1:- module(pwp, 2 [ pwp_files/2, % +FileIn, +FileOut 3 pwp_stream/3, % +StreamIn, +StreamOut, +Context 4 pwp_xml/3 % +DomIn, -DOMOut, +Context 5 ]). 6 7/** <module> Prolog Well-formed Pages 8 9PWP is an approach to server-side scripting using Prolog 10which is based on a simple key principle: 11 12 - The source form of a PWP should be WELL-FORMED XML 13 14Especially when generating XML rather than HTML, this is such an 15obvious thing to do. We have many kinds of XML checking tools. 16 17 - We can tell whether an XML document is WELL FORMED (all the 18 punctuation is right, all tags balance) using practically 19 any decent parser, including SWI Prolog's 'sgml'. 20 21 - If we can write a Document Type Description then we can check 22 that a document is VALID using tools like Open SP (formerly 23 James Clark's SP) or SWI Prolog's 'sgml'. This does not 24 guarantee that the output will be valid, but it does catch 25 a lot of errors very early. 26 27 - If we can write an XML Schema then we can check that a 28 document is schema-valid. (SWI Prolog's 'sgml' does not 29 yet come with a schema validator, but who knows what the 30 future holds?). 31 32 - Since an XML document is just a data structure, we can use 33 any checking tool that we can write in Prolog, IF the input 34 is well-formed so that we can load a template as a Prolog 35 data structure. 36 37Having decided that the input should be well formed, that means 38*|NO NEW SYNTAX|* 39 40None of the weird and horrible <% ... %> or whatever not-quite-XML 41stuff you see in other template systems, making checking so very hard 42(and therefore, making errors so distressingly common). 43 44That in turns means that PWP "markup" must be based on special 45elements or special attributes. The fact that an XML parser must 46allow undeclared attributes on any element even when validating, 47but must not allow undeclared elements, suggests doing this through 48attributes. In particular, one should be able to take an existing 49DTD, such as an XHTML DTD, and just use that without modification. 50So the design reduces to 51 52 - Allow dynamic data selection, insertion, and transformation 53 just using a small number of extra attributes. 54 55This description uses the following name space: 56 57 == 58 xmlns:pwp='http://www.cs.otago.ac.nz/staffpriv/ok/pwp.pl' 59 == 60 61The attributes are 62 63 - pwp:ask = Query 64 - pwp:use = Term 65 - pwp:how = text | xml 66 - pwp:tag = QName or '-' 67 - pwp:att = '' | 'one non-alphanumeric character' 68 69Here's what they mean. Each element is expanded in the context 70of a set of variable bindings. After expansion, if the tag is 71not mapped to '-', all attributes in the pwp: namespace are removed 72and the children elements are recursively expanded. 73 74 * pwp:ask = Query 75 76 * Query is a Prolog goal. For each solution of Query, the element 77 is further processed with the new variables of Query added to 78 the context. 79 80 * If Query is not a well formed Prolog goal, or if execution of 81 Query throws an exception, page transformation comes to a complete 82 halt and no page is generated. 83 84 * pwp:use = Term 85 * pwp:how = text | xml | text-file | xml-file | pwp-file 86 87 Term is a Prolog term; variables in Term are bound by the context. 88 An empty Term is regarded as a missing value for this attribute. 