 3rd 144th 17th 2 95),
        { .naturally }
    ],
    [
        "Task 5 ( mixed with 1, 2, 3 & 4 )\n"
        + "Sort titles, normalize white space, collapse multiple spaces to\n"
        + "single, trim leading white space, ignore common leading articles\n"
        + 'and sort digit groups in natural order.',
        [
          'The Wind     in the Willows  8', '  The 39 Steps               3',
          'The    7th Seal              1', 'Wanda                        6',
          'A Fish Called Wanda          5', ' The Wind and the Lion       7',
          'Any Which Way But Loose      4', '12 Monkeys                   2'
        ],
        { .normalize.collapse.trim.title.naturally }
    ],
    [
        "Task 6, 7, 8\nMap letters in Latin1 that have accents or decompose to two\n"
        + 'characters to their base characters for sorting.',
        %w(apple Ball bald car Card above Æon æon aether
            niño nina e-mail Évian evoke außen autumn),
        { .latin1_decompose.naturally }
    ]
];

tests.each { |case|
    var code = case.pop;
    var array = case.pop;
    say case.pop+"\n";

    say "Standard Sort:\n";
    array.sort.each { .say };

    say "\nNatural Sort:\n";
    array.sort_by(code).each { .say };

    say "\n#{'*' * 40}\n";
}

Output:

Task 1a
Sort while ignoring leading spaces.

Standard Sort:

   ignore leading spaces: 4
  ignore leading spaces: 3
 ignore leading spaces: 2
ignore leading spaces: 1

Natural Sort:

ignore leading spaces: 1
 ignore leading spaces: 2
  ignore leading spaces: 3
   ignore leading spaces: 4

****************************************

Task 1b
Sort while ignoring multiple adjacent spaces.

Standard Sort:

ignore m.a.s    spaces: 4
ignore m.a.s   spaces: 3
ignore m.a.s  spaces: 2
ignore m.a.s spaces: 1

Natural Sort:

ignore m.a.s spaces: 1
ignore m.a.s  spaces: 2
ignore m.a.s   spaces: 3
ignore m.a.s    spaces: 4

****************************************

Task 2
Sort with all white space normalized to regular spaces.

Standard Sort:

Normalized      spaces: 4
Normalized
spaces: 3
Normalized spaces: 2
Normalized spaces: 1

Natural Sort:

Normalized spaces: 1
Normalized spaces: 2
Normalized
spaces: 3
Normalized      spaces: 4

****************************************

Task 3
Sort case independently.

Standard Sort:

cASE INDEPENDENT: 4
caSE INDEPENDENT: 3
casE INDEPENDENT: 2
case INDEPENDENT: 1

Natural Sort:

case INDEPENDENT: 1
casE INDEPENDENT: 2
caSE INDEPENDENT: 3
cASE INDEPENDENT: 4

****************************************

Task 4
Sort groups of digits in natural number order.

Standard Sort:

144th
17th
2
201st
32nd
3rd
95
Foo100bar99baz0.txt
foo1000bar99baz10.txt
foo1000bar99baz9.txt
foo100bar10baz0.txt

Natural Sort:

2
3rd
17th
32nd
95
144th
201st
foo100bar10baz0.txt
Foo100bar99baz0.txt
foo1000bar99baz9.txt
foo1000bar99baz10.txt

****************************************

Task 5 ( mixed with 1, 2, 3 & 4 )
Sort titles, normalize white space, collapse multiple spaces to
single, trim leading white space, ignore common leading articles
and sort digit groups in natural order.

Standard Sort:

  The 39 Steps               3
 The Wind and the Lion       7
12 Monkeys                   2
A Fish Called Wanda          5
Any Which Way But Loose      4
The    7th Seal              1
The Wind     in the Willows  8
Wanda                        6

Natural Sort:

The    7th Seal              1
12 Monkeys                   2
  The 39 Steps               3
Any Which Way But Loose      4
A Fish Called Wanda          5
Wanda                        6
 The Wind and the Lion       7
The Wind     in the Willows  8

****************************************

Task 6, 7, 8
Map letters in Latin1 that have accents or decompose to two
characters to their base characters for sorting.

Standard Sort:

Ball
Card
above
aether
apple
autumn
außen
bald
car
e-mail
evoke
nina
niño
Æon
Évian
æon

Natural Sort:

above
Æon
æon
aether
apple
außen
autumn
bald
Ball
car
Card
e-mail
Évian
evoke
nina
niño

****************************************