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_flush_output/0, 40 pengine_format/1, % +Format 41 pengine_format/2, % +Format, +Args 42 43 pengine_write_term/2, % +Term, +Options 44 pengine_write/1, % +Term 45 pengine_writeq/1, % +Term 46 pengine_display/1, % +Term 47 pengine_print/1, % +Term 48 pengine_write_canonical/1, % +Term 49 50 pengine_listing/0, 51 pengine_listing/1, % +Spec 52 pengine_portray_clause/1, % +Term 53 54 pengine_read/1, % -Term 55 pengine_read_line_to_string/2, % +Stream, -LineAsString 56 pengine_read_line_to_codes/2, % +Stream, -LineAsCodes 57 58 pengine_io_predicate/1, % ?Head 59 pengine_bind_io_to_html/1, % +Module 60 pengine_io_goal_expansion/2,% +Goal, -Expanded 61 62 message_lines_to_html/3 % +Lines, +Classes, -HTML 63 ]). 64:- autoload(library(apply),[foldl/4,maplist/3,maplist/4]). 65:- autoload(library(backcomp),[thread_at_exit/1]). 66:- autoload(library(debug),[assertion/1]). 67:- autoload(library(error),[must_be/2]). 68:- autoload(library(listing),[listing/1,portray_clause/1]). 69:- autoload(library(lists),[append/2,append/3,subtract/3]). 70:- autoload(library(option),[option/3,merge_options/3]). 71:- autoload(library(pengines), 72 [ pengine_self/1, 73 pengine_output/1, 74 pengine_input/2, 75 pengine_property/2 76 ]). 77:- autoload(library(prolog_stream),[open_prolog_stream/4]). 78:- autoload(library(readutil),[read_line_to_string/2]). 79:- autoload(library(yall),[(>>)/4]). 80:- autoload(library(http/term_html),[term/4]). 81 82:- use_module(library(http/html_write),[html/3,print_html/1, op(_,_,_)]). 83:- use_module(library(settings),[setting/4,setting/2]). 84 85:- use_module(library(sandbox), []). 86:- autoload(library(thread), [call_in_thread/2]). 87 88:- html_meta send_html(). 89:- public send_html/1. 90 91:- meta_predicate 92 pengine_format(,).
127:- setting(write_options, list(any), [max_depth(1000)], 128 'Additional options for stringifying Prolog results'). 129 130 131 /******************************* 132 * OUTPUT * 133 *******************************/
139pengine_writeln(Term) :- 140 pengine_output, 141 !, 142 pengine_module(Module), 143 send_html(span(class(writeln), 144 [ \term(Term, 145 [ module(Module) 146 ]), 147 br([]) 148 ])). 149pengine_writeln(Term) :- 150 writeln(Term).
156pengine_nl :- 157 pengine_output, 158 !, 159 send_html(br([])). 160pengine_nl :- 161 nl.
168pengine_flush_output :- 169 pengine_output, 170 !. 171pengine_flush_output :- 172 flush_output.
write.182pengine_write_term(Term, Options) :- 183 pengine_output, 184 !, 185 option(class(Class), Options, write), 186 pengine_module(Module), 187 send_html(span(class(Class), \term(Term,[module(Module)|Options]))). 188pengine_write_term(Term, Options) :- 189 write_term(Term, Options).
199pengine_write(Term) :- 200 pengine_write_term(Term, [numbervars(true)]). 201pengine_writeq(Term) :- 202 pengine_write_term(Term, [quoted(true), numbervars(true)]). 203pengine_display(Term) :- 204 pengine_write_term(Term, [quoted(true), ignore_ops(true)]). 205pengine_print(Term) :- 206 current_prolog_flag(print_write_options, Options), 207 pengine_write_term(Term, Options). 208pengine_write_canonical(Term) :- 209 pengine_output, 210 !, 211 with_output_to(string(String), write_canonical(Term)), 212 send_html(span(class([write, cononical]), String)). 213pengine_write_canonical(Term) :- 214 write_canonical(Term).
