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Module std.uni

The std.uni module provides an implementation of fundamental Unicode algorithms and data structures. This doesn't include UTF encoding and decoding primitives, see std.utf.decode and std.utf.encode in std.utf for this functionality.

Category Functions
Decode byCodePoint byGrapheme decodeGrapheme graphemeStride
Comparison icmp sicmp
Classification isAlpha isAlphaNum isCodepointSet isControl isFormat isGraphical isIntegralPair isMark isNonCharacter isNumber isPrivateUse isPunctuation isSpace isSurrogate isSurrogateHi isSurrogateLo isSymbol isWhite
Normalization NFC NFD NFKD NormalizationForm normalize
Decompose decompose decomposeHangul UnicodeDecomposition
Compose compose composeJamo
Sets CodepointInterval CodepointSet InversionList unicode
Trie codepointSetTrie CodepointSetTrie codepointTrie CodepointTrie toTrie toDelegate
Casing asCapitalized asLowerCase asUpperCase isLower isUpper toLower toLowerInPlace toUpper toUpperInPlace
Utf8Matcher isUtfMatcher MatcherConcept utfMatcher
Separators lineSep nelSep paraSep
Building blocks allowedIn combiningClass Grapheme

All primitives listed operate on Unicode characters and sets of characters. For functions which operate on ASCII characters and ignore Unicode characters, see std.ascii. For definitions of Unicode character, code point and other terms used throughout this module see the terminology section below.

The focus of this module is the core needs of developing Unicode-aware applications. To that effect it provides the following optimized primitives:

It's recognized that an application may need further enhancements and extensions, such as less commonly known algorithms, or tailoring existing ones for region specific needs. To help users with building any extra functionality beyond the core primitives, the module provides:

  • CodepointSet, a type for easy manipulation of sets of characters. Besides the typical set algebra it provides an unusual feature: a D source code generator for detection of code points in this set. This is a boon for meta-programming parser frameworks, and is used internally to power classification in small sets like isWhite.
  • A way to construct optimal packed multi-stage tables also known as a special case of Trie. The functions codepointTrie, codepointSetTrie construct custom tries that map dchar to value. The end result is a fast and predictable Ο(1) lookup that powers functions like isAlpha and combiningClass, but for user-defined data sets.
  • A useful technique for Unicode-aware parsers that perform character classification of encoded code points is to avoid unnecassary decoding at all costs. utfMatcher provides an improvement over the usual workflow of decode-classify-process, combining the decoding and classification steps. By extracting necessary bits directly from encoded code units matchers achieve significant performance improvements. See MatcherConcept for the common interface of UTF matchers.
  • Generally useful building blocks for customized normalization: combiningClass for querying combining class and allowedIn for testing the Quick_Check property of a given normalization form.
  • Access to a large selection of commonly used sets of code points. Supported sets include Script, Block and General Category. The exact contents of a set can be observed in the CLDR utility, on the property index page of the Unicode website. See unicode for easy and (optionally) compile-time checked set queries.

Synopsis

import std.uni;
void main()
{
    // initialize code point sets using script/block or property name
    // now 'set' contains code points from both scripts.
    auto set = unicode("Cyrillic") | unicode("Armenian");
    // same thing but simpler and checked at compile-time
    auto ascii = unicode.ASCII;
    auto currency = unicode.Currency_Symbol;

    // easy set ops
    auto a = set & ascii;
    assert(a.empty); // as it has no intersection with ascii
    a = set | ascii;
    auto b = currency - a; // subtract all ASCII, Cyrillic and Armenian

    // some properties of code point sets
    assert(b.length > 45); // 46 items in Unicode 6.1, even more in 6.2
    // testing presence of a code point in a set
    // is just fine, it is O(logN)
    assert(!b['$']);
    assert(!b['\u058F']); // Armenian dram sign
    assert(b['¥']);

    // building fast lookup tables, these guarantee O(1) complexity
    // 1-level Trie lookup table essentially a huge bit-set ~262Kb
    auto oneTrie = toTrie!1(b);
    // 2-level far more compact but typically slightly slower
    auto twoTrie = toTrie!2(b);
    // 3-level even smaller, and a bit slower yet
    auto threeTrie = toTrie!3(b);
    assert(oneTrie['£']);
    assert(twoTrie['£']);
    assert(threeTrie['£']);

