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(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(N) :- 169 pengine_output, 170 !, 171 length(List, N), 172 maplist(=(&(nbsp)), List), 173 send_html(List). 174pengine_tab(N) :- 175 tab(N).
183pengine_flush_output :- 184 pengine_output, 185 !. 186pengine_flush_output :- 187 flush_output.
write.197pengine_write_term(Term, Options) :- 198 pengine_output, 199 !, 200 option(class(Class), Options, write), 201 pengine_module(Module), 202 send_html(span(class(Class), \term(Term,[module(Module)|Options]))). 203pengine_write_term(Term, Options) :- 204 write_term(Term, Options).
214pengine_write(Term) :- 215 pengine_write_term(Term, [numbervars(true)]). 216pengine_writeq(Term) :- 217 pengine_write_term(Term, [quoted(true), numbervars(true)]). 218pengine_display(Term) :- 219 pengine_write_term(Term, [quoted(true), ignore_ops(true)]). 220pengine_print(Term) :- 221 current_prolog_flag(print_write_options, Options), 222 pengine_write_term(Term, Options). 223pengine_write_canonical(Term) :- 224 pengine_output, 225 !, 226 with_output_to(string(String), write_canonical(Term)), 227 send_html(span(class([write, cononical]), String)). 228pengine_write_canonical(Term) :- 229 write_canonical(Term).
239pengine_format(Format) :- 240 pengine_format(Format, []). 241pengine_format(Format, Args) :- 242 pengine_output, 243 !, 244 format(string(String), Format, Args), 245 split_string(String, "\n", "", Lines), 246 send_html(\lines(Lines, format)). 247pengine_format(Format, Args) :- 248 format(Format, Args). 249 250 251 /******************************* 252 * LISTING * 253 *******************************/
261pengine_listing :- 262 pengine_listing(_). 263 264pengine_listing(Spec) :- 265 pengine_self(Module), 266 with_output_to(string(String), listing(Module:Spec)), 267 split_string(String, "", "\n", [Pre]), 268 send_html(pre(class(listing), Pre)). 269 270pengine_portray_clause(Term) :- 271 pengine_output, 272 !, 273 with_output_to(string(String), portray_clause(Term)), 274 split_string(String, "", "\n", [Pre]), 275 send_html(pre(class(listing), Pre)). 276pengine_portray_clause(Term) :- 277 portray_clause(Term). 278 279 280 /******************************* 281 * PRINT MESSAGE * 282 *******************************/ 283 284:- multifile user:message_hook/3.
291user:message_hook(Term, Kind, Lines) :-
292 Kind \== silent,
293 pengine_self(_),
294 atom_concat('msg-', Kind, Class),
295 message_lines_to_html(Lines, [Class], HTMlString),
296 ( source_location(File, Line)
297 -> Src = File:Line
298 ; Src = (-)
299 ),
300 pengine_output(message(Term, Kind, HTMlString, Src)).'prolog-message' and the given Classes.308message_lines_to_html(Lines, Classes, HTMlString) :- 309 phrase(html(pre(class(['prolog-message'|Classes]), 310 \message_lines(Lines))), Tokens), 311 with_output_to(string(HTMlString), print_html(Tokens)). 312 313message_lines([]) --> 314 !. 315message_lines([nl|T]) --> 316 !, 317 html('\n'), % we are in a <pre> environment 318 message_lines(T). 319message_lines([flush]) --> 320 !. 321message_lines([ansi(Attributes, Fmt, Args)|T]) --> 322 !, 323 { is_list(Attributes) 324 -> foldl(style, Attributes, Fmt-Args, HTML) 325 ; style(Attributes, Fmt-Args, HTML) 326 }, 327 html(HTML), 328 message_lines(T). 329message_lines([H|T]) --> 330 html(H), 331 message_lines(T). 332 333style(bold, Content, b(Content)) :- !. 334style(fg(default), Content, span(style('color: black'), Content)) :- !. 335style(fg(Color), Content, span(style('color:'+Color), Content)) :- !. 336style(_, Content, Content). 337 338 339 /******************************* 340 * INPUT * 341 *******************************/ 342 343pengine_read(Term) :- 344 pengine_input, 345 !, 346 prompt(Prompt, Prompt), 347 pengine_input(Prompt, Term). 348pengine_read(Term) :- 349 read(Term). 350 351pengine_read_line_to_string(From, String) :- 352 pengine_input, 353 !, 354 must_be(oneof([current_input,user_input]), From), 355 ( prompt(Prompt, Prompt), 356 Prompt \== '' 357 -> true 358 ; Prompt = 'line> ' 359 ), 360 pengine_input(_{type: console, prompt:Prompt}, StringNL), 361 string_concat(String, "\n", StringNL). 362pengine_read_line_to_string(From, String) :- 363 read_line_to_string(From, String). 364 365pengine_read_line_to_codes(From, Codes) :- 366 pengine_read_line_to_string(From, String), 367 string_codes(String, Codes). 368 369 370 /******************************* 371 * HTML * 372 *******************************/ 373 374lines([], _) --> []. 375lines([H|T], Class) --> 376 html(span(class(Class), H)), 377 ( { T == [] } 378 -> [] 379 ; html(br([])), 380 lines(T, Class) 381 ).
