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) 2014-2019, VU University Amsterdam 7 CWI, Amsterdam 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 17 2. Redistributions in binary form must reproduce the above copyright 18 notice, this list of conditions and the following disclaimer in 19 the documentation and/or other materials provided with the 20 distribution. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 30 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 32 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 POSSIBILITY OF SUCH DAMAGE. 34*/ 35 36:- module(pengines_io, 37 [ pengine_writeln/1, % +Term 38 pengine_nl/0, 39 pengine_tab/1, 40 pengine_flush_output/0, 41 pengine_format/1, % +Format 42 pengine_format/2, % +Format, +Args 43 44 pengine_write_term/2, % +Term, +Options 45 pengine_write/1, % +Term 46 pengine_writeq/1, % +Term 47 pengine_display/1, % +Term 48 pengine_print/1, % +Term 49 pengine_write_canonical/1, % +Term 50 51 pengine_listing/0, 52 pengine_listing/1, % +Spec 53 pengine_portray_clause/1, % +Term 54 55 pengine_read/1, % -Term 56 pengine_read_line_to_string/2, % +Stream, -LineAsString 57 pengine_read_line_to_codes/2, % +Stream, -LineAsCodes 58 59 pengine_io_predicate/1, % ?Head 60 pengine_bind_io_to_html/1, % +Module 61 pengine_io_goal_expansion/2,% +Goal, -Expanded 62 63 message_lines_to_html/3 % +Lines, +Classes, -HTML 64 ]). 65:- autoload(library(apply),[foldl/4,maplist/3,maplist/4]). 66:- autoload(library(backcomp),[thread_at_exit/1]). 67:- autoload(library(debug),[assertion/1]). 68:- autoload(library(error),[must_be/2]). 69:- autoload(library(listing),[listing/1,portray_clause/1]). 70:- autoload(library(lists),[append/2,append/3,subtract/3]). 71:- autoload(library(option),[option/3,merge_options/3]). 72:- autoload(library(pengines), 73 [ pengine_self/1, 74 pengine_output/1, 75 pengine_input/2, 76 pengine_property/2 77 ]). 78:- autoload(library(prolog_stream),[open_prolog_stream/4]). 79:- autoload(library(readutil),[read_line_to_string/2]). 80:- autoload(library(yall),[(>>)/4]). 81:- autoload(library(http/term_html),[term/4]). 82 83:- use_module(library(http/html_write),[html/3,print_html/1, op(_,_,_)]). 84:- use_module(library(settings),[setting/4,setting/2]). 85 86:- use_module(library(sandbox), []). 87:- autoload(library(thread), [call_in_thread/2]). 88 89:- html_meta send_html(). 90:- public send_html/1. 91 92:- meta_predicate 93 pengine_format(,).
128:- setting(write_options, list(any), [max_depth(1000)], 129 'Additional options for stringifying Prolog results'). 130 131 132 /******************************* 133 * OUTPUT * 134 *******************************/
140pengine_writeln(Term) :- 141 pengine_output, 142 !, 143 pengine_module(Module), 144 send_html(span(class(writeln), 145 [ \term(Term, 146 [ module(Module) 147 ]), 148 br([]) 149 ])). 150pengine_writeln(Term) :- 151 writeln(Term).
157pengine_nl :- 158 pengine_output, 159 !, 160 send_html(br([])). 161pengine_nl :- 162 nl.
168pengine_tab(Expr) :- 169 pengine_output, 170 !, 171 N is Expr, 172 length(List, N), 173 maplist(=(&(nbsp)), List), 174 send_html(List). 175pengine_tab(N) :- 176 tab(N).
184pengine_flush_output :- 185 pengine_output, 186 !. 187pengine_flush_output :- 188 flush_output.
write.198pengine_write_term(Term, Options) :- 199 pengine_output, 200 !, 201 option(class(Class), Options, write), 202 pengine_module(Module), 203 send_html(span(class(Class), \term(Term,[module(Module)|Options]))). 204pengine_write_term(Term, Options) :- 205 write_term(Term, Options).