89 The Prolog variable CONTEXT refers to the entire context, a list 90 of Name = Value, where Name is a Prolog atom holding the name of the context variable and Value is an arbitrary Prolog term. 91 92 - If pwp:how is text, 93 The value of Term is used to define a sequence of characters. 94 95 - A number produces the same characters that write/1 would. 96 - An atom produces the same characters that write/1 would. 97 - A string produces the same characters that write/1 would. 98 - A list of character codes produces those characters. 99 100 - The following terms produce the same sequence of characters 101 that the corresponding goal would have sent to the current 102 output stream: 103 104 - write(Datum) 105 - writeq(Datum) 106 - write_canonical(Datum) 107 - print(Datum) 108 - print(Datum) 109 - format(Format) 110 - format(Format, Arguments) 111 112 - A singleton list [X] defines the characters that X defines. 113 - Any other term F(T1,...,Tn) defines the characters that T1 114 defines, followed by the characters that T2 defines, ..., 115 followed by the characters that Tn defines. 116 117 - If pwp:how is xml, 118 The value of Term must be an XML term as defined in the 119 SGML2PL documentation or a list of such terms. A single 120 term is taken as if it had been [Term]. The resulting 121 list of terms replaces the children of the current element 122 and will not be further processed. 123 124 - If pwp:how is text-file, 125 The value of Term is used to define a sequence of characters. 126 That sequence of characters is used as a file name. 127 The file is read as a sequence of characters, and that 128 sequence used as character data. 129 130 - If pwp:how is xml-file, 131 The value of Term is used to define a sequence of characters. 132 That sequence of characters is used as a file name. 133 The file is loaded as XML, and the sequence of XML items thus 134 obtained used. This means that PWP provides XML inclusion 135 without depending on the parser to support XInclude. 136 137 - If pwp:how is pwp-file, 138 Like xml-file, but PWP attributes are evaluated and processed. 139 The current context variables are passed to the PWP processor. 140 141 The default value for pwp:how is text. 142 143 * pwp:tag = QName or '-' 144 145 If pwp:tag is missing or the value is empty, the current element 146 appears in the output (after further processing) with its present 147 tag. If pwp:tag is a QName, the current element appears (...) 148 with that as its tag. That option is most useful in DTDs, where 149 an "authoring" DTD may use one tag and have it automatically mapped 150 to another tag in the output, e.g., <item> -> <li>. Finally, if 151 pwp:tag is '-', the children of the current element (either the 152 result of pwp:use or the transformed original children, whichever 153 applies) appear in the output but there is no element around them. 154 155 A missing or empty pwp:ask is just like pwp:ask = 'true'. 156 157 * pwp:att = '' | 'one non-alphanumeric character'. 158 159 Attributes in the pwp namespace are not affected by this attribute. 160 Such attributes are always stripped out and never substituted into. 161 162 If pwp:att is missing or empty, attributes of the current 163 element are copied over to the output unchanged. 164 165 If pwp:att = 'c' for some non-alphanumeric character c, 166 each attribute is examined for occurrences of c(...)c and c[...]c 167 which are as short as possible. 