388send_html(HTML) :-
389 phrase(html(HTML), Tokens),
390 with_output_to(string(HTMlString), print_html(Tokens)),
391 pengine_output(HTMlString).398pengine_module(Module) :- 399 pengine_self(Pengine), 400 !, 401 pengine_property(Pengine, module(Module)). 402pengine_module(user). 403 404 /******************************* 405 * OUTPUT FORMAT * 406 *******************************/
435:- multifile
436 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.)453penginesevent_to_json(success(ID, Answers0, Projection, Time, More), JSON, 454 'json-s') :- 455 !, 456 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 457 maplist(answer_to_json_strings(ID), Answers0, Answers), 458 add_projection(Projection, JSON0, JSON). 459penginesevent_to_json(output(ID, Term), JSON, 'json-s') :- 460 !, 461 map_output(ID, Term, JSON). 462 463add_projection([], JSON, JSON) :- !. 464add_projection(VarNames, JSON0, JSON0.put(projection, VarNames)).
472answer_to_json_strings(Pengine, DictIn, DictOut) :- 473 dict_pairs(DictIn, Tag, Pairs), 474 maplist(term_string_value(Pengine), Pairs, BindingsOut), 475 dict_pairs(DictOut, Tag, BindingsOut). 476 477term_string_value(Pengine, N-V, N-A) :- 478 with_output_to(string(A), 479 write_term(V, 480 [ module(Pengine), 481 quoted(true) 482 ])).
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.
496penginesevent_to_json(success(ID, Answers0, Projection, Time, More), 497 JSON, 'json-html') :- 498 !, 499 JSON0 = json{event:success, id:ID, time:Time, data:Answers, more:More}, 500 maplist(map_answer(ID), Answers0, ResVars, Answers), 501 add_projection(Projection, ResVars, JSON0, JSON). 502penginesevent_to_json(output(ID, Term), JSON, 'json-html') :- 503 !, 504 map_output(ID, Term, JSON). 505 506map_answer(ID, Bindings0, ResVars, Answer) :- 507 dict_bindings(Bindings0, Bindings1), 508 select_residuals(Bindings1, Bindings2, ResVars, Residuals0, Clauses), 509 append(Residuals0, Residuals1), 510 prolog:translate_bindings(Bindings2, Bindings3, [], Residuals1, 511 ID:Residuals-_HiddenResiduals), 512 maplist(binding_to_html(ID), Bindings3, VarBindings), 513 final_answer(ID, VarBindings, Residuals, Clauses, Answer). 514 515final_answer(_Id, VarBindings, [], [], Answer) :- 516 !, 517 Answer = json{variables:VarBindings}. 518final_answer(ID, VarBindings, Residuals, [], Answer) :- 519 !, 520 residuals_html(Residuals, ID, ResHTML), 521 Answer = json{variables:VarBindings, residuals:ResHTML}. 522final_answer(ID, VarBindings, [], Clauses, Answer) :- 523 !, 524 clauses_html(Clauses, ID, ClausesHTML), 525 Answer = json{variables:VarBindings, wfs_residual_program:ClausesHTML}. 526final_answer(ID, VarBindings, Residuals, Clauses, Answer) :- 527 !, 528 residuals_html(Residuals, ID, ResHTML), 529 clauses_html(Clauses, ID, ClausesHTML), 530 Answer = json{variables:VarBindings, 531 residuals:ResHTML, 532 wfs_residual_program:ClausesHTML}. 533 534residuals_html([], _, []). 