224pengine_format(Format) :- 225 pengine_format(Format, []). 226pengine_format(Format, Args) :- 227 pengine_output, 228 !, 229 format(string(String), Format, Args), 230 split_string(String, "\n", "", Lines), 231 send_html(\lines(Lines, format)). 232pengine_format(Format, Args) :- 233 format(Format, Args). 234 235 236 /******************************* 237 * LISTING * 238 *******************************/
246pengine_listing :- 247 pengine_listing(_). 248 249pengine_listing(Spec) :- 250 pengine_self(Module), 251 with_output_to(string(String), listing(Module:Spec)), 252 split_string(String, "", "\n", [Pre]), 253 send_html(pre(class(listing), Pre)). 254 255pengine_portray_clause(Term) :- 256 pengine_output, 257 !, 258 with_output_to(string(String), portray_clause(Term)), 259 split_string(String, "", "\n", [Pre]), 260 send_html(pre(class(listing), Pre)). 261pengine_portray_clause(Term) :- 262 portray_clause(Term). 263 264 265 /******************************* 266 * PRINT MESSAGE * 267 *******************************/ 268 269:- multifile user:message_hook/3.
276user:message_hook(Term, Kind, Lines) :-
277 Kind \== silent,
278 pengine_self(_),
279 atom_concat('msg-', Kind, Class),
280 message_lines_to_html(Lines, [Class], HTMlString),
281 ( source_location(File, Line)
282 -> Src = File:Line
283 ; Src = (-)
284 ),
285 pengine_output(message(Term, Kind, HTMlString, Src)).'prolog-message' and the given Classes.293message_lines_to_html(Lines, Classes, HTMlString) :- 294 phrase(html(pre(class(['prolog-message'|Classes]), 295 \message_lines(Lines))), Tokens), 296 with_output_to(string(HTMlString), print_html(Tokens)). 297 298message_lines([]) --> 299 !. 300message_lines([nl|T]) --> 301 !, 302 html('\n'), % we are in a <pre> environment 303 message_lines(T). 304message_lines([flush]) --> 305 !. 306message_lines([ansi(Attributes, Fmt, Args)|T]) --> 307 !, 308 { is_list(Attributes) 309 -> foldl(style, Attributes, Fmt-Args, HTML) 310 ; style(Attributes, Fmt-Args, HTML) 311 }, 312 html(HTML), 313 message_lines(T). 314message_lines([H|T]) --> 315 html(H), 316 message_lines(T). 317 318style(bold, Content, b(Content)) :- !. 319style(fg(default), Content, span(style('color: black'), Content)) :- !. 320style(fg(Color), Content, span(style('color:'+Color), Content)) :- !. 321style(_, Content, Content). 322 323 324 /******************************* 325 * INPUT * 326 *******************************/ 327 328pengine_read(Term) :- 329 pengine_input, 330 !, 331 prompt(Prompt, Prompt), 332 pengine_input(Prompt, Term). 333pengine_read(Term) :- 334 read(Term). 335 336pengine_read_line_to_string(From, String) :- 337 pengine_input, 338 !, 339 must_be(oneof([current_input,user_input]), From), 340 ( prompt(Prompt, Prompt), 341 Prompt \== '' 342 -> true 343 ; Prompt = 'line> ' 344 ), 345 pengine_input(_{type: console, prompt:Prompt}, StringNL), 346 string_concat(String, "\n", StringNL). 347pengine_read_line_to_string(From, String) :- 348 read_line_to_string(From, String). 349 350pengine_read_line_to_codes(From, Codes) :- 351 pengine_read_line_to_string(From, String), 352 string_codes(String, Codes). 353 354 355 /******************************* 356 * HTML * 357 *******************************/ 358 359lines([], _) --> []. 360lines([H|T], Class) --> 361 html(span(class(Class), H)), 362 ( { T == [] } 363 -> [] 364 ; html(br([])), 365 lines(T, Class) 366 ).
373send_html(HTML) :-
374 phrase(html(HTML), Tokens),
375 with_output_to(string(HTMlString), print_html(Tokens)),
376 pengine_output(HTMlString).383pengine_module(Module) :- 384 pengine_self(Pengine), 385 !, 386 pengine_property(Pengine, module(Module)). 387pengine_module(user). 388 389 /******************************* 390 * OUTPUT FORMAT * 391 *******************************/
420:- multifile
421 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.)438penginesevent_to_json(success(ID, Answers0, Projection, Time, More), JSON, 439 'json-s') :- 440 !, 441 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 442 maplist(answer_to_json_strings(ID), Answers0, Answers), 443 add_projection(Projection, JSON0, JSON). 444penginesevent_to_json(output(ID, Term), JSON, 'json-s') :- 445 !, 446 map_output(ID, Term, JSON). 447 448add_projection([], JSON, JSON) :- !. 449add_projection(VarNames, JSON0, JSON0.put(projection, VarNames)).
