1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2014-2024, VU University Amsterdam 7 CWI, Amsterdam 8 SWI-Prolog Solutions b.v. 9 All rights reserved. 10 11 Redistribution and use in source and binary forms, with or without 12 modification, are permitted provided that the following conditions 13 are met: 14 15 1. Redistributions of source code must retain the above copyright 16 notice, this list of conditions and the following disclaimer. 17 18 2. Redistributions in binary form must reproduce the above copyright 19 notice, this list of conditions and the following disclaimer in 20 the documentation and/or other materials provided with the 21 distribution. 22 23 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 24 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 25 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 26 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 27 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 28 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 29 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 30 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 31 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 33 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 34 POSSIBILITY OF SUCH DAMAGE. 35*/ 36 37:- module(pengines_io, 38 [ pengine_writeln/1, % +Term 39 pengine_nl/0, 40 pengine_tab/1, 41 pengine_flush_output/0, 42 pengine_format/1, % +Format 43 pengine_format/2, % +Format, +Args 44 45 pengine_write_term/2, % +Term, +Options 46 pengine_write/1, % +Term 47 pengine_writeq/1, % +Term 48 pengine_display/1, % +Term 49 pengine_print/1, % +Term 50 pengine_write_canonical/1, % +Term 51 52 pengine_listing/0, 53 pengine_listing/1, % +Spec 54 pengine_portray_clause/1, % +Term 55 56 pengine_read/1, % -Term 57 pengine_read_line_to_string/2, % +Stream, -LineAsString 58 pengine_read_line_to_codes/2, % +Stream, -LineAsCodes 59 60 pengine_io_predicate/1, % ?Head 61 pengine_bind_io_to_html/1, % +Module 62 pengine_io_goal_expansion/2,% +Goal, -Expanded 63 64 message_lines_to_html/3 % +Lines, +Classes, -HTML 65 ]). 66:- autoload(library(apply),[foldl/4,maplist/3,maplist/4]). 67:- autoload(library(backcomp),[thread_at_exit/1]). 68:- use_module(library(debug),[assertion/1]). 69:- autoload(library(error),[must_be/2]). 70:- autoload(library(listing),[listing/1,portray_clause/1]). 71:- autoload(library(lists),[append/2,append/3,subtract/3]). 72:- autoload(library(option),[option/3,merge_options/3]). 73:- autoload(library(pengines), 74 [ pengine_self/1, 75 pengine_output/1, 76 pengine_input/2, 77 pengine_property/2 78 ]). 79:- autoload(library(prolog_stream),[open_prolog_stream/4]). 80:- autoload(library(readutil),[read_line_to_string/2]). 81:- autoload(library(http/term_html),[term/4]). 82 83:- use_module(library(yall),[(>>)/4]). 84:- use_module(library(http/html_write),[html/3,print_html/1, op(_,_,_)]). 85:- use_module(library(settings),[setting/4,setting/2]). 86 87:- use_module(library(sandbox), []). 88:- autoload(library(thread), [call_in_thread/2]). 89 90:- html_meta send_html(). 91:- public send_html/1. 92 93:- meta_predicate 94 pengine_format(,).
129:- setting(write_options, list(any), [max_depth(1000)], 130 'Additional options for stringifying Prolog results'). 131 132 133 /******************************* 134 * OUTPUT * 135 *******************************/
141pengine_writeln(Term) :- 142 pengine_output, 143 !, 144 pengine_module(Module), 145 send_html(span(class(writeln), 146 [ \term(Term, 147 [ module(Module) 148 ]), 149 br([]) 150 ])). 151pengine_writeln(Term) :- 152 writeln(Term).
158pengine_nl :- 159 pengine_output, 160 !, 161 send_html(br([])). 162pengine_nl :- 163 nl.
169pengine_tab(Expr) :- 170 pengine_output, 171 !, 172 N is Expr, 173 length(List, N), 174 maplist(=(&(nbsp)), List), 175 send_html(List). 176pengine_tab(N) :- 177 tab(N).
185pengine_flush_output :- 186 pengine_output, 187 \+ pengine_io(_,_), 188 !. 189pengine_flush_output :- 190 flush_output. 191 192:- multifile 193 pengines:pengine_flush_output_hook/0. 194 195penginespengine_flush_output_hook :- 196 pengine_flush_output.
write.206pengine_write_term(Term, Options) :- 207 pengine_output, 208 !, 209 option(class(Class), Options, write), 210 pengine_module(Module), 211 send_html(span(class(Class), \term(Term,[module(Module)|Options]))). 212pengine_write_term(Term, Options) :- 213 write_term(Term, Options).