535residuals_html([H0|T0], Module, [H|T]) :- 536 term_html_string(H0, [], Module, H, [priority(999)]), 537 residuals_html(T0, Module, T). 538 539clauses_html(Clauses, _ID, HTMLString) :- 540 with_output_to(string(Program), list_clauses(Clauses)), 541 phrase(html(pre([class('wfs-residual-program')], Program)), Tokens), 542 with_output_to(string(HTMLString), print_html(Tokens)). 543 544list_clauses([]). 545list_clauses([H|T]) :- 546 ( system_undefined(H) 547 -> true 548 ; portray_clause(H) 549 ), 550 list_clauses(T). 551 552system_undefined((undefined :- tnot(undefined))). 553system_undefined((answer_count_restraint :- tnot(answer_count_restraint))). 554system_undefined((radial_restraint :- tnot(radial_restraint))). 555 556dict_bindings(Dict, Bindings) :- 557 dict_pairs(Dict, _Tag, Pairs), 558 maplist([N-V,N=V]>>true, Pairs, Bindings). 559 560select_residuals([], [], [], [], []). 561select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 562 binding_residual(H, Var, Residual), 563 !, 564 Vars = [Var|TV], 565 Residuals = [Residual|TR], 566 select_residuals(T, Bindings, TV, TR, Clauses). 567select_residuals([H|T], Bindings, Vars, Residuals, Clauses) :- 568 binding_residual_clauses(H, Var, Delays, Clauses0), 569 !, 570 Vars = [Var|TV], 571 Residuals = [Delays|TR], 572 append(Clauses0, CT, Clauses), 573 select_residuals(T, Bindings, TV, TR, CT). 574select_residuals([H|T0], [H|T], Vars, Residuals, Clauses) :- 575 select_residuals(T0, T, Vars, Residuals, Clauses). 576 577binding_residual('_residuals' = '$residuals'(Residuals), '_residuals', Residuals) :- 578 is_list(Residuals). 579binding_residual('Residuals' = '$residuals'(Residuals), 'Residuals', Residuals) :- 580 is_list(Residuals). 581binding_residual('Residual' = '$residual'(Residual), 'Residual', [Residual]) :- 582 callable(Residual). 583 584binding_residual_clauses( 585 '_wfs_residual_program' = '$wfs_residual_program'(Delays, Clauses), 586 '_wfs_residual_program', Residuals, Clauses) :- 587 phrase(delay_list(Delays), Residuals). 588 589delay_list(true) --> !. 590delay_list((A,B)) --> !, delay_list(A), delay_list(B). 591delay_list(M:A) --> !, [M:'$wfs_undefined'(A)]. 592delay_list(A) --> ['$wfs_undefined'(A)]. 593 594add_projection(-, _, JSON, JSON) :- !. 595add_projection(VarNames0, ResVars0, JSON0, JSON) :- 596 append(ResVars0, ResVars1), 597 sort(ResVars1, ResVars), 598 subtract(VarNames0, ResVars, VarNames), 599 add_projection(VarNames, JSON0, JSON).
610binding_to_html(ID, binding(Vars,Term,Substitutions), JSON) :- 611 JSON0 = json{variables:Vars, value:HTMLString}, 612 binding_write_options(ID, Options), 613 term_html_string(Term, Vars, ID, HTMLString, Options), 614 ( Substitutions == [] 615 -> JSON = JSON0 616 ; maplist(subst_to_html(ID), Substitutions, HTMLSubst), 617 JSON = JSON0.put(substitutions, HTMLSubst) 618 ). 619 620binding_write_options(Pengine, Options) :- 621 ( current_predicate(Pengine:screen_property/1), 622 Pengine:screen_property(tabled(true)) 623 -> Options = [] 624 ; Options = [priority(699)] 625 ).