457answer_to_json_strings(Pengine, DictIn, DictOut) :- 458 dict_pairs(DictIn, Tag, Pairs), 459 maplist(term_string_value(Pengine), Pairs, BindingsOut), 460 dict_pairs(DictOut, Tag, BindingsOut). 461 462term_string_value(Pengine, N-V, N-A) :- 463 with_output_to(string(A), 464 write_term(V, 465 [ module(Pengine), 466 quoted(true) 467 ])).
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.
481penginesevent_to_json(success(ID, Answers0, Projection, Time, More), 482 JSON, 'json-html') :- 483 !, 484 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 485 maplist(map_answer(ID), Answers0, ResVars, Answers), 486 add_projection(Projection, ResVars, JSON0, JSON). 487penginesevent_to_json(output(ID, Term), JSON, 'json-html') :- 488 !, 489 map_output(ID, Term, JSON). 490 491map_answer(ID, Bindings0, ResVars, Answer) :- 492 dict_bindings(Bindings0, Bindings1), 493 select_residuals(Bindings1, Bindings2, ResVars, Residuals0, Clauses), 494 append(Residuals0, Residuals1), 495 prolog:translate_bindings(Bindings2, Bindings3, [], Residuals1, 496 ID:Residuals-_HiddenResiduals), 497 maplist(binding_to_html(ID), Bindings3, VarBindings), 498 final_answer(ID, VarBindings, Residuals, Clauses, Answer). 499 500final_answer(_Id, VarBindings, [], [], Answer) :- 501 !, 502 Answer = json{variables:VarBindings}. 503final_answer(ID, VarBindings, Residuals, [], Answer) :- 504 !, 505 residuals_html(Residuals, ID, ResHTML), 506 Answer = json{variables:VarBindings, residuals:ResHTML}. 507final_answer(ID, VarBindings, [], Clauses, Answer) :- 508 !, 509 clauses_html(Clauses, ID, ClausesHTML), 510 Answer = json{variables:VarBindings, wfs_residual_program:ClausesHTML}. 511final_answer(ID, VarBindings, Residuals, Clauses, Answer) :- 512 !, 513 residuals_html(Residuals, ID, ResHTML), 514 clauses_html(Clauses, ID, ClausesHTML), 515 Answer = json{variables:VarBindings, 516 residuals:ResHTML, 517 wfs_residual_program:ClausesHTML}. 518 519residuals_html([], _, []). 520residuals_html([H0|T0], Module, [H|T]) :- 521 term_html_string(H0, [], Module, H, [priority(999)]), 522 residuals_html(T0, Module, T). 523 524clauses_html(Clauses, _ID, HTMLString) :- 525 with_output_to(string(Program), list_clauses(Clauses)), 526 phrase(html(pre([class('wfs-residual-program')], Program)), Tokens), 527 with_output_to(string(HTMLString), print_html(Tokens)). 528 529list_clauses([]). 530list_clauses([H|T]) :- 531 ( system_undefined(H) 532 -> true 533 ; portray_clause(H) 534 ), 535 list_clauses(T). 536 537system_undefined((undefined :- tnot(undefined))). 538system_undefined((answer_count_restraint :- tnot(answer_count_restraint))). 539system_undefined((radial_restraint :- tnot(radial_restraint))). 540 541dict_bindings(Dict, Bindings) :- 542 dict_pairs(Dict, _Tag, Pairs), 543 maplist([N-V,N=V]>>true, Pairs, Bindings). 544 545select_residuals([], [], [], [], []). 546select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 547 binding_residual(H, Var, Residual), 548 !, 549 Vars = [Var|TV], 550 Residuals = [Residual|TR], 551 select_residuals(T, Bindings, TV, TR, Clauses). 552select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 553 binding_residual_clauses(H, Var, Delays, Clauses0), 554 !, 555 Vars = [Var|TV], 556 Residuals = [Delays|TR], 557 append(Clauses0, CT, Clauses), 558 select_residuals(T, Bindings, TV, TR, CT). 559select_residuals([H|T0], [H|T], Vars, Residuals, Clauses) :- 560 select_residuals(T0, T, Vars, Residuals, Clauses). 561 562binding_residual('_residuals' = '$residuals'(Residuals), '_residuals', Residuals) :- 563 is_list(Residuals). 564binding_residual('Residuals' = '$residuals'(Residuals), 'Residuals', Residuals) :- 565 is_list(Residuals). 566binding_residual('Residual' = '$residual'(Residual), 'Residual', [Residual]) :- 567 callable(Residual). 568 569binding_residual_clauses( 570 '_wfs_residual_program' = '$wfs_residual_program'(Delays, Clauses), 571 '_wfs_residual_program', Residuals, Clauses) :- 572 phrase(comma_list(Delays), Residuals). 573 574comma_list(true) --> !. 575comma_list((A,B)) --> !, comma_list(A), comma_list(B). 576comma_list(A) --> [A]. 577 578add_projection(-, _, JSON, JSON) :- !. 579add_projection(VarNames0, ResVars0, JSON0, JSON) :- 580 append(ResVars0, ResVars1), 581 sort(ResVars1, ResVars), 582 subtract(VarNames0, ResVars, VarNames), 583 add_projection(VarNames, JSON0, JSON).