223pengine_write(Term) :- 224 pengine_write_term(Term, [numbervars(true)]). 225pengine_writeq(Term) :- 226 pengine_write_term(Term, [quoted(true), numbervars(true)]). 227pengine_display(Term) :- 228 pengine_write_term(Term, [quoted(true), ignore_ops(true)]). 229pengine_print(Term) :- 230 current_prolog_flag(print_write_options, Options), 231 pengine_write_term(Term, Options). 232pengine_write_canonical(Term) :- 233 pengine_output, 234 !, 235 with_output_to(string(String), write_canonical(Term)), 236 send_html(span(class([write, cononical]), String)). 237pengine_write_canonical(Term) :- 238 write_canonical(Term).
248pengine_format(Format) :- 249 pengine_format(Format, []). 250pengine_format(Format, Args) :- 251 pengine_output, 252 !, 253 format(string(String), Format, Args), 254 split_string(String, "\n", "", Lines), 255 send_html(\lines(Lines, format)). 256pengine_format(Format, Args) :- 257 format(Format, Args). 258 259 260 /******************************* 261 * LISTING * 262 *******************************/
270pengine_listing :- 271 pengine_listing(_). 272 273pengine_listing(Spec) :- 274 pengine_self(Module), 275 with_output_to(string(String), listing(Module:Spec)), 276 split_string(String, "", "\n", [Pre]), 277 send_html(pre(class(listing), Pre)). 278 279pengine_portray_clause(Term) :- 280 pengine_output, 281 !, 282 with_output_to(string(String), portray_clause(Term)), 283 split_string(String, "", "\n", [Pre]), 284 send_html(pre(class(listing), Pre)). 285pengine_portray_clause(Term) :- 286 portray_clause(Term). 287 288 289 /******************************* 290 * PRINT MESSAGE * 291 *******************************/ 292 293:- multifile user:message_hook/3.
300user:message_hook(Term, Kind, Lines) :-
301 Kind \== silent,
302 pengine_self(_),
303 atom_concat('msg-', Kind, Class),
304 message_lines_to_html(Lines, [Class], HTMlString),
305 ( source_location(File, Line)
306 -> Src = File:Line
307 ; Src = (-)
308 ),
309 pengine_output(message(Term, Kind, HTMlString, Src)).'prolog-message' and the given Classes.317message_lines_to_html(Lines, Classes, HTMlString) :- 318 phrase(html(pre(class(['prolog-message'|Classes]), 319 \message_lines(Lines))), Tokens), 320 with_output_to(string(HTMlString), print_html(Tokens)). 321 322message_lines([]) --> 323 !. 324message_lines([nl|T]) --> 325 !, 326 html('\n'), % we are in a <pre> environment 327 message_lines(T). 328message_lines([flush]) --> 329 !. 330message_lines([ansi(Attributes, Fmt, Args)|T]) --> 331 !, 332 { is_list(Attributes) 333 -> foldl(style, Attributes, Fmt-Args, HTML) 334 ; style(Attributes, Fmt-Args, HTML) 335 }, 336 html(HTML), 337 message_lines(T). 338message_lines([url(Pos)|T]) --> 339 !, 340 location(Pos), 341 message_lines(T). 342message_lines([url(HREF, Label)|T]) --> 343 !, 344 html(a(href(HREF),Label)), 345 message_lines(T). 346message_lines([H|T]) --> 347 html(H), 348 message_lines(T). 349 350location(File:Line:Column) --> 351 !, 352 html([File, :, Line, :, Column]). 353location(File:Line) --> 354 !, 355 html([File, :, Line]). 356location(File) --> 357 html([File]). 358 359style(bold, Content, b(Content)) :- !. 360style(fg(default), Content, span(style('color: black'), Content)) :- !. 361style(fg(Color), Content, span(style('color:'+Color), Content)) :- !. 362style(_, Content, Content). 363 364 365 /******************************* 366 * INPUT * 367 *******************************/ 368 369pengine_read(Term) :- 370 pengine_input, 371 !, 372 prompt(Prompt, Prompt), 373 pengine_input(Prompt, Term). 374pengine_read(Term) :- 375 read(Term). 376 377pengine_read_line_to_string(From, String) :- 378 pengine_input, 379 !, 380 must_be(oneof([current_input,user_input]), From), 381 ( prompt(Prompt, Prompt), 382 Prompt \== '' 383 -> true 384 ; Prompt = 'line> ' 385 ), 386 pengine_input(_{type: console, prompt:Prompt}, StringNL), 387 string_concat(String, "\n", StringNL). 388pengine_read_line_to_string(From, String) :- 389 read_line_to_string(From, String). 390 391pengine_read_line_to_codes(From, Codes) :- 392 pengine_read_line_to_string(From, String), 393 string_codes(String, Codes). 394 395 396 /******************************* 397 * HTML * 398 *******************************/ 399 400lines([], _) --> []. 401lines([H|T], Class) --> 402 html(span(class(Class), H)), 403 ( { T == [] } 404 -> [] 405 ; html(br([])), 406 lines(T, Class) 407 ).