215pengine_write(Term) :- 216 pengine_write_term(Term, [numbervars(true)]). 217pengine_writeq(Term) :- 218 pengine_write_term(Term, [quoted(true), numbervars(true)]). 219pengine_display(Term) :- 220 pengine_write_term(Term, [quoted(true), ignore_ops(true)]). 221pengine_print(Term) :- 222 current_prolog_flag(print_write_options, Options), 223 pengine_write_term(Term, Options). 224pengine_write_canonical(Term) :- 225 pengine_output, 226 !, 227 with_output_to(string(String), write_canonical(Term)), 228 send_html(span(class([write, cononical]), String)). 229pengine_write_canonical(Term) :- 230 write_canonical(Term).
240pengine_format(Format) :- 241 pengine_format(Format, []). 242pengine_format(Format, Args) :- 243 pengine_output, 244 !, 245 format(string(String), Format, Args), 246 split_string(String, "\n", "", Lines), 247 send_html(\lines(Lines, format)). 248pengine_format(Format, Args) :- 249 format(Format, Args). 250 251 252 /******************************* 253 * LISTING * 254 *******************************/
262pengine_listing :- 263 pengine_listing(_). 264 265pengine_listing(Spec) :- 266 pengine_self(Module), 267 with_output_to(string(String), listing(Module:Spec)), 268 split_string(String, "", "\n", [Pre]), 269 send_html(pre(class(listing), Pre)). 270 271pengine_portray_clause(Term) :- 272 pengine_output, 273 !, 274 with_output_to(string(String), portray_clause(Term)), 275 split_string(String, "", "\n", [Pre]), 276 send_html(pre(class(listing), Pre)). 277pengine_portray_clause(Term) :- 278 portray_clause(Term). 279 280 281 /******************************* 282 * PRINT MESSAGE * 283 *******************************/ 284 285:- multifile user:message_hook/3.
292user:message_hook(Term, Kind, Lines) :-
293 Kind \== silent,
294 pengine_self(_),
295 atom_concat('msg-', Kind, Class),
296 message_lines_to_html(Lines, [Class], HTMlString),
297 ( source_location(File, Line)
298 -> Src = File:Line
299 ; Src = (-)
300 ),
301 pengine_output(message(Term, Kind, HTMlString, Src)).'prolog-message' and the given Classes.309message_lines_to_html(Lines, Classes, HTMlString) :- 310 phrase(html(pre(class(['prolog-message'|Classes]), 311 \message_lines(Lines))), Tokens), 312 with_output_to(string(HTMlString), print_html(Tokens)). 313 314message_lines([]) --> 315 !. 316message_lines([nl|T]) --> 317 !, 318 html('\n'), % we are in a <pre> environment 319 message_lines(T). 320message_lines([flush]) --> 321 !. 322message_lines([ansi(Attributes, Fmt, Args)|T]) --> 323 !, 324 { is_list(Attributes) 325 -> foldl(style, Attributes, Fmt-Args, HTML) 326 ; style(Attributes, Fmt-Args, HTML) 327 }, 328 html(HTML), 329 message_lines(T). 330message_lines([url(Pos)|T]) --> 331 !, 332 location(Pos), 333 message_lines(T). 334message_lines([url(HREF, Label)|T]) --> 335 !, 336 html(a(href(HREF),Label)), 337 message_lines(T). 338message_lines([H|T]) --> 339 html(H), 340 message_lines(T). 341 342location(File:Line:Column) --> 343 !, 344 html([File, :, Line, :, Column]). 345location(File:Line) --> 346 !, 347 html([File, :, Line]). 348location(File) --> 349 html([File]). 350 351style(bold, Content, b(Content)) :- !. 352style(fg(default), Content, span(style('color: black'), Content)) :- !. 353style(fg(Color), Content, span(style('color:'+Color), Content)) :- !. 354style(_, Content, Content). 355 356 357 /******************************* 358 * INPUT * 359 *******************************/ 360 361pengine_read(Term) :- 362 pengine_input, 363 !, 364 prompt(Prompt, Prompt), 365 pengine_input(Prompt, Term). 366pengine_read(Term) :- 367 read(Term). 368 369pengine_read_line_to_string(From, String) :- 370 pengine_input, 371 !, 372 must_be(oneof([current_input,user_input]), From), 373 ( prompt(Prompt, Prompt), 374 Prompt \== '' 375 -> true 376 ; Prompt = 'line> ' 377 ), 378 pengine_input(_{type: console, prompt:Prompt}, StringNL), 379 string_concat(String, "\n", StringNL). 380pengine_read_line_to_string(From, String) :- 381 read_line_to_string(From, String). 382 383pengine_read_line_to_codes(From, Codes) :- 384 pengine_read_line_to_string(From, String), 385 string_codes(String, Codes). 386 387 388 /******************************* 389 * HTML * 390 *******************************/ 391 392lines([], _) --> []. 393lines([H|T], Class) --> 394 html(span(class(Class), H)), 395 ( { T == [] } 396 -> [] 397 ; html(br([])), 398 lines(T, Class) 399 ).
