rishi/scryer-prolog
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Work in progress: add char_utf8bytes (#493)

Browse Source 
* Add char_utf8bytes to library

* Improved implementation

* Improve code + add chars predicate

* Update example

* Renamed string_utf8bytes to char_utf8bytes
This commit is contained in:
Matthieu Wipliez
2020-05-15 18:05:04 +02:00
committed by GitHub
parent b60561c3bb
commit df06d4b9a2
2 changed files with 44 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
src/prolog/lib/charsio.pl
View File

@@ -1,10 +1,13 @@
:- module(charsio, [char_type/2, get_single_char/1,
:- module(charsio, [char_type/2,
chars_utf8bytes/2,
get_single_char/1,
read_term_from_chars/2,
write_term_to_chars/3]).
:- use_module(library(dcgs)).
:- use_module(library(iso_ext)).
:- use_module(library(error)).
:- use_module(library(lists), [append/3]).
:- use_module(library(lists)).
fabricate_var_name(VarType, VarName, N) :-
char_code('A', AC),
@@ -135,3 +138,27 @@ write_term_to_chars(Term, Options, Chars) :-
term_variables(Term, Vars),
extend_var_list(Vars, VNNames, NewVarNames, numbervars),
'$write_term_to_chars'(Chars, Term, IgnoreOps, NumberVars, Quoted, NewVarNames, MaxDepth).
% Encodes Ch character to list of Bytes.
% TODO: if Ch is variable, decode Bytes to Char.
char_utf8bytes(Ch, Bytes) :-
char_code(Ch, Code),
phrase(code_to_utf8(Code), Bytes).
code_to_utf8(Code) --> {Code @< 0x80}, [Code], !.
code_to_utf8(Code) --> {Code @< 0x800}, encode(Code, 0xC0, 2), !.
code_to_utf8(Code) --> {Code @< 0x10000}, encode(Code, 0xE0, 3), !.
code_to_utf8(Code) --> {Code @< 0x110000}, encode(Code, 0xF0, 4), !.
encode(_, _, 0) --> !.
encode(Code, Prefix, Nb) -->
{ Nb1 is Nb - 1, Byte is Prefix \/ ((Code >> (6 * Nb1)) /\ 0x3F) },
[Byte], encode(Code, 0x80, Nb1).
% Encodes a list of characters Cs to a list of UTF-8 bytes Bs.
% TODO: if Cs is variable, decode bytes to chars instead.
chars_utf8bytes(Cs, Bs) :-
must_be(list, Cs),
maplist(must_be(atom), Cs),
maplist(char_utf8bytes, Cs, Bss),
append(Bss, Bs).