414send_html(HTML) :-
415 phrase(html(HTML), Tokens),
416 with_output_to(string(HTMlString), print_html(Tokens)),
417 pengine_output(HTMlString).424pengine_module(Module) :- 425 pengine_self(Pengine), 426 !, 427 pengine_property(Pengine, module(Module)). 428pengine_module(user). 429 430 /******************************* 431 * OUTPUT FORMAT * 432 *******************************/
461:- multifile
462 pengines:event_to_json/3.'json-s' or 'json-html', emit a simplified
JSON representation of the data, suitable for notably SWISH.
This deals with Prolog answers and output messages. If a message
originates from print_message/3, it gets several additional
properties:
error, warning,
etc.)479penginesevent_to_json(success(ID, Answers0, Projection, Time, More), JSON, 480 'json-s') :- 481 !, 482 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 483 maplist(answer_to_json_strings(ID), Answers0, Answers), 484 add_projection(Projection, JSON0, JSON). 485penginesevent_to_json(output(ID, Term), JSON, 'json-s') :- 486 !, 487 map_output(ID, Term, JSON). 488 489add_projection([], JSON, JSON) :- !. 490add_projection(VarNames, JSON0, JSON0.put(projection, VarNames)).
498answer_to_json_strings(Pengine, DictIn, DictOut) :- 499 dict_pairs(DictIn, Tag, Pairs), 500 maplist(term_string_value(Pengine), Pairs, BindingsOut), 501 dict_pairs(DictOut, Tag, BindingsOut). 502 503term_string_value(Pengine, N-V, N-A) :- 504 with_output_to(string(A), 505 write_term(V, 506 [ module(Pengine), 507 quoted(true) 508 ])).
json-html format. This
format represents the answer as JSON, but the variable bindings are
(structured) HTML strings rather than JSON objects.
CHR residual goals are not bound to the projection variables. We hacked a bypass to fetch these by returning them in a variable named _residuals, which must be bound to a term '$residuals'(List). Such a variable is removed from the projection and added to residual goals.
522penginesevent_to_json(success(ID, Answers0, Projection, Time, More), 523 JSON, 'json-html') :- 524 !, 525 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 526 maplist(map_answer(ID), Answers0, ResVars, Answers), 527 add_projection(Projection, ResVars, JSON0, JSON). 528penginesevent_to_json(output(ID, Term), JSON, 'json-html') :- 529 !, 530 map_output(ID, Term, JSON). 531 532map_answer(ID, Bindings0, ResVars, Answer) :- 533 dict_bindings(Bindings0, Bindings1), 534 select_residuals(Bindings1, Bindings2, ResVars, Residuals0, Clauses), 535 append(Residuals0, Residuals1), 536 prolog:translate_bindings(Bindings2, Bindings3, [], Residuals1, 537 ID:Residuals-_HiddenResiduals), 538 maplist(binding_to_html(ID), Bindings3, VarBindings), 539 final_answer(ID, VarBindings, Residuals, Clauses, Answer). 540 541final_answer(_Id, VarBindings, [], [], Answer) :- 542 !, 543 Answer = json{variables:VarBindings}. 544final_answer(ID, VarBindings, Residuals, [], Answer) :- 545 !, 546 residuals_html(Residuals, ID, ResHTML), 547 Answer = json{variables:VarBindings, residuals:ResHTML}. 548final_answer(ID, VarBindings, [], Clauses, Answer) :- 549 !, 550 clauses_html(Clauses, ID, ClausesHTML), 551 Answer = json{variables:VarBindings, wfs_residual_program:ClausesHTML}. 