406send_html(HTML) :-
407 phrase(html(HTML), Tokens),
408 with_output_to(string(HTMlString), print_html(Tokens)),
409 pengine_output(HTMlString).416pengine_module(Module) :- 417 pengine_self(Pengine), 418 !, 419 pengine_property(Pengine, module(Module)). 420pengine_module(user). 421 422 /******************************* 423 * OUTPUT FORMAT * 424 *******************************/
453:- multifile
454 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.)471penginesevent_to_json(success(ID, Answers0, Projection, Time, More), JSON, 472 'json-s') :- 473 !, 474 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 475 maplist(answer_to_json_strings(ID), Answers0, Answers), 476 add_projection(Projection, JSON0, JSON). 477penginesevent_to_json(output(ID, Term), JSON, 'json-s') :- 478 !, 479 map_output(ID, Term, JSON). 480 481add_projection([], JSON, JSON) :- !. 482add_projection(VarNames, JSON0, JSON0.put(projection, VarNames)).
490answer_to_json_strings(Pengine, DictIn, DictOut) :- 491 dict_pairs(DictIn, Tag, Pairs), 492 maplist(term_string_value(Pengine), Pairs, BindingsOut), 493 dict_pairs(DictOut, Tag, BindingsOut). 494 495term_string_value(Pengine, N-V, N-A) :- 496 with_output_to(string(A), 497 write_term(V, 498 [ module(Pengine), 499 quoted(true) 500 ])).
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.
514penginesevent_to_json(success(ID, Answers0, Projection, Time, More), 515 JSON, 'json-html') :- 516 !, 517 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 518 maplist(map_answer(ID), Answers0, ResVars, Answers), 519 add_projection(Projection, ResVars, JSON0, JSON). 520penginesevent_to_json(output(ID, Term), JSON, 'json-html') :- 521 !, 522 map_output(ID, Term, JSON). 523 524map_answer(ID, Bindings0, ResVars, Answer) :- 525 dict_bindings(Bindings0, Bindings1), 526 select_residuals(Bindings1, Bindings2, ResVars, Residuals0, Clauses), 527 append(Residuals0, Residuals1), 528 prolog:translate_bindings(Bindings2, Bindings3, [], Residuals1, 529 ID:Residuals-_HiddenResiduals), 530 maplist(binding_to_html(ID), Bindings3, VarBindings), 531 final_answer(ID, VarBindings, Residuals, Clauses, Answer). 532 533final_answer(_Id, VarBindings, [], [], Answer) :- 534 !, 535 Answer = json{variables:VarBindings}. 536final_answer(ID, VarBindings, Residuals, [], Answer) :- 537 !, 538 residuals_html(Residuals, ID, ResHTML), 539 Answer = json{variables:VarBindings, residuals:ResHTML}. 540final_answer(ID, VarBindings, [], Clauses, Answer) :- 541 !, 542 clauses_html(Clauses, ID, ClausesHTML), 543 Answer = json{variables:VarBindings, wfs_residual_program:ClausesHTML}. 544final_answer(ID, VarBindings, Residuals, Clauses, Answer) :- 545 !, 546 residuals_html(Residuals, ID, ResHTML), 547 clauses_html(Clauses, ID, ClausesHTML), 548 Answer = json{variables:VarBindings, 549 residuals:ResHTML, 550 wfs_residual_program:ClausesHTML}. 551 552residuals_html([], _, []). 