    // build the trie with the most sensible trie level
    // and bind it as a functor
    auto cyrillicOrArmenian = toDelegate(set);
    auto balance = find!(cyrillicOrArmenian)("Hello ընկեր!");
    assert(balance == "ընկեր!");
    // compatible with bool delegate(dchar)
    bool delegate(dchar) bindIt = cyrillicOrArmenian;

    // Normalization
    string s = "Plain ascii (and not only), is always normalized!";
    assert(s is normalize(s));// is the same string

    string nonS = "A\u0308ffin"; // A ligature
    auto nS = normalize(nonS); // to NFC, the W3C endorsed standard
    assert(nS == "Äffin");
    assert(nS != nonS);
    string composed = "Äffin";

    assert(normalize!NFD(composed) == "A\u0308ffin");
    // to NFKD, compatibility decomposition useful for fuzzy matching/searching
    assert(normalize!NFKD("2¹⁰") == "210");
}

Terminology

The following is a list of important Unicode notions and definitions. Any conventions used specifically in this module alone are marked as such. The descriptions are based on the formal definition as found in chapter three of The Unicode Standard Core Specification.

Abstract character
A unit of information used for the organization, control, or representation of textual data. Note that:
  • When representing data, the nature of that data is generally symbolic as opposed to some other kind of data (for example, visual).
  • An abstract character has no concrete form and should not be confused with a glyph.
  • An abstract character does not necessarily correspond to what a user thinks of as a “character” and should not be confused with a Grapheme.
  • The abstract characters encoded (see Encoded character) are known as Unicode abstract characters.
  • Abstract characters not directly encoded by the Unicode Standard can often be represented by the use of combining character sequences.

Canonical decomposition
The decomposition of a character or character sequence that results from recursively applying the canonical mappings found in the Unicode Character Database and these described in Conjoining Jamo Behavior (section 12 of Unicode Conformance).

Canonical composition
The precise definition of the Canonical composition is the algorithm as specified in Unicode Conformance section 11. Informally it's the process that does the reverse of the canonical decomposition with the addition of certain rules that e.g. prevent legacy characters from appearing in the composed result.

Canonical equivalent
Two character sequences are said to be canonical equivalents if their full canonical decompositions are identical.

Character
Typically differs by context. For the purpose of this documentation the term character implies encoded character, that is, a code point having an assigned abstract character (a symbolic meaning).

Code point
Any value in the Unicode codespace; that is, the range of integers from 0 to 10FFFF (hex). Not all code points are assigned to encoded characters.

Code unit
The minimal bit combination that can represent a unit of encoded text for processing or interchange. Depending on the encoding this could be: 8-bit code units in the UTF-8 (char), 16-bit code units in the UTF-16 (wchar), and 32-bit code units in the UTF-32 (dchar). Note that in UTF-32, a code unit is a code point and is represented by the D dchar type.

Combining character
A character with the General Category of Combining Mark(M).
  • All characters with non-zero canonical combining class are combining characters, but the reverse is not the case: there are combining characters with a zero combining class.
  • These characters are not normally used in isolation unless they are being described. They include such characters as accents, diacritics, Hebrew points, Arabic vowel signs, and Indic matras.

Combining class
A numerical value used by the Unicode Canonical Ordering Algorithm to determine which sequences of combining marks are to be considered canonically equivalent and which are not.

Compatibility decomposition
The decomposition of a character or character sequence that results from recursively applying both the compatibility mappings and the canonical mappings found in the Unicode Character Database, and those described in Conjoining Jamo Behavior no characters can be further decomposed.

Compatibility equivalent
Two character sequences are said to be compatibility equivalents if their full compatibility decompositions are identical.

Encoded character
An association (or mapping) between an abstract character and a code point.

Glyph
The actual, concrete image of a glyph representation having been rasterized or otherwise imaged onto some display surface.

Grapheme base
A character with the property Grapheme_Base, or any standard Korean syllable block.