552final_answer(ID, VarBindings, Residuals, Clauses, Answer) :- 553 !, 554 residuals_html(Residuals, ID, ResHTML), 555 clauses_html(Clauses, ID, ClausesHTML), 556 Answer = json{variables:VarBindings, 557 residuals:ResHTML, 558 wfs_residual_program:ClausesHTML}. 559 560residuals_html([], _, []). 561residuals_html([H0|T0], Module, [H|T]) :- 562 term_html_string(H0, [], Module, H, [priority(999)]), 563 residuals_html(T0, Module, T). 564 565clauses_html(Clauses, _ID, HTMLString) :- 566 with_output_to(string(Program), list_clauses(Clauses)), 567 phrase(html(pre([class('wfs-residual-program')], Program)), Tokens), 568 with_output_to(string(HTMLString), print_html(Tokens)). 569 570list_clauses([]). 571list_clauses([H|T]) :- 572 ( system_undefined(H) 573 -> true 574 ; portray_clause(H) 575 ), 576 list_clauses(T). 577 578system_undefined((undefined :- tnot(undefined))). 579system_undefined((answer_count_restraint :- tnot(answer_count_restraint))). 580system_undefined((radial_restraint :- tnot(radial_restraint))). 581 582dict_bindings(Dict, Bindings) :- 583 dict_pairs(Dict, _Tag, Pairs), 584 maplist([N-V,N=V]>>true, Pairs, Bindings). 585 586select_residuals([], [], [], [], []). 587select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 588 binding_residual(H, Var, Residual), 589 !, 590 Vars = [Var|TV], 591 Residuals = [Residual|TR], 592 select_residuals(T, Bindings, TV, TR, Clauses). 593select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 594 binding_residual_clauses(H, Var, Delays, Clauses0), 595 !, 596 Vars = [Var|TV], 597 Residuals = [Delays|TR], 598 append(Clauses0, CT, Clauses), 599 select_residuals(T, Bindings, TV, TR, CT). 600select_residuals([H|T0], [H|T], Vars, Residuals, Clauses) :- 601 select_residuals(T0, T, Vars, Residuals, Clauses). 602 603binding_residual('_residuals' = '$residuals'(Residuals), '_residuals', Residuals) :- 604 is_list(Residuals). 605binding_residual('Residuals' = '$residuals'(Residuals), 'Residuals', Residuals) :- 606 is_list(Residuals). 607binding_residual('Residual' = '$residual'(Residual), 'Residual', [Residual]) :- 608 callable(Residual). 609 610binding_residual_clauses( 611 '_wfs_residual_program' = '$wfs_residual_program'(Delays, Clauses), 612 '_wfs_residual_program', Residuals, Clauses) :- 613 phrase(delay_list(Delays), Residuals). 614 615delay_list(true) --> !. 616delay_list((A,B)) --> !, delay_list(A), delay_list(B). 617delay_list(M:A) --> !, [M:'$wfs_undefined'(A)]. 618delay_list(A) --> ['$wfs_undefined'(A)]. 619 620add_projection(-, _, JSON, JSON) :- !. 621add_projection(VarNames0, ResVars0, JSON0, JSON) :- 622 append(ResVars0, ResVars1), 623 sort(ResVars1, ResVars), 624 subtract(VarNames0, ResVars, VarNames), 625 add_projection(VarNames, JSON0, JSON).
636binding_to_html(ID, binding(Vars,Term,Substitutions), JSON) :- 637 JSON0 = json{variables:Vars, value:HTMLString}, 638 binding_write_options(ID, Options), 639 term_html_string(Term, Vars, ID, HTMLString, Options), 640 ( Substitutions == [] 641 -> JSON = JSON0 642 ; maplist(subst_to_html(ID), Substitutions, HTMLSubst), 643 JSON = JSON0.put(substitutions, HTMLSubst) 644 ). 645 646binding_write_options(Pengine, Options) :- 647 ( current_predicate(Pengine:screen_property/1), 648 Pengine:screen_property(tabled(true)) 649 -> Options = [] 650 ; Options = [priority(699)] 651 ).