553residuals_html([H0|T0], Module, [H|T]) :- 554 term_html_string(H0, [], Module, H, [priority(999)]), 555 residuals_html(T0, Module, T). 556 557clauses_html(Clauses, _ID, HTMLString) :- 558 with_output_to(string(Program), list_clauses(Clauses)), 559 phrase(html(pre([class('wfs-residual-program')], Program)), Tokens), 560 with_output_to(string(HTMLString), print_html(Tokens)). 561 562list_clauses([]). 563list_clauses([H|T]) :- 564 ( system_undefined(H) 565 -> true 566 ; portray_clause(H) 567 ), 568 list_clauses(T). 569 570system_undefined((undefined :- tnot(undefined))). 571system_undefined((answer_count_restraint :- tnot(answer_count_restraint))). 572system_undefined((radial_restraint :- tnot(radial_restraint))). 573 574dict_bindings(Dict, Bindings) :- 575 dict_pairs(Dict, _Tag, Pairs), 576 maplist([N-V,N=V]>>true, Pairs, Bindings). 577 578select_residuals([], [], [], [], []). 579select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 580 binding_residual(H, Var, Residual), 581 !, 582 Vars = [Var|TV], 583 Residuals = [Residual|TR], 584 select_residuals(T, Bindings, TV, TR, Clauses). 585select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 586 binding_residual_clauses(H, Var, Delays, Clauses0), 587 !, 588 Vars = [Var|TV], 589 Residuals = [Delays|TR], 590 append(Clauses0, CT, Clauses), 591 select_residuals(T, Bindings, TV, TR, CT). 592select_residuals([H|T0], [H|T], Vars, Residuals, Clauses) :- 593 select_residuals(T0, T, Vars, Residuals, Clauses). 594 595binding_residual('_residuals' = '$residuals'(Residuals), '_residuals', Residuals) :- 596 is_list(Residuals). 597binding_residual('Residuals' = '$residuals'(Residuals), 'Residuals', Residuals) :- 598 is_list(Residuals). 599binding_residual('Residual' = '$residual'(Residual), 'Residual', [Residual]) :- 600 callable(Residual). 601 602binding_residual_clauses( 603 '_wfs_residual_program' = '$wfs_residual_program'(Delays, Clauses), 604 '_wfs_residual_program', Residuals, Clauses) :- 605 phrase(delay_list(Delays), Residuals). 606 607delay_list(true) --> !. 608delay_list((A,B)) --> !, delay_list(A), delay_list(B). 609delay_list(M:A) --> !, [M:'$wfs_undefined'(A)]. 610delay_list(A) --> ['$wfs_undefined'(A)]. 611 612add_projection(-, _, JSON, JSON) :- !. 613add_projection(VarNames0, ResVars0, JSON0, JSON) :- 614 append(ResVars0, ResVars1), 615 sort(ResVars1, ResVars), 616 subtract(VarNames0, ResVars, VarNames), 617 add_projection(VarNames, JSON0, JSON).
628binding_to_html(ID, binding(Vars,Term,Substitutions), JSON) :- 629 JSON0 = json{variables:Vars, value:HTMLString}, 630 binding_write_options(ID, Options), 631 term_html_string(Term, Vars, ID, HTMLString, Options), 632 ( Substitutions == [] 633 -> JSON = JSON0 634 ; maplist(subst_to_html(ID), Substitutions, HTMLSubst), 635 JSON = JSON0.put(substitutions, HTMLSubst) 636 ). 637 638binding_write_options(Pengine, Options) :- 639 ( current_predicate(Pengine:screen_property/1), 640 Pengine:screen_property(tabled(true)) 641 -> Options = [] 642 ; Options = [priority(699)] 643 ).