Grapheme cluster
Defined as the text between grapheme boundaries as specified by Unicode Standard Annex #29, Unicode text segmentation. Important general properties of a grapheme:
  • The grapheme cluster represents a horizontally segmentable unit of text, consisting of some grapheme base (which may consist of a Korean syllable) together with any number of nonspacing marks applied to it.
  • A grapheme cluster typically starts with a grapheme base and then extends across any subsequent sequence of nonspacing marks. A grapheme cluster is most directly relevant to text rendering and processes such as cursor placement and text selection in editing, but may also be relevant to comparison and searching.
  • For many processes, a grapheme cluster behaves as if it was a single character with the same properties as its grapheme base. Effectively, nonspacing marks apply graphically to the base, but do not change its properties.

This module defines a number of primitives that work with graphemes: Grapheme, decodeGrapheme and graphemeStride. All of them are using extended grapheme boundaries as defined in the aforementioned standard annex.

Nonspacing mark
A combining character with the General Category of Nonspacing Mark (Mn) or Enclosing Mark (Me).

Spacing mark
A combining character that is not a nonspacing mark.

Normalization

The concepts of canonical equivalent or compatibility equivalent characters in the Unicode Standard make it necessary to have a full, formal definition of equivalence for Unicode strings. String equivalence is determined by a process called normalization, whereby strings are converted into forms which are compared directly for identity. This is the primary goal of the normalization process, see the function normalize to convert into any of the four defined forms.

A very important attribute of the Unicode Normalization Forms is that they must remain stable between versions of the Unicode Standard. A Unicode string normalized to a particular Unicode Normalization Form in one version of the standard is guaranteed to remain in that Normalization Form for implementations of future versions of the standard.

The Unicode Standard specifies four normalization forms. Informally, two of these forms are defined by maximal decomposition of equivalent sequences, and two of these forms are defined by maximal composition of equivalent sequences.

The choice of the normalization form depends on the particular use case. NFC is the best form for general text, since it's more compatible with strings converted from legacy encodings. NFKC is the preferred form for identifiers, especially where there are security concerns. NFD and NFKD are the most useful for internal processing.

Construction of lookup tables

The Unicode standard describes a set of algorithms that depend on having the ability to quickly look up various properties of a code point. Given the the codespace of about 1 million code points, it is not a trivial task to provide a space-efficient solution for the multitude of properties.

Common approaches such as hash-tables or binary search over sorted code point intervals (as in InversionList) are insufficient. Hash-tables have enormous memory footprint and binary search over intervals is not fast enough for some heavy-duty algorithms.

The recommended solution (see Unicode Implementation Guidelines) is using multi-stage tables that are an implementation of the Trie data structure with integer keys and a fixed number of stages. For the remainder of the section this will be called a fixed trie. The following describes a particular implementation that is aimed for the speed of access at the expense of ideal size savings.

Taking a 2-level Trie as an example the principle of operation is as follows. Split the number of bits in a key (code point, 21 bits) into 2 components (e.g. 15 and 8). The first is the number of bits in the index of the trie and the other is number of bits in each page of the trie. The layout of the trie is then an array of size 2^^bits-of-index followed an array of memory chunks of size 2^^bits-of-page/bits-per-element.

The number of pages is variable (but not less then 1) unlike the number of entries in the index. The slots of the index all have to contain a number of a page that is present. The lookup is then just a couple of operations - slice the upper bits, lookup an index for these, take a page at this index and use the lower bits as an offset within this page. Assuming that pages are laid out consequently in one array at pages, the pseudo-code is:

auto elemsPerPage = (2 ^^ bits_per_page) / Value.sizeOfInBits;
pages[index[n >> bits_per_page]][n & (elemsPerPage - 1)];

Where if elemsPerPage is a power of 2 the whole process is a handful of simple instructions and 2 array reads. Subsequent levels of the trie are introduced by recursing on this notion - the index array is treated as values. The number of bits in index is then again split into 2 parts, with pages over 'current-index' and the new 'upper-index'.

For completeness a level 1 trie is simply an array. The current implementation takes advantage of bit-packing values when the range is known to be limited in advance (such as bool). See also BitPacked for enforcing it manually. The major size advantage however comes from the fact that multiple identical pages on every level are merged by construction.

