SWI-Prolog -- library(unicode): Unicode string handling

This library is a wrapper around the utf8proc library, providing information about Unicode code-points and performing operations (mappings) on Unicode atoms. The central predicate is unicode_map/3, mapping a Unicode atom to another Unicode atom using a sequence of operations. The predicates unicode_nfd/2, unicode_nfc/2, unicode_nfkd/2 and unicode_nfkc/2 implement the four standard Unicode normalization forms.

Lump handling:

U+0020      <-- all space characters (general category Zs)
U+0027  '   <-- left/right single quotation mark U+2018..2019,
                modifier letter apostrophe U+02BC,
                modifier letter vertical line U+02C8
U+002D  -   <-- all dash characters (general category Pd),
                minus U+2212
U+002F  /   <-- fraction slash U+2044,
                division slash U+2215
U+003A  :   <-- ratio U+2236
U+003C  <   <-- single left-pointing angle quotation mark U+2039,
                left-pointing angle bracket U+2329,
                left angle bracket U+3008
U+003E  >   <-- single right-pointing angle quotation mark U+203A,
                right-pointing angle bracket U+232A,
                right angle bracket U+3009
U+005C  \   <-- set minus U+2216
U+005E  ^   <-- modifier letter up arrowhead U+02C4,
                modifier letter circumflex accent U+02C6,
                caret U+2038,
                up arrowhead U+2303
U+005F  _   <-- all connector characters (general category Pc),
                modifier letter low macron U+02CD
U+0060  `   <-- modifier letter grave accent U+02CB
U+007C  |   <-- divides U+2223
U+007E  ~   <-- tilde operator U+223C

[det]unicode_map(+In, -Out, +Options)

Perform unicode normalization operations. Options is a list of operations. Defined operations are:

stable: Unicode Versioning Stability has to be respected.
compat: Compatiblity decomposition (i.e. formatting information is lost)
compose: Return a result with composed characters.
decompose: Return a result with decomposed characters.
ignore: Strip "default ignorable characters"
rejectna: Return an error, if the input contains unassigned code points.
nlf2ls: Indicating that NLF-sequences (LF, CRLF, CR, NEL) are representing a line break, and should be converted to the unicode character for line separation (LS).
nlf2ps: Indicating that NLF-sequences are representing a paragraph break, and should be converted to the unicode character for paragraph separation (PS).
nlf2lf: Indicating that the meaning of NLF-sequences is unknown.
stripcc: Strips and/or convers control characters. NLF-sequences are transformed into space, except if one of the NLF2LS/PS/LF options is given. HorizontalTab (HT) and FormFeed (FF) are treated as a NLF-sequence in this case. All other control characters are simply removed.
casefold: Performs unicode case folding, to be able to do a case-insensitive string comparison.
charbound: Inserts 0xFF bytes at the beginning of each sequence which is representing a single grapheme cluster (see UAX#29).
lump: (e.g. HYPHEN U+2010 and MINUS U+2212 to ASCII "-"). (See module header for details.) If NLF2LF is set, this includes a transformation of paragraph and line separators to ASCII line-feed (LF).
stripmark: Strips all character markings (non-spacing, spacing and enclosing) (i.e. accents) NOTE: this option works only with compose or decompose.

[det]unicode_nfd(+In, -Out)

Characters are decomposed by canonical equivalence.

[det]unicode_nfc(+In, -Out)

Characters are decomposed and then recomposed by canonical equivalence. It is possible for the result to be a different sequence of characters than the original.

See also: http://en.wikipedia.org/wiki/Unicode_equivalence\#Normal_forms

[det]unicode_nfkd(+In, -Out)

Characters are decomposed by compatibility equivalence.

[det]unicode_nfkc(+In, -Out)

Characters are decomposed by compatibility equivalence, then recomposed by canonical equivalence.

[nondet]unicode_property(?Char, ?Property)

True if Property is defined for Char. Property is a term Name(Value). Defined property-names are:

category(atom)

Unicode code category of Char. This is one of Cc, Cf, Cn, Co, Cs, Ll, Lm, Lo, Lt, Lu, Mc, Me, Mn, Nd, Nl, No, Pc, Pd, Pe, Pf, Pi, Po, Ps, Sc, Sk, Sm, So, Zl, Zp, Zs. When testing, a single letter stands for all its subcategories. E.g. to test form a letter, you can use

unicode_property(C, category('L'))

combining_class(integer)

bidi_class(atom)

decomp_type(atom)

decomp_mapping(list(code))

bidi_mirrored(bool)

uppercase_mapping(code)

lowercase_mapping(code)

titlecase_mapping(code)

comb1st_index(code)

comb2nd_index(code)

comp_exclusion(bool)

ignorable(bool)

control_boundary(bool)

extend(bool)

casefold_mapping(list(code))

To be done: Complete documentation

1 library(unicode): Unicode string handling