634term_html_string(Term, Vars, Module, HTMLString, Options) :-
635 setting(write_options, WOptions),
636 merge_options(WOptions,
637 [ quoted(true),
638 numbervars(true),
639 module(Module)
640 | Options
641 ], WriteOptions),
642 phrase(term_html(Term, Vars, WriteOptions), Tokens),
643 with_output_to(string(HTMLString), print_html(Tokens)).655:- multifile binding_term//3. 656 657term_html(Term, Vars, WriteOptions) --> 658 { nonvar(Term) }, 659 binding_term(Term, Vars, WriteOptions), 660 !. 661term_html(Undef, _Vars, WriteOptions) --> 662 { nonvar(Undef), 663 Undef = '$wfs_undefined'(Term), 664 ! 665 }, 666 html(span(class(wfs_undefined), \term(Term, WriteOptions))). 667term_html(Term, _Vars, WriteOptions) --> 668 term(Term, WriteOptions).
675subst_to_html(ID, '$VAR'(Name)=Value, json{var:Name, value:HTMLString}) :- 676 !, 677 binding_write_options(ID, Options), 678 term_html_string(Value, [Name], ID, HTMLString, Options). 679subst_to_html(_, Term, _) :- 680 assertion(Term = '$VAR'(_)).
687map_output(ID, message(Term, Kind, HTMLString, Src), JSON) :- 688 atomic(HTMLString), 689 !, 690 JSON0 = json{event:output, id:ID, message:Kind, data:HTMLString}, 691 pengines:add_error_details(Term, JSON0, JSON1), 692 ( Src = File:Line, 693 \+ JSON1.get(location) = _ 694 -> JSON = JSON1.put(_{location:_{file:File, line:Line}}) 695 ; JSON = JSON1 696 ). 697map_output(ID, Term, json{event:output, id:ID, data:Data}) :- 698 ( atomic(Term) 699 -> Data = Term 700 ; is_dict(Term, json), 701 ground(json) % TBD: Check proper JSON object? 702 -> Data = Term 703 ; term_string(Term, Data) 704 ).
711:- multifile 712 prolog_help:show_html_hook/1. 713 714prolog_helpshow_html_hook(HTML) :- 715 pengine_output, 716 pengine_output(HTML). 717 718 719 /******************************* 720 * SANDBOXING * 721 *******************************/ 722 723:- multifile 724 sandbox:safe_primitive/1, % Goal 725 sandbox:safe_meta/2. % Goal, Called 726 727sandbox:safe_primitive(pengines_io:pengine_listing(_)). 728sandbox:safe_primitive(pengines_io:pengine_nl). 729sandbox:safe_primitive(pengines_io:pengine_tab(_)). 730sandbox:safe_primitive(pengines_io:pengine_flush_output). 731sandbox:safe_primitive(pengines_io:pengine_print(_)). 732sandbox:safe_primitive(pengines_io:pengine_write(_)). 733sandbox:safe_primitive(pengines_io:pengine_read(_)). 734sandbox:safe_primitive(pengines_io:pengine_read_line_to_string(_,_)). 735sandbox:safe_primitive(pengines_io:pengine_read_line_to_codes(_,_)). 736sandbox:safe_primitive(pengines_io:pengine_write_canonical(_)). 737sandbox:safe_primitive(pengines_io:pengine_write_term(_,_)). 738sandbox:safe_primitive(pengines_io:pengine_writeln(_)). 739sandbox:safe_primitive(pengines_io:pengine_writeq(_)). 740sandbox:safe_primitive(pengines_io:pengine_portray_clause(_)). 741sandbox:safe_primitive(system:write_term(_,_)). 742sandbox:safe_primitive(system:prompt(_,_)). 743sandbox:safe_primitive(system:statistics(_,_)). 744 745sandbox:safe_meta(pengines_io:pengine_format(Format, Args), Calls) :- 746 sandbox:format_calls(Format, Args, Calls). 747 748 749 /******************************* 750 * REDEFINITION * 751 *******************************/