The process of constructing a trie is more involved and is hidden from the user in a form of the convenience functions codepointTrie, codepointSetTrie and the even more convenient toTrie. In general a set or built-in AA with dchar type can be turned into a trie. The trie object in this module is read-only (immutable); it's effectively frozen after construction.

Unicode properties

This is a full list of Unicode properties accessible through unicode with specific helpers per category nested within. Consult the CLDR utility when in doubt about the contents of a particular set.

General category sets listed below are only accessible with the unicode shorthand accessor.

General category
Abb. Long form Abb. Long formAbb. Long form
L Letter Cn Unassigned Po Other_Punctuation
Ll Lowercase_Letter Co Private_Use Ps Open_Punctuation
Lm Modifier_Letter Cs Surrogate S Symbol
Lo Other_Letter N Number Sc Currency_Symbol
Lt Titlecase_Letter Nd Decimal_Number Sk Modifier_Symbol
Lu Uppercase_Letter Nl Letter_Number Sm Math_Symbol
M Mark No Other_Number So Other_Symbol
Mc Spacing_Mark P Punctuation Z Separator
Me Enclosing_Mark Pc Connector_Punctuation Zl Line_Separator
Mn Nonspacing_Mark Pd Dash_Punctuation Zp Paragraph_Separator
C Other Pe Close_Punctuation Zs Space_Separator
Cc Control Pf Final_Punctuation - Any
Cf Format Pi Initial_Punctuation - ASCII

Sets for other commonly useful properties that are accessible with unicode:

Common binary properties
Name Name Name
Alphabetic Ideographic Other_Uppercase
ASCII_Hex_Digit IDS_Binary_Operator Pattern_Syntax
Bidi_Control ID_Start Pattern_White_Space
Cased IDS_Trinary_Operator Quotation_Mark
Case_Ignorable Join_Control Radical
Dash Logical_Order_Exception Soft_Dotted
Default_Ignorable_Code_Point Lowercase STerm
Deprecated Math Terminal_Punctuation
Diacritic Noncharacter_Code_Point Unified_Ideograph
Extender Other_Alphabetic Uppercase
Grapheme_Base Other_Default_Ignorable_Code_Point Variation_Selector
Grapheme_Extend Other_Grapheme_Extend White_Space
Grapheme_Link Other_ID_Continue XID_Continue
Hex_Digit Other_ID_Start XID_Start
Hyphen Other_Lowercase
ID_Continue Other_Math

Below is the table with block names accepted by unicode.block. Note that the shorthand version unicode requires "In" to be prepended to the names of blocks so as to disambiguate scripts and blocks.