660term_html_string(Term, Vars, Module, HTMLString, Options) :-
661 setting(write_options, WOptions),
662 merge_options(WOptions,
663 [ quoted(true),
664 numbervars(true),
665 module(Module)
666 | Options
667 ], WriteOptions),
668 phrase(term_html(Term, Vars, WriteOptions), Tokens),
669 with_output_to(string(HTMLString), print_html(Tokens)).681:- multifile binding_term//3. 682 683term_html(Term, Vars, WriteOptions) --> 684 { nonvar(Term) }, 685 binding_term(Term, Vars, WriteOptions), 686 !. 687term_html(Undef, _Vars, WriteOptions) --> 688 { nonvar(Undef), 689 Undef = '$wfs_undefined'(Term), 690 ! 691 }, 692 html(span(class(wfs_undefined), \term(Term, WriteOptions))). 693term_html(Term, _Vars, WriteOptions) --> 694 term(Term, WriteOptions).
701subst_to_html(ID, '$VAR'(Name)=Value, json{var:Name, value:HTMLString}) :- 702 !, 703 binding_write_options(ID, Options), 704 term_html_string(Value, [Name], ID, HTMLString, Options). 705subst_to_html(_, Term, _) :- 706 assertion(Term = '$VAR'(_)).
713map_output(ID, message(Term, Kind, HTMLString, Src), JSON) :- 714 atomic(HTMLString), 715 !, 716 JSON0 = json{event:output, id:ID, message:Kind, data:HTMLString}, 717 pengines:add_error_details(Term, JSON0, JSON1), 718 ( Src = File:Line, 719 \+ JSON1.get(location) = _ 720 -> JSON = JSON1.put(_{location:_{file:File, line:Line}}) 721 ; JSON = JSON1 722 ). 723map_output(ID, Term, json{event:output, id:ID, data:Data}) :- 724 ( atomic(Term) 725 -> Data = Term 726 ; is_dict(Term, json), 727 ground(json) % TBD: Check proper JSON object? 728 -> Data = Term 729 ; term_string(Term, Data) 730 ).
737:- multifile 738 prolog_help:show_html_hook/1. 739 740prolog_helpshow_html_hook(HTML) :- 741 pengine_output, 742 pengine_output(HTML). 743 744 745 /******************************* 746 * SANDBOXING * 747 *******************************/ 748 749:- multifile 750 sandbox:safe_primitive/1, % Goal 751 sandbox:safe_meta/2. % Goal, Called 752 753sandbox:safe_primitive(pengines_io:pengine_listing(_)). 754sandbox:safe_primitive(pengines_io:pengine_nl). 755sandbox:safe_primitive(pengines_io:pengine_tab(_)). 756sandbox:safe_primitive(pengines_io:pengine_flush_output). 757sandbox:safe_primitive(pengines_io:pengine_print(_)). 758sandbox:safe_primitive(pengines_io:pengine_write(_)). 759sandbox:safe_primitive(pengines_io:pengine_read(_)). 760sandbox:safe_primitive(pengines_io:pengine_read_line_to_string(_,_)). 761sandbox:safe_primitive(pengines_io:pengine_read_line_to_codes(_,_)). 762sandbox:safe_primitive(pengines_io:pengine_write_canonical(_)). 763sandbox:safe_primitive(pengines_io:pengine_write_term(_,_)). 764sandbox:safe_primitive(pengines_io:pengine_writeln(_)). 765sandbox:safe_primitive(pengines_io:pengine_writeq(_)). 766sandbox:safe_primitive(pengines_io:pengine_portray_clause(_)). 767sandbox:safe_primitive(system:write_term(_,_)). 768sandbox:safe_primitive(system:prompt(_,_)). 769sandbox:safe_primitive(system:statistics(_,_)). 770sandbox:safe_primitive(system:put_code(_)). 771sandbox:safe_primitive(system:put_char(_)). 772 773sandbox:safe_meta(pengines_io:pengine_format(Format, Args), Calls) :- 774 sandbox:format_calls(Format, Args, Calls). 775 776 777 /******************************* 778 * REDEFINITION * 779 *******************************/