168 There is no one character which could be used every time, so you 169 have to explicitly choose a substitution marker which is safe 170 for the data you do not want to be altered. None of the pwp 171 attributes are inherited, least of all this one. 172 173 Text outside c(...)c groups is copied unchanged; text inside 174 a c(...)c group is parsed as a Prolog term and treated as if by 175 pwp:how = text. Text inside a c[...]c group is evaluated (in the 176 current context), and if it fails, the entire attribute will be 177 removed from the element. 178 179 180Examples: 181 182 1. *|A "Hello World" like example|* 183 184 == 185 <html 186 xmlns:pwp="http://www.cs.otago.ac.nz/staffpriv/ok/pwp.pl" 187 pwp:ask = "ensure_loaded(msg), once(msg(Greeting))"> 188 <head> 189 <title pwp:use="Greeting"/> 190 </head> 191 <body> 192 <p><span pwp:use="Greeting" pwp:tag='-'/></p> 193 </body> 194 </html> 195 == 196 197 where msg.pl contains 198 199 == 200 msg('Hello, World!'). 201 == 202 203 This example illustrates an important point. Prolog Well-Formed 204 Pages provide *NO* way to physically incorporate Prolog *clauses* 205 into a page template. Prolog clauses must be put in separate 206 files which can be checked by a Prolog syntax checker, compiler, 207 cross-referencer, &c WITHOUT the Prolog tool in question needing 208 to know anything whatsoever about PWP. You load the files using 209 pwp:ask on the root element. 210 211 2. *|Binding some variables and using them|* 212 213 == 214 <html 215 xmlns:pwp="http://www.cs.otago.ac.nz/staffpriv/ok/pwp.pl"> 216 <head><title>Example 2</title></head> 217 <body pwp:ask="Hello = 'Hello world', A = 20, B = 22"> 218 <h1 pwp:use="Hello"/> 219 <p>The answer is <span pwp:use="C" pwp:ask="C is A+B"/>.</p> 220 </body> 221 </html> 222 == 223 224 3. *|Making a table|* 225 We are given a Prolog database staff.pl defining 226 staff(NickName, FullName, Office, Phone, E_Mail_Address). 227 status(NickName, full_time | part_time). 228 We want to make a phone list of full time staff. 229 230 == 231 <html 232 xmlns:pwp="http://www.cs.otago.ac.nz/staffpriv/ok/pwp.pl" 233 pwp:ask='ensure_loaded(staff)'> 234 <head> 235 <title>Phone list for Full-Time staff.</title> 236 </head> 237 <body> 238 <h1>Phone list for Full-Time staff.</h1> 239 <table 240 pwp:ask = "setof(FullName-Phone, 241 N^O^E^( 242 status(N, full_time), 243 staff(N, FullName, O, Phone, E) 244 ), 245 Staff_List)"> 246 <tr><th>Name</th><th>Phone</th></tr> 247 <tr pwp:ask="member(FullName-Phone, Staff_List)"> 248 <td pwp:use="FullName"/> 249 <td pwp:use="Phone"/> 250 </tr> 251 </table> 252 </body> 253 </html> 254 == 255 256 4. *|Substituting into an attribute|* 257 Same data base as before, but now we want to make a mailing list 258 page. 259 260 == 261 <html 262 xmlns:pwp="http://www.cs.otago.ac.nz/staffpriv/ok/pwp.pl" 263 pwp:ask='ensure_loaded(staff)'> 264 <head> 265 <title>Phone list for Full-Time staff.</title> 266 </head> 267 <body> 268 <h1>Phone list for Full-Time staff.</h1> 269 <table 270 pwp:ask = "setof(FullName-E_Mail, 271 N^O^P^staff(N, FullName, O, P, E_Mail), 272 Staff_List)"> 273 <tr><th>Name</th><th>Address</th></tr> 274 <tr pwp:ask="member(FullName-E_Mail, Staff_List)"> 275 <td pwp:use="FullName"/> 276 <td><a pwp:use="E_Mail" 277 pwp:att='$' href="mailto:$(E_Mail)$"/></td> 278 </tr> 279 </table> 280 </body> 281 </html> 282 == 283 284 5. *|If-then-else effect|* 285 A page that displays the value of the 'SHELL' environment 286 variable if it has one, otherwise displays 'There is no 287 default shell.' 