652term_html_string(Term, Vars, Module, HTMLString, Options) :-
653 setting(write_options, WOptions),
654 merge_options(WOptions,
655 [ quoted(true),
656 numbervars(true),
657 module(Module)
658 | Options
659 ], WriteOptions),
660 phrase(term_html(Term, Vars, WriteOptions), Tokens),
661 with_output_to(string(HTMLString), print_html(Tokens)).673:- multifile binding_term//3. 674 675term_html(Term, Vars, WriteOptions) --> 676 { nonvar(Term) }, 677 binding_term(Term, Vars, WriteOptions), 678 !. 679term_html(Undef, _Vars, WriteOptions) --> 680 { nonvar(Undef), 681 Undef = '$wfs_undefined'(Term), 682 ! 683 }, 684 html(span(class(wfs_undefined), \term(Term, WriteOptions))). 685term_html(Term, _Vars, WriteOptions) --> 686 term(Term, WriteOptions).
693subst_to_html(ID, '$VAR'(Name)=Value, json{var:Name, value:HTMLString}) :- 694 !, 695 binding_write_options(ID, Options), 696 term_html_string(Value, [Name], ID, HTMLString, Options). 697subst_to_html(_, Term, _) :- 698 assertion(Term = '$VAR'(_)).
705map_output(ID, message(Term, Kind, HTMLString, Src), JSON) :- 706 atomic(HTMLString), 707 !, 708 JSON0 = json{event:output, id:ID, message:Kind, data:HTMLString}, 709 pengines:add_error_details(Term, JSON0, JSON1), 710 ( Src = File:Line, 711 \+ JSON1.get(location) = _ 712 -> JSON = JSON1.put(_{location:_{file:File, line:Line}}) 713 ; JSON = JSON1 714 ). 715map_output(ID, Term, json{event:output, id:ID, data:Data}) :- 716 ( atomic(Term) 717 -> Data = Term 718 ; is_dict(Term, json), 719 ground(json) % TBD: Check proper JSON object? 720 -> Data = Term 721 ; term_string(Term, Data) 722 ).
729:- multifile 730 prolog_help:show_html_hook/1. 731 732prolog_helpshow_html_hook(HTML) :- 733 pengine_output, 734 pengine_output(HTML). 735 736 737 /******************************* 738 * SANDBOXING * 739 *******************************/ 740 741:- multifile 742 sandbox:safe_primitive/1, % Goal 743 sandbox:safe_meta/2. % Goal, Called 744 745sandbox:safe_primitive(pengines_io:pengine_listing(_)). 746sandbox:safe_primitive(pengines_io:pengine_nl). 747sandbox:safe_primitive(pengines_io:pengine_tab(_)). 748sandbox:safe_primitive(pengines_io:pengine_flush_output). 749sandbox:safe_primitive(pengines_io:pengine_print(_)). 750sandbox:safe_primitive(pengines_io:pengine_write(_)). 751sandbox:safe_primitive(pengines_io:pengine_read(_)). 752sandbox:safe_primitive(pengines_io:pengine_read_line_to_string(_,_)). 753sandbox:safe_primitive(pengines_io:pengine_read_line_to_codes(_,_)). 754sandbox:safe_primitive(pengines_io:pengine_write_canonical(_)). 755sandbox:safe_primitive(pengines_io:pengine_write_term(_,_)). 756sandbox:safe_primitive(pengines_io:pengine_writeln(_)). 757sandbox:safe_primitive(pengines_io:pengine_writeq(_)). 758sandbox:safe_primitive(pengines_io:pengine_portray_clause(_)). 759sandbox:safe_primitive(system:write_term(_,_)). 760sandbox:safe_primitive(system:prompt(_,_)). 761sandbox:safe_primitive(system:statistics(_,_)). 762 763sandbox:safe_meta(pengines_io:pengine_format(Format, Args), Calls) :- 764 sandbox:format_calls(Format, Args, Calls). 765 766 767 /******************************* 768 * REDEFINITION * 769 *******************************/
