unicode.pl

/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (c)  2010-2020, University of Amsterdam
                              CWI, Amsterdam
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*/

:- module(unicode,
          [ unicode_property/2,         % ?Code, ?Property
            unicode_map/3,              % +In, -Out, +Options
            unicode_nfd/2,              % +In, -Out
            unicode_nfc/2,              % +In, -Out
            unicode_nfkd/2,             % +In, -Out
            unicode_nfkc/2              % +In, -Out
          ]).
:- use_foreign_library(foreign(unicode4pl)).

/** <module> Unicode string handling

This       library       is       a       wrapper       around       the
[[utf8proc][http://www.public-software-group.org/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
==

@see http://www.public-software-group.org/utf8proc
*/

system:goal_expansion(unicode_map(In, Out, Options),
                      unicode_map(In, Out, Mask)) :-
    is_list(Options),
    unicode_option_mask(Options, Mask).

%!  unicode_map(+In, -Out, +Options) is det.
%
%   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=.

%!  unicode_nfd(+In, -Out) is det.
%
%   Characters are decomposed by canonical equivalence.

unicode_nfd(In, Out) :-
    unicode_map(In, Out, [stable,decompose]).

%!  unicode_nfc(+In, -Out) is det.
%
%   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 http://en.wikipedia.org/wiki/Unicode_equivalence#Normal_forms

unicode_nfc(In, Out) :-
    unicode_map(In, Out, [stable,compose]).

%!  unicode_nfkd(+In, -Out) is det.
%
%   Characters are decomposed by compatibility equivalence.

unicode_nfkd(In, Out) :-
    unicode_map(In, Out, [stable,decompose,compat]).

%!  unicode_nfkc(+In, -Out) is det.
%
%   Characters are decomposed  by   compatibility  equivalence, then
%   recomposed by canonical equivalence.

unicode_nfkc(In, Out) :-
    unicode_map(In, Out, [stable,compose,compat]).


%!  unicode_property(?Char, ?Property) is nondet.
%
%   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))
%
%   @tbd Complete documentation

unicode_property(Code, Property) :-
    nonvar(Code), nonvar(Property),
    !,
    '$unicode_property'(Code, Property).
unicode_property(Code, Property) :-
    nonvar(Code),
    !,
    property(Property),
    '$unicode_property'(Code, Property).
unicode_property(Code, Property) :-
    var(Code),
    !,
    between(0, 0x10ffff, Code),
    property(Property),
    '$unicode_property'(Code, Property).

property(category(_)).
property(combining_class(_)).
property(bidi_class(_)).
property(decomp_type(_)).
property(decomp_mapping(_)).
property(bidi_mirrored(_)).
property(uppercase_mapping(_)).
property(lowercase_mapping(_)).
property(titlecase_mapping(_)).
property(comb1st_index(_)).
property(comb2nd_index(_)).
property(comp_exclusion(_)).
property(ignorable(_)).
property(control_boundary(_)).
property(extend(_)).
property(casefold_mapping(_)).