288 289 == 290 <html 291 xmlns:pwp="http://www.cs.otago.ac.nz/staffpriv/ok/pwp.pl"> 292 <head><title>$SHELL</title></head> 293 <body> 294 <p pwp:ask="getenv('SHELL', Shell)" 295 >The default shell is <span pwp:tag="-" pwp:use="Shell"/>.</p> 296 <p pwp:ask="\+getenv('SHELL',_)">There is no default shell.</p> 297 </body> 298 </html> 299 == 300 301 There is one other criterion for a good server-side template 302 language: 303 304 It should be possible to compile templates so as to eliminate 305 most if not all interpretation overhead. 306 307 This particular notation satisfies that criterion with the 308 limitation that the conversion of a term to character data requires 309 run-time traversal of terms (because the terms are not known until 310 run time). 311 312@author Richard O'Keefe 313@tbd Support compilation of PWP input files 314*/ 315 316:- use_module(library(sgml), [load_xml_file/2]). 317:- use_module(library(sgml_write), [xml_write/3]). 318:- use_module(library(lists), [append/3]). 319 320:- meta_predicate 321 pwp_files(, ), 322 pwp_stream(, , ), 323 pwp_xml(, , ). 324 325 326%% pwp_files(:In:atom, +Out:atom) is det. 327% 328% loads an Xml document from the file named In, 329% transforms it using the PWP attributes, and 330% writes the transformed version to the new file named Out. 331 332pwp_files(M:In, Out) :- 333 load_xml_file(In, Contents), 334 pwp_xml(M:Contents, Transformed, []), 335 !, 336 setup_call_cleanup(open(Out, write, Output), 337 xml_write(Output, Transformed, []), 338 close(Output)). 339 340 341%! pwp_stream(:Input:input_stream, +Output:output_stream, 342%! +Context:list) is det. 343% 344% Loads an Xml document from the given Input stream, transforms it 345% using the PWP attributes, and writes the transformed version to 346% the given Output stream. Context provides initial contextual 347% variables and is a list of Name=Value. 348 349pwp_stream(M:Input, Output, Context) :- 350 load_xml_file(stream(Input), Contents), 351 pwp_xml(M:Contents, Transformed, Context), 352 !, 353 xml_write(Output, Transformed, []). 354 355 356/* Recall that an XML term is one of 357 358 <atom> Character Data 359 sdata(...) SDATA (SGML only) 360 ndata(...) NDATA 361 pi(...) Processing instruction 362 363 element(Name, [Att...], [Child...]) 364 365 where Att is Attribute=Value and Child is an XML term. 366 367 We are only concerned with elements; all other XML terms are 368 left alone. I have given some thought to recognising 369 370 <?pwp ...Command...?> 371 372 processing instructions, executing the Command, and removing 373 the processing instructions, as a debugging tool. But this 374 is a proof-of-concept implementation; debugging features can 375 wait for The Real Thing. 376*/ 377 378 379 380%% pwp_xml(:In:list(xml), -Out:list(xml), +Context) 381% 382% maps down a list of XML items, acting specially on elements and 383% copying everything else unchanged, including white space. 384% The Context is a list of 'VariableName'=CurrentValue bindings. 385 386pwp_xml(M:In, Out, Context) :- 387 pwp_list(In, Out, M, Context). 388 389pwp_list([], [], _, _). 