776pengine_io_predicate(writeln(_)). 777pengine_io_predicate(nl). 778pengine_io_predicate(tab(_)). 779pengine_io_predicate(flush_output). 780pengine_io_predicate(format(_)). 781pengine_io_predicate(format(_,_)). 782pengine_io_predicate(read(_)). 783pengine_io_predicate(read_line_to_string(_,_)). 784pengine_io_predicate(read_line_to_codes(_,_)). 785pengine_io_predicate(write_term(_,_)). 786pengine_io_predicate(write(_)). 787pengine_io_predicate(writeq(_)). 788pengine_io_predicate(display(_)). 789pengine_io_predicate(print(_)). 790pengine_io_predicate(write_canonical(_)). 791pengine_io_predicate(listing). 792pengine_io_predicate(listing(_)). 793pengine_io_predicate(portray_clause(_)). 794 795term_expansion(pengine_io_goal_expansion(_,_), 796 Clauses) :- 797 findall(Clause, io_mapping(Clause), Clauses). 798 799io_mapping(pengine_io_goal_expansion(Head, Mapped)) :- 800 pengine_io_predicate(Head), 801 Head =.. [Name|Args], 802 atom_concat(pengine_, Name, BodyName), 803 Mapped =.. [BodyName|Args]. 804 805pengine_io_goal_expansion(_, _). 806 807 808 /******************************* 809 * REBIND PENGINE I/O * 810 *******************************/ 811 812:- public 813 stream_write/2, 814 stream_read/2, 815 stream_close/1. 816 817:- thread_local 818 pengine_io/2. 819 820stream_write(Stream, Out) :- 821 ( pengine_io(_,_) 822 -> send_html(pre(class(console), Out)) 823 ; current_prolog_flag(pengine_main_thread, TID), 824 thread_signal(TID, stream_write(Stream, Out)) 825 ). 826stream_read(Stream, Data) :- 827 ( pengine_io(_,_) 828 -> prompt(Prompt, Prompt), 829 pengine_input(_{type:console, prompt:Prompt}, Data) 830 ; current_prolog_flag(pengine_main_thread, TID), 831 call_in_thread(TID, stream_read(Stream, Data)) 832 ). 833stream_close(_Stream).
843pengine_bind_user_streams :- 844 Err = Out, 845 open_prolog_stream(pengines_io, write, Out, []), 846 set_stream(Out, buffer(line)), 847 open_prolog_stream(pengines_io, read, In, []), 848 set_stream(In, alias(user_input)), 849 set_stream(Out, alias(user_output)), 850 set_stream(Err, alias(user_error)), 851 set_stream(In, alias(current_input)), 852 set_stream(Out, alias(current_output)), 853 assertz(pengine_io(In, Out)), 854 thread_self(Me), 855 thread_property(Me, id(Id)), 856 set_prolog_flag(pengine_main_thread, Id), 857 thread_at_exit(close_io). 858 859close_io :- 860 retract(pengine_io(In, Out)), 861 !, 862 close(In, [force(true)]), 863 close(Out, [force(true)]). 864close_io.
871pengine_output :- 872 current_output(Out), 873 pengine_io(_, Out). 874 875pengine_input :- 876 current_input(In), 877 pengine_io(In, _).
885pengine_bind_io_to_html(Module) :- 886 forall(pengine_io_predicate(Head), 887 bind_io(Head, Module)), 888 pengine_bind_user_streams. 889 890bind_io(Head, Module) :- 891 prompt(_, ''), 892 redefine_system_predicate(Module:Head), 893 functor(Head, Name, Arity), 894 Head =.. [Name|Args], 895 atom_concat(pengine_, Name, BodyName), 896 Body =.. [BodyName|Args], 897 assertz(Module:(Head :- Body)), 898 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).*/