594binding_to_html(ID, binding(Vars,Term,Substitutions), JSON) :- 595 JSON0 = json{variables:Vars, value:HTMLString}, 596 binding_write_options(ID, Options), 597 term_html_string(Term, Vars, ID, HTMLString, Options), 598 ( Substitutions == [] 599 -> JSON = JSON0 600 ; maplist(subst_to_html(ID), Substitutions, HTMLSubst), 601 JSON = JSON0.put(substitutions, HTMLSubst) 602 ). 603 604binding_write_options(Pengine, Options) :- 605 ( current_predicate(Pengine:screen_property/1), 606 Pengine:screen_property(tabled(true)) 607 -> Options = [] 608 ; Options = [priority(699)] 609 ).
618term_html_string(Term, Vars, Module, HTMLString, Options) :-
619 setting(write_options, WOptions),
620 merge_options(WOptions,
621 [ quoted(true),
622 numbervars(true),
623 module(Module)
624 | Options
625 ], WriteOptions),
626 phrase(term_html(Term, Vars, WriteOptions), Tokens),
627 with_output_to(string(HTMLString), print_html(Tokens)).639:- multifile binding_term//3. 640 641term_html(Term, Vars, WriteOptions) --> 642 { nonvar(Term) }, 643 binding_term(Term, Vars, WriteOptions), 644 !. 645term_html(Term, _Vars, WriteOptions) --> 646 term(Term, WriteOptions).
653subst_to_html(ID, '$VAR'(Name)=Value, json{var:Name, value:HTMLString}) :- 654 !, 655 binding_write_options(ID, Options), 656 term_html_string(Value, [Name], ID, HTMLString, Options). 657subst_to_html(_, Term, _) :- 658 assertion(Term = '$VAR'(_)).
665map_output(ID, message(Term, Kind, HTMLString, Src), JSON) :- 666 atomic(HTMLString), 667 !, 668 JSON0 = json{event:output, id:ID, message:Kind, data:HTMLString}, 669 pengines:add_error_details(Term, JSON0, JSON1), 670 ( Src = File:Line, 671 \+ JSON1.get(location) = _ 672 -> JSON = JSON1.put(_{location:_{file:File, line:Line}}) 673 ; JSON = JSON1 674 ). 675map_output(ID, Term, json{event:output, id:ID, data:Data}) :- 676 ( atomic(Term) 677 -> Data = Term 678 ; is_dict(Term, json), 679 ground(json) % TBD: Check proper JSON object? 680 -> Data = Term 681 ; term_string(Term, Data) 682 ).