390pwp_list([element(Tag0,Atts0,Kids0)|Xs], Ys0, M, Context) :- 391 !, 392 pwp_attributes(Atts0, Ask, Use, How, Att, Tag1, Atts1), 393 ( nonvar(Tag1), Tag1 \== '' -> Tag2 = Tag1 394 ; Tag2 = Tag0 395 ), 396 ( nonvar(Ask), Ask \== '', Ask \== 'true' 397 -> atom_to_term(Ask, Query, Bindings), 398 pwp_unite(Bindings, Context, Context1), 399 findall(Xml, 400 ( M:Query, 401 pwp_element(Tag2, Atts1, Kids0, Use, How, Att, 402 M, Context1, Xml)), 403 NewContent) 404 ; /* Ask is missing, empty, or true */ 405 pwp_element(Tag2, Atts1, Kids0, Use, How, Att, 406 M, Context, NewContent) 407 ), 408 pwp_attach(NewContent, Ys0, Ys1), 409 pwp_list(Xs, Ys1, M, Context). 410pwp_list([X|Xs], [X|Ys], M, Context) :- 411 pwp_list(Xs, Ys, M, Context). 412 413 414%! pwp_attributes(+Atts0:list(=(atom,atom)), 415%! -Ask:atom, -Use:atom, -How:atom, -Att:atom, 416%! -Tag:atom, -Atts1:list(=(atom,atom))) 417% 418% Walks down a list of AttributeName=ItsValue pairs, stripping out 419% those whose AttributeName begins with the 'pwp:' prefix, and 420% copying the rest to Atts1. Along the way, Ask/Use/How/Att/Tag 421% are bound to the values of the 422% pwp:ask/pwp:use/pwp:how/pwp:att/pwp:tag attributes, if any. At 423% the end, any of these variables that are still unbound REMAIN 424% unbound; they are not bound to default values. 425 426pwp_attributes([], _, _, _, _, _, []). 427pwp_attributes([AV|AVs], Ask, Use, How, Att, Tag, New_Atts1) :- 428 AV = (Name=Value), 429 ( pwp_attr(Name, PWPName) 430 -> ( pwp_attr(PWPName, Value, Ask, Use, How, Att, Tag) 431 -> New_Atts1 = New_Atts2 432 ; New_Atts1 = New_Atts2 433 ) 434 ; New_Atts1 = [AV|New_Atts2] 435 ), 436 pwp_attributes(AVs, Ask, Use, How, Att, Tag, New_Atts2). 437 438 439pwp_attr(ask, Value, Value, _Use, _How, _Att, _Tag). 440pwp_attr(use, Value, _Ask, Value, _How, _Att, _Tag). 441pwp_attr(how, Value, _Ask, _Use, Value, _Att, _Tag). 442pwp_attr(att, Value, _Ask, _Use, _How, Value, _Tag). 443pwp_attr(tag, Value, _Ask, _Use, _How, _Att, Value). 444 445%! pwp_attr(+XMLAttr, -PWPLocal) is semidet. 446% 447% True if PWPLocal is the local name of a pwp:Local expression in 448% XML. This predicate deals with the three different XML 449% representations: the form is returned of XML namespace 450% processing is not enabled. The second if it is enabled and the 451% namespace is properly defined and the last if the namespace is 452% not defined. 453 454pwp_attr(Atom, PWP) :- 455 atom(Atom), 456 atom_concat('pwp:', PWP, Atom), 457 !. 458pwp_attr('http://www.cs.otago.ac.nz/staffpriv/ok/pwp.pl':PWP, PWP) :- !. 459pwp_attr('pwp':PWP, PWP) :- !. 460pwp_attr('xmlns:pwp', -). 461 462%% pwp_unite(+Bindings, +Context0, -Context:list(=(atom,any))) 463% 464% merges the new Bindings with the bindings in the outer Context0, 465% constructing a new list of VariableName=CurrentValue bindings in 466% Context1. This is only used when the CurrentValue parts of the 467% new Bindings are known to be distinct new variables, so the 468% Bindings cannot possibly conflict with any existing binding in 469% Context0. This is O(|Bindings|.|Context0|), which is not that 470% efficient, but since we do not expect there to be very many 471% variables it doesn't matter much. 472 473pwp_unite(Bindings, Context0, Context) :- 474 pwp_unite(Bindings, Context0, Context0, Context). 475 476 477pwp_unite([], _, Context, Context). 478pwp_unite([Binding|Bindings], Context0, Context1, Context) :- 479 memberchk(Binding, Context0), 480 !, 481 pwp_unite(Bindings, Context0, Context1, Context). 482pwp_unite(['CONTEXT'=Context0|Bindings], Context0, Context1, Context) :- 483 !, 484 pwp_unite(Bindings, Context0, Context1, Context). 