Blocks
Aegean Numbers Ethiopic Extended Mongolian
Alchemical Symbols Ethiopic Extended-A Musical Symbols
Alphabetic Presentation Forms Ethiopic Supplement Myanmar
Ancient Greek Musical Notation General Punctuation Myanmar Extended-A
Ancient Greek Numbers Geometric Shapes New Tai Lue
Ancient Symbols Georgian NKo
Arabic Georgian Supplement Number Forms
Arabic Extended-A Glagolitic Ogham
Arabic Mathematical Alphabetic Symbols Gothic Ol Chiki
Arabic Presentation Forms-A Greek and Coptic Old Italic
Arabic Presentation Forms-B Greek Extended Old Persian
Arabic Supplement Gujarati Old South Arabian
Armenian Gurmukhi Old Turkic
Arrows Halfwidth and Fullwidth Forms Optical Character Recognition
Avestan Hangul Compatibility Jamo Oriya
Balinese Hangul Jamo Osmanya
Bamum Hangul Jamo Extended-A Phags-pa
Bamum Supplement Hangul Jamo Extended-B Phaistos Disc
Basic Latin Hangul Syllables Phoenician
Batak Hanunoo Phonetic Extensions
Bengali Hebrew Phonetic Extensions Supplement
Block Elements High Private Use Surrogates Playing Cards
Bopomofo High Surrogates Private Use Area
Bopomofo Extended Hiragana Rejang
Box Drawing Ideographic Description Characters Rumi Numeral Symbols
Brahmi Imperial Aramaic Runic
Braille Patterns Inscriptional Pahlavi Samaritan
Buginese Inscriptional Parthian Saurashtra
Buhid IPA Extensions Sharada
Byzantine Musical Symbols Javanese Shavian
Carian Kaithi Sinhala
Chakma Kana Supplement Small Form Variants
Cham Kanbun Sora Sompeng
Cherokee Kangxi Radicals Spacing Modifier Letters
CJK Compatibility Kannada Specials
CJK Compatibility Forms Katakana Sundanese
CJK Compatibility Ideographs Katakana Phonetic Extensions Sundanese Supplement
CJK Compatibility Ideographs Supplement Kayah Li Superscripts and Subscripts
CJK Radicals Supplement Kharoshthi Supplemental Arrows-A
CJK Strokes Khmer Supplemental Arrows-B
CJK Symbols and Punctuation Khmer Symbols Supplemental Mathematical Operators
CJK Unified Ideographs Lao Supplemental Punctuation
CJK Unified Ideographs Extension A Latin-1 Supplement Supplementary Private Use Area-A
CJK Unified Ideographs Extension B Latin Extended-A Supplementary Private Use Area-B
CJK Unified Ideographs Extension C Latin Extended Additional Syloti Nagri
CJK Unified Ideographs Extension D Latin Extended-B Syriac
Combining Diacritical Marks Latin Extended-C Tagalog
Combining Diacritical Marks for Symbols Latin Extended-D Tagbanwa
Combining Diacritical Marks Supplement Lepcha Tags
Combining Half Marks Letterlike Symbols Tai Le
Common Indic Number Forms Limbu Tai Tham
Control Pictures Linear B Ideograms Tai Viet
Coptic Linear B Syllabary Tai Xuan Jing Symbols
Counting Rod Numerals Lisu Takri
Cuneiform Low Surrogates Tamil
Cuneiform Numbers and Punctuation Lycian Telugu
Currency Symbols Lydian Thaana
Cypriot Syllabary Mahjong Tiles Thai
Cyrillic Malayalam Tibetan
Cyrillic Extended-A Mandaic Tifinagh
Cyrillic Extended-B Mathematical Alphanumeric Symbols Transport And Map Symbols
Cyrillic Supplement Mathematical Operators Ugaritic
Deseret Meetei Mayek Unified Canadian Aboriginal Syllabics
Devanagari Meetei Mayek Extensions Unified Canadian Aboriginal Syllabics Extended
Devanagari Extended Meroitic Cursive Vai
Dingbats Meroitic Hieroglyphs Variation Selectors
Domino Tiles Miao Variation Selectors Supplement
Egyptian Hieroglyphs Miscellaneous Mathematical Symbols-A Vedic Extensions
Emoticons Miscellaneous Mathematical Symbols-B Vertical Forms
Enclosed Alphanumerics Miscellaneous Symbols Yijing Hexagram Symbols
Enclosed Alphanumeric Supplement Miscellaneous Symbols and Arrows Yi Radicals
Enclosed CJK Letters and Months Miscellaneous Symbols And Pictographs Yi Syllables
Enclosed Ideographic Supplement Miscellaneous Technical
Ethiopic Modifier Tone Letters

Below is the table with script names accepted by unicode.script and by the shorthand version unicode:

Scripts
Arabic Hanunoo Old_Italic
Armenian Hebrew Old_Persian
Avestan Hiragana Old_South_Arabian
Balinese Imperial_Aramaic Old_Turkic
Bamum Inherited Oriya
Batak Inscriptional_Pahlavi Osmanya
Bengali Inscriptional_Parthian Phags_Pa
Bopomofo Javanese Phoenician
Brahmi Kaithi Rejang
Braille Kannada Runic
Buginese Katakana Samaritan
Buhid Kayah_Li Saurashtra
Canadian_Aboriginal Kharoshthi Sharada
Carian Khmer Shavian
Chakma Lao Sinhala
Cham Latin Sora_Sompeng
Cherokee Lepcha Sundanese
Common Limbu Syloti_Nagri
Coptic Linear_B Syriac
Cuneiform Lisu Tagalog
Cypriot Lycian Tagbanwa
Cyrillic Lydian Tai_Le
Deseret Malayalam Tai_Tham
Devanagari Mandaic Tai_Viet
Egyptian_Hieroglyphs Meetei_Mayek Takri
Ethiopic Meroitic_Cursive Tamil
Georgian Meroitic_Hieroglyphs Telugu
Glagolitic Miao Thaana
Gothic Mongolian Thai
Greek Myanmar Tibetan
Gujarati New_Tai_Lue Tifinagh
Gurmukhi Nko Ugaritic
Han Ogham Vai
Hangul Ol_Chiki Yi