758pengine_io_predicate(writeln(_)). 759pengine_io_predicate(nl). 760pengine_io_predicate(tab(_)). 761pengine_io_predicate(flush_output). 762pengine_io_predicate(format(_)). 763pengine_io_predicate(format(_,_)). 764pengine_io_predicate(read(_)). 765pengine_io_predicate(read_line_to_string(_,_)). 766pengine_io_predicate(read_line_to_codes(_,_)). 767pengine_io_predicate(write_term(_,_)). 768pengine_io_predicate(write(_)). 769pengine_io_predicate(writeq(_)). 770pengine_io_predicate(display(_)). 771pengine_io_predicate(print(_)). 772pengine_io_predicate(write_canonical(_)). 773pengine_io_predicate(listing). 774pengine_io_predicate(listing(_)). 775pengine_io_predicate(portray_clause(_)). 776 777term_expansion(pengine_io_goal_expansion(_,_), 778 Clauses) :- 779 findall(Clause, io_mapping(Clause), Clauses). 780 781io_mapping(pengine_io_goal_expansion(Head, Mapped)) :- 782 pengine_io_predicate(Head), 783 Head =.. [Name|Args], 784 atom_concat(pengine_, Name, BodyName), 785 Mapped =.. [BodyName|Args]. 786 787pengine_io_goal_expansion(_, _). 788 789 790 /******************************* 791 * REBIND PENGINE I/O * 792 *******************************/ 793 794:- public 795 stream_write/2, 796 stream_read/2, 797 stream_close/1. 798 799:- thread_local 800 pengine_io/2. 801 802stream_write(Stream, Out) :- 803 ( pengine_io(_,_) 804 -> send_html(pre(class(console), Out)) 805 ; current_prolog_flag(pengine_main_thread, TID), 806 thread_signal(TID, stream_write(Stream, Out)) 807 ). 808stream_read(Stream, Data) :- 809 ( pengine_io(_,_) 810 -> prompt(Prompt, Prompt), 811 pengine_input(_{type:console, prompt:Prompt}, Data) 812 ; current_prolog_flag(pengine_main_thread, TID), 813 call_in_thread(TID, stream_read(Stream, Data)) 814 ). 815stream_close(_Stream).
825pengine_bind_user_streams :- 826 Err = Out, 827 open_prolog_stream(pengines_io, write, Out, []), 828 set_stream(Out, buffer(line)), 829 open_prolog_stream(pengines_io, read, In, []), 830 set_stream(In, alias(user_input)), 831 set_stream(Out, alias(user_output)), 832 set_stream(Err, alias(user_error)), 833 set_stream(In, alias(current_input)), 834 set_stream(Out, alias(current_output)), 835 assertz(pengine_io(In, Out)), 836 thread_self(Me), 837 thread_property(Me, id(Id)), 838 set_prolog_flag(pengine_main_thread, Id), 839 thread_at_exit(close_io). 840 841close_io :- 842 retract(pengine_io(In, Out)), 843 !, 844 close(In, [force(true)]), 845 close(Out, [force(true)]). 846close_io.
853pengine_output :- 854 current_output(Out), 855 pengine_io(_, Out). 856 857pengine_input :- 858 current_input(In), 859 pengine_io(In, _).
867pengine_bind_io_to_html(Module) :- 868 forall(pengine_io_predicate(Head), 869 bind_io(Head, Module)), 870 pengine_bind_user_streams. 871 872bind_io(Head, Module) :- 873 prompt(_, ''), 874 redefine_system_predicate(Module:Head), 875 functor(Head, Name, Arity), 876 Head =.. [Name|Args], 877 atom_concat(pengine_, Name, BodyName), 878 Body =.. [BodyName|Args], 879 assertz(Module:(Head :- Body)), 880 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).*/