485pwp_unite([Binding|Bindings], Context0, Context1, Context) :- 486 pwp_unite(Bindings, Context0, [Binding|Context1], Context). 487 488 489 490%% pwp_unite(+Bindings, +Context0: list(=(atom,any))) 491% 492% looks up the bindings in Bindings in the outer Context0. 493% This is only used for 'pwp:use' terms (and the related terms 494% in $(...)$ attribute value substitutions), so that we have 495% no interest in forming a new context. (If we did, we'd use 496% pwp_unite/3 instead.) This is only used when the CurrentValue 497% parts of the new Bindings are known to be distinct new variables, 498% so the Bindings cannot possibly conflict with any existing 499% binding in Context0. However, there _could_ be new variables 500% in Bindings, and that would cause problems. An XML term may 501% not contain variables, and a term we want to convert to a list 502% of character codes had better not contain variables either. 503% One approach would be to just bind such variables to something, 504% another is to throw some kind of exception. For the moment we 505% call functor/3 so as to get an instantiation error. 506 507pwp_unite([], _). 508pwp_unite([Binding|Bindings], Context) :- 509 memberchk(Binding, Context), 510 !, 511 pwp_unite(Bindings, Context). 512pwp_unite([_=Value|_], _) :- 513 functor(Value, _, _). 514 515%% pwp_attach(+Tree, ?Ys0: list(xml), ?Ys: list(xml)) 516% 517% is a combination of "flatten" and "append". 518% It unifies Ys0\Ys with the result of flattening Tree. 519 520pwp_attach([], Ys, Ys) :- !. 521pwp_attach([X|Xs], Ys0, Ys) :- 522 !, 523 pwp_attach(X, Ys0, Ys1), 524 pwp_attach(Xs, Ys1, Ys). 525pwp_attach(X, [X|Ys], Ys). 526 527 528 529pwp_element('-', _, Kids, Use, How, _, M, Context, Xml) :- 530 !, 531 pwp_use(Use, How, Kids, M, Context, Xml). 532pwp_element(Tag, Atts, [Value], Use, How, Magic, M, Context, 533 element(Tag,Atts1,Kids1)) :- 534 verbatim_element(Tag), nonvar(Magic), atomic(Value), 535 !, 536 %% Apply substition of c(..)c variables also to content of 537 %% <script> and <style> tags: 538 pwp_substitute([cdata=Value|Atts], Magic, Context, 539 [cdata=Value1|Atts1]), 540 pwp_use(Use, How, [Value1], M, Context, Kids1). 541pwp_element(Tag, Atts, Kids, Use, How, Magic, M, Context, 542 element(Tag,Atts1,Kids1)) :- 543 ( nonvar(Magic) 544 -> pwp_substitute(Atts, Magic, Context, Atts1) 545 ; Atts1 = Atts 546 ), 547 pwp_use(Use, How, Kids, M, Context, Kids1). 548 549pwp_use('', _, Kids, M, Context, Kids1) :- 550 !, 551 pwp_list(Kids, Kids1, M, Context). 552pwp_use(Use, How, _, M, Context, Kids1) :- 553 atom_to_term(Use, Term, Bindings), 554 pwp_unite(Bindings, Context), 555 pwp_how(How, Term, M, Context, Kids1). 556 557pwp_how('text', Term, _,_, [CData]) :- 558 !, 559 pwp_use_codes(Term, Codes, []), 560 atom_codes(CData, Codes). 561pwp_how('xml', Term, _,_, Kids1) :- 562 ( Term == [] -> Kids1 = Term 563 ; Term = [_|_] -> Kids1 = Term 564 ; Kids1 = [Term] 565 ). 566pwp_how('text-file', Term, _,_, [CData]) :- 567 pwp_use_codes(Term, Codes, []), 568 atom_codes(FileName, Codes), 569 read_file_to_codes(FileName, FileCodes, []), 570 atom_codes(CData, FileCodes). 571pwp_how('xml-file', Term, _,_, Kids1) :- 572 pwp_use_codes(Term, Codes, []), 573 atom_codes(FileName, Codes), 574 load_xml_file(FileName, Kids1). 575pwp_how('pwp-file', Term, M,Context, Kids1) :- 576 pwp_use_codes(Term, Codes, []), 577 atom_codes(FileName, Codes), 578 ( memberchk('SCRIPT_DIRECTORY'=ScriptDir,Context) -> true 579 ; ScriptDir='.' 