689:- multifile 690 prolog_help:show_html_hook/1. 691 692prolog_helpshow_html_hook(HTML) :- 693 pengine_output, 694 pengine_output(HTML). 695 696 697 /******************************* 698 * SANDBOXING * 699 *******************************/ 700 701:- multifile 702 sandbox:safe_primitive/1, % Goal 703 sandbox:safe_meta/2. % Goal, Called 704 705sandbox:safe_primitive(pengines_io:pengine_listing(_)). 706sandbox:safe_primitive(pengines_io:pengine_nl). 707sandbox:safe_primitive(pengines_io:pengine_flush_output). 708sandbox:safe_primitive(pengines_io:pengine_print(_)). 709sandbox:safe_primitive(pengines_io:pengine_write(_)). 710sandbox:safe_primitive(pengines_io:pengine_read(_)). 711sandbox:safe_primitive(pengines_io:pengine_read_line_to_string(_,_)). 712sandbox:safe_primitive(pengines_io:pengine_read_line_to_codes(_,_)). 713sandbox:safe_primitive(pengines_io:pengine_write_canonical(_)). 714sandbox:safe_primitive(pengines_io:pengine_write_term(_,_)). 715sandbox:safe_primitive(pengines_io:pengine_writeln(_)). 716sandbox:safe_primitive(pengines_io:pengine_writeq(_)). 717sandbox:safe_primitive(pengines_io:pengine_portray_clause(_)). 718sandbox:safe_primitive(system:write_term(_,_)). 719sandbox:safe_primitive(system:prompt(_,_)). 720sandbox:safe_primitive(system:statistics(_,_)). 721 722sandbox:safe_meta(pengines_io:pengine_format(Format, Args), Calls) :- 723 sandbox:format_calls(Format, Args, Calls). 724 725 726 /******************************* 727 * REDEFINITION * 728 *******************************/
735pengine_io_predicate(writeln(_)). 736pengine_io_predicate(nl). 737pengine_io_predicate(flush_output). 738pengine_io_predicate(format(_)). 739pengine_io_predicate(format(_,_)). 740pengine_io_predicate(read(_)). 741pengine_io_predicate(read_line_to_string(_,_)). 742pengine_io_predicate(read_line_to_codes(_,_)). 743pengine_io_predicate(write_term(_,_)). 744pengine_io_predicate(write(_)). 745pengine_io_predicate(writeq(_)). 746pengine_io_predicate(display(_)). 747pengine_io_predicate(print(_)). 748pengine_io_predicate(write_canonical(_)). 749pengine_io_predicate(listing). 750pengine_io_predicate(listing(_)). 751pengine_io_predicate(portray_clause(_)). 752 753term_expansion(pengine_io_goal_expansion(_,_), 754 Clauses) :- 755 findall(Clause, io_mapping(Clause), Clauses). 756 757io_mapping(pengine_io_goal_expansion(Head, Mapped)) :- 758 pengine_io_predicate(Head), 759 Head =.. [Name|Args], 760 atom_concat(pengine_, Name, BodyName), 761 Mapped =.. [BodyName|Args]. 762 763pengine_io_goal_expansion(_, _). 764 765 766 /******************************* 767 * REBIND PENGINE I/O * 768 *******************************/ 769 770:- public 771 stream_write/2, 772 stream_read/2, 773 stream_close/1. 774 775:- thread_local 776 pengine_io/2. 777 778stream_write(Stream, Out) :- 779 ( pengine_io(_,_) 780 -> send_html(pre(class(console), Out)) 781 ; current_prolog_flag(pengine_main_thread, TID), 782 thread_signal(TID, stream_write(Stream, Out)) 783 ). 784stream_read(Stream, Data) :- 785 ( pengine_io(_,_) 786 -> prompt(Prompt, Prompt), 787 pengine_input(_{type:console, prompt:Prompt}, Data) 788 ; current_prolog_flag(pengine_main_thread, TID), 789 call_in_thread(TID, stream_read(Stream, Data)) 790 ). 791stream_close(_Stream).
801pengine_bind_user_streams :- 802 Err = Out, 803 open_prolog_stream(pengines_io, write, Out, []), 804 set_stream(Out, buffer(line)), 805 open_prolog_stream(pengines_io, read, In, []), 806 set_stream(In, alias(user_input)), 807 set_stream(Out, alias(user_output)), 808 set_stream(Err, alias(user_error)), 809 set_stream(In, alias(current_input)), 810 set_stream(Out, alias(current_output)), 811 assertz(pengine_io(In, Out)), 812 thread_self(Me), 813 thread_property(Me, id(Id)), 814 set_prolog_flag(pengine_main_thread, Id), 815 thread_at_exit(close_io). 816 817close_io :- 818 retract(pengine_io(In, Out)), 819 !, 820 close(In, [force(true)]), 821 close(Out, [force(true)]). 822close_io.
829pengine_output :- 830 current_output(Out), 831 pengine_io(_, Out). 832 833pengine_input :- 834 current_input(In), 835 pengine_io(In, _).
843pengine_bind_io_to_html(Module) :- 844 forall(pengine_io_predicate(Head), 845 bind_io(Head, Module)), 846 pengine_bind_user_streams. 847 848bind_io(Head, Module) :- 849 prompt(_, ''), 850 redefine_system_predicate(Module:Head), 851 functor(Head, Name, Arity), 852 Head =.. [Name|Args], 853 atom_concat(pengine_, Name, BodyName), 854 Body =.. [BodyName|Args], 855 assertz(Module:(Head :- Body)), 856 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).*/