Below is the table of names accepted by unicode.hangulSyllableType.

Hangul syllable type
Abb. Long form
L Leading_Jamo
LV LV_Syllable
LVT LVT_Syllable
T Trailing_Jamo
V Vowel_Jamo

References

ASCII Table, Wikipedia, The Unicode Consortium, Unicode normalization forms, Unicode text segmentation Unicode Implementation Guidelines Unicode Conformance

Trademarks

Unicode(tm) is a trademark of Unicode, Inc.

Standards

Unicode v6.2

Functions

Name Description
allowedIn Tests if dchar ch is always allowed (Quick_Check=YES) in normalization form norm.
asCapitalized Capitalize input range or string, meaning convert the first character to upper case and subsequent characters to lower case.
asLowerCase Convert input range or string to upper or lower case.
asUpperCase Convert input range or string to upper or lower case.
byCodePoint

Lazily transform a range of Graphemes to a range of code points.

byGrapheme

Iterate a string by grapheme.

combiningClass

Returns the combining class of ch.

compose Try to canonically compose 2 characters. Returns the composed character if they do compose and dchar.init otherwise.
composeJamo Try to compose hangul syllable out of a leading consonant (lead), a vowel and optional trailing consonant jamos.
decodeGrapheme Reads one full grapheme cluster from an input range of dchar inp.
decompose Returns a full Canonical (by default) or Compatibility decomposition of character ch. If no decomposition is available returns a Grapheme with the ch itself.
decomposeHangul Decomposes a Hangul syllable. If ch is not a composed syllable then this function returns Grapheme containing only ch as is.
graphemeStride Computes the length of grapheme cluster starting at index. Both the resulting length and the index are measured in code units.
icmp Does case insensitive comparison of r1 and r2. Follows the rules of full case-folding mapping. This includes matching as equal german ß with "ss" and other 1:M code point mappings unlike sicmp. The cost of icmp being pedantically correct is slightly worse performance.
isAlpha Returns whether c is a Unicode alphabetic character (general Unicode category: Alphabetic).
isAlphaNum Returns whether c is a Unicode alphabetic character or number. (general Unicode category: Alphabetic, Nd, Nl, No).
isControl Returns whether c is a Unicode control character (general Unicode category: Cc).
isFormat Returns whether c is a Unicode formatting character (general Unicode category: Cf).
isGraphical Returns whether c is a Unicode graphical character (general Unicode category: L, M, N, P, S, Zs).
isLower Return whether c is a Unicode lowercase character.
isMark Returns whether c is a Unicode mark (general Unicode category: Mn, Me, Mc).
isNonCharacter Returns whether c is a Unicode non-character i.e. a code point with no assigned abstract character. (general Unicode category: Cn)
isNumber Returns whether c is a Unicode numerical character (general Unicode category: Nd, Nl, No).
isPrivateUse Returns whether c is a Unicode Private Use code point (general Unicode category: Co).
isPunctuation Returns whether c is a Unicode punctuation character (general Unicode category: Pd, Ps, Pe, Pc, Po, Pi, Pf).
isSpace Returns whether c is a Unicode space character (general Unicode category: Zs)
isSurrogate Returns whether c is a Unicode surrogate code point (general Unicode category: Cs).
isSurrogateHi Returns whether c is a Unicode high surrogate (lead surrogate).
isSurrogateLo Returns whether c is a Unicode low surrogate (trail surrogate).
isSymbol Returns whether c is a Unicode symbol character (general Unicode category: Sm, Sc, Sk, So).
isUpper Return whether c is a Unicode uppercase character.
isWhite Whether or not c is a Unicode whitespace character. (general Unicode category: Part of C0(tab, vertical tab, form feed, carriage return, and linefeed characters), Zs, Zl, Zp, and NEL(U+0085))
normalize Returns input string normalized to the chosen form. Form C is used by default.
sicmp