580 ), 581 absolute_file_name(FileName, PathName, [relative_to(ScriptDir)]), 582 load_xml_file(PathName, Kids0), 583 pwp_xml(M:Kids0, Kids1, Context), 584 !. 585 586 587pwp_substitute([], _, _, []). 588pwp_substitute([AV|AVs], Magic, Context, NewAvs) :- 589 AV = (Name = Value), 590 ( sub_atom(Value, _, _, _, Magic) 591 -> char_code(Magic, C), 592 atom_codes(Value, Codes), 593 pwp_split(Codes, C, B0, T0, A0, Type), 594 !, 595 ( pwp_substitute(B0, T0, A0, C, Context, V, Type) 596 -> NewAvs = [AV1|Atts1], 597 atom_codes(New_Value, V), 598 AV1 = (Name = New_Value) 599 ; Type == existence-> 600 NewAvs = Atts1 601 ), 602 pwp_substitute(AVs, Magic, Context, Atts1) 603 ). 604pwp_substitute([AV|AVs], Magic, Context, [AV|Atts1]) :- 605 pwp_substitute(AVs, Magic, Context, Atts1). 606 607 608pwp_substitute(B0, T0, A0, C, Context, V0, Type) :- 609 append(B0, V1, V0), 610 atom_codes(Atom, T0), 611 atom_to_term(Atom, Term, Bindings), 612 pwp_unite(Bindings, Context, _), 613 ( Type == value 614 -> pwp_use_codes(Term, V1, V2) 615 ; catch(, _, fail), 616 V2 = V1 617 ), 618 ( pwp_split(A0, C, B1, T1, A1, T2) 619 -> pwp_substitute(B1, T1, A1, C, Context, V2, T2) 620 ; V2 = A0 621 ). 622 623 624pwp_split(Codes, C, Before, Text, After, Type) :- 625 append(Before, [C,C1|Rest], Codes), 626 ( C1 == 0'( 627 -> Type = value, 628 C2 = 0') 629 ; C1 == 0'[, 630 Type = existence, 631 C2 = 0'] 632 ), 633 append(Text, [C2,C|After], Rest), 634 !. 635 636pwp_use_codes(format(Format), S0, S) :- 637 !, 638 pwp_format(Format, [], S0, S). 639pwp_use_codes(format(Format,Args), S0, S) :- 640 !, 641 pwp_format(Format, Args, S0, S). 642pwp_use_codes(write_canonical(Datum), S0, S) :- 643 !, 644 pwp_format('~k', [Datum], S0, S). 645pwp_use_codes(print(Datum), S0, S) :- 646 !, 647 pwp_format('~p', [Datum], S0, S). 648pwp_use_codes(writeq(Datum), S0, S) :- 649 !, 650 pwp_format('~q', [Datum], S0, S). 651pwp_use_codes(write(Datum), S0, S) :- 652 !, 653 pwp_format('~w', [Datum], S0, S). 654pwp_use_codes(Atomic, S0, S) :- 655 atomic(Atomic), 656 !, 657 ( number(Atomic) -> number_codes(Atomic, Codes) 658 ; atom(Atomic) -> atom_codes(Atomic, Codes) 659 ; string(Atomic) -> string_codes(Atomic, Codes) 660 ; pwp_format('~w', [Atomic], S0, S) 661 ), 662 append(Codes, S, S0). 663pwp_use_codes([X|Xs], S0, S) :- 664 pwp_is_codes([X|Xs]), 665 !, 666 append([X|Xs], S, S0). 667pwp_use_codes([X|Xs], S0, S) :- 668 !, 669 pwp_use_codes(Xs, X, S0, S). 670pwp_use_codes(Compound, S0, S) :- 671 Compound =.. [_,X|Xs], 672 pwp_use_codes(Xs, X, S0, S). 673 674 675 676pwp_use_codes([], X, S0, S) :- 677 !, 678 pwp_use_codes(X, S0, S). 679pwp_use_codes([Y|Ys], X, S0, S) :- 680 pwp_use_codes(X, S0, S1), 681 pwp_use_codes(Ys, Y, S1, S). 682 683 684 685%% pwp_is_codes(+String: any) 686% 687% is true when String is a list of integers and each of those 688% integers is a possible Unicode value (in the range U+0000..U+10FFFF). 689% Back in the days of ISO Latin 1 we would have checked for 0..255, 690% and way back in the days of ASCII for 0..127. Yes, there are more 691% than a million possible characters in Unicode; currently about 692% 100 000 of them are in use. 693 694pwp_is_codes([]). 695pwp_is_codes([C|Cs]) :- 696 integer(C), C >= 0, C =< 0x10FFFF, 697 pwp_is_codes(Cs). 698 699pwp_format(Format, Arguments, S0, S) :- 700 format(codes(S0, S), Format, Arguments). 701 702 703verbatim_element(script). 704verbatim_element(style).