786pengine_io_predicate(writeln(_)). 787pengine_io_predicate(nl). 788pengine_io_predicate(tab(_)). 789pengine_io_predicate(flush_output). 790pengine_io_predicate(format(_)). 791pengine_io_predicate(format(_,_)). 792pengine_io_predicate(read(_)). 793pengine_io_predicate(read_line_to_string(_,_)). 794pengine_io_predicate(read_line_to_codes(_,_)). 795pengine_io_predicate(write_term(_,_)). 796pengine_io_predicate(write(_)). 797pengine_io_predicate(writeq(_)). 798pengine_io_predicate(display(_)). 799pengine_io_predicate(print(_)). 800pengine_io_predicate(write_canonical(_)). 801pengine_io_predicate(listing). 802pengine_io_predicate(listing(_)). 803pengine_io_predicate(portray_clause(_)). 804 805term_expansion(pengine_io_goal_expansion(_,_), 806 Clauses) :- 807 findall(Clause, io_mapping(Clause), Clauses). 808 809io_mapping(pengine_io_goal_expansion(Head, Mapped)) :- 810 pengine_io_predicate(Head), 811 Head =.. [Name|Args], 812 atom_concat(pengine_, Name, BodyName), 813 Mapped =.. [BodyName|Args]. 814 815pengine_io_goal_expansion(_, _). 816 817 818 /******************************* 819 * REBIND PENGINE I/O * 820 *******************************/ 821 822:- public 823 stream_write/2, 824 stream_read/2, 825 stream_close/1. 826 827:- thread_local 828 pengine_io/2. 829 830stream_write(Stream, Out) :- 831 ( pengine_io(_,_) 832 -> send_html(pre(class(console), Out)) 833 ; current_prolog_flag(pengine_main_thread, TID), 834 thread_signal(TID, stream_write(Stream, Out)) 835 ). 836stream_read(Stream, Data) :- 837 ( pengine_io(_,_) 838 -> prompt(Prompt, Prompt), 839 pengine_input(_{type:console, prompt:Prompt}, Data) 840 ; current_prolog_flag(pengine_main_thread, TID), 841 call_in_thread(TID, stream_read(Stream, Data)) 842 ). 843stream_close(_Stream).
853pengine_bind_user_streams :- 854 Err = Out, 855 open_prolog_stream(pengines_io, write, Out, []), 856 set_stream(Out, buffer(line)), 857 open_prolog_stream(pengines_io, read, In, []), 858 set_stream(In, alias(user_input)), 859 set_stream(Out, alias(user_output)), 860 set_stream(Err, alias(user_error)), 861 set_stream(In, alias(current_input)), 862 set_stream(Out, alias(current_output)), 863 assertz(pengine_io(In, Out)), 864 thread_self(Me), 865 thread_property(Me, id(Id)), 866 set_prolog_flag(pengine_main_thread, Id), 867 thread_at_exit(close_io). 868 869close_io :- 870 retract(pengine_io(In, Out)), 871 !, 872 close(In, [force(true)]), 873 close(Out, [force(true)]). 874close_io.
881pengine_output :- 882 current_output(Out), 883 pengine_io(_, Out). 884 885pengine_input :- 886 current_input(In), 887 pengine_io(In, _).
895pengine_bind_io_to_html(Module) :- 896 forall(pengine_io_predicate(Head), 897 bind_io(Head, Module)), 898 pengine_bind_user_streams. 899 900bind_io(Head, Module) :- 901 prompt(_, ''), 902 redefine_system_predicate(Module:Head), 903 functor(Head, Name, Arity), 904 Head =.. [Name|Args], 905 atom_concat(pengine_, Name, BodyName), 906 Body =.. [BodyName|Args], 907 assertz(Module:(Head :- Body)), 908 compile_predicates([Module:Name/Arity])
Provide Prolog I/O for HTML clients
This module redefines some of the standard Prolog I/O predicates to behave transparently for HTML clients. It provides two ways to redefine the standard predicates: using goal_expansion/2 and by redefining the system predicates using redefine_system_predicate/1. The latter is the preferred route because it gives a more predictable trace to the user and works regardless of the use of other expansion and meta-calling.
Redefining works by redefining the system predicates in the context of the pengine's module. This is configured using the following code snippet.
:- pengine_application(myapp). :- use_module(myapp:library(pengines_io)). pengines:prepare_module(Module, myapp, _Options) :- pengines_io:pengine_bind_io_to_html(Module).Using goal_expansion/2 works by rewriting the corresponding goals using goal_expansion/2 and use the new definition to re-route I/O via pengine_input/2 and pengine_output/1. A pengine application is prepared for using this module with the following code:
:- pengine_application(myapp). :- use_module(myapp:library(pengines_io)). myapp:goal_expansion(In,Out) :- pengine_io_goal_expansion(In, Out).*/