Does basic case-insensitive comparison of r1 and r2. This function uses simpler comparison rule thus achieving better performance than icmp. However keep in mind the warning below.

toDelegate

Builds a Trie with typically optimal speed-size trade-off and wraps it into a delegate of the following type: bool delegate(dchar ch).

toLower If c is a Unicode uppercase character, then its lowercase equivalent is returned. Otherwise c is returned.
toLower Returns a string which is identical to s except that all of its characters are converted to lowercase (by preforming Unicode lowercase mapping). If none of s characters were affected, then s itself is returned.
toLowerInPlace Converts s to lowercase (by performing Unicode lowercase mapping) in place. For a few characters string length may increase after the transformation, in such a case the function reallocates exactly once. If s does not have any uppercase characters, then s is unaltered.
toTrie Convenience function to construct optimal configurations for packed Trie from any set of code points.
toUpper If c is a Unicode lowercase character, then its uppercase equivalent is returned. Otherwise c is returned.
toUpper Returns a string which is identical to s except that all of its characters are converted to uppercase (by preforming Unicode uppercase mapping). If none of s characters were affected, then s itself is returned.
toUpperInPlace Converts s to uppercase (by performing Unicode uppercase mapping) in place. For a few characters string length may increase after the transformation, in such a case the function reallocates exactly once. If s does not have any lowercase characters, then s is unaltered.
utfMatcher Constructs a matcher object to classify code points from the set for encoding that has Char as code unit.

Structs

Name Description
CodepointInterval The recommended type of std.typecons.Tuple to represent [a, b) intervals of code points. As used in InversionList. Any interval type should pass isIntegralPair trait.
Grapheme

A structure designed to effectively pack characters of a grapheme cluster.

InversionList

InversionList is a set of code points represented as an array of open-right [a, b) intervals (see CodepointInterval above). The name comes from the way the representation reads left to right. For instance a set of all values [10, 50), [80, 90), plus a singular value 60 looks like this:

MatcherConcept Conceptual type that outlines the common properties of all UTF Matchers.
unicode A single entry point to lookup Unicode code point sets by name or alias of a block, script or general category.

Enums

Name Description
NormalizationForm Enumeration type for normalization forms, passed as template parameter for functions like normalize.
UnicodeDecomposition Unicode character decomposition type.

Templates

Name Description
codepointSetTrie A shorthand for creating a custom multi-level fixed Trie from a CodepointSet. sizes are numbers of bits per level, with the most significant bits used first.
codepointTrie A slightly more general tool for building fixed Trie for the Unicode data.
isCodepointSet Tests if T is some kind a set of code points. Intended for template constraints.

Enum values

Name Type Description
isIntegralPair Tests if T is a pair of integers that implicitly convert to V. The following code must compile for any pair T:
isUtfMatcher Test if M is an UTF Matcher for ranges of Char.
lineSep Constant code point (0x2028) - line separator.
nelSep Constant code point (0x0085) - next line.
NFC Shorthand aliases from values indicating normalization forms.
NFD Shorthand aliases from values indicating normalization forms.
NFKC Shorthand aliases from values indicating normalization forms.
NFKD Shorthand aliases from values indicating normalization forms.
paraSep Constant code point (0x2029) - paragraph separator.

Aliases

Name Type Description
CodepointSet std.uni The recommended default type for set of code points. For details, see the current implementation: InversionList.
CodepointSetTrie typeof(TrieBuilder!(bool,dchar,lastDchar+1,Prefix)(false).build()) Type of Trie generated by codepointSetTrie function.
CodepointTrie typeof(TrieBuilder!(T,dchar,lastDchar+1,Prefix)(T.init).build()) Type of Trie as generated by codepointTrie function.

Authors

Dmitry Olshansky

License

Boost License 1.0.

Comments