Replace.cpp

   1 /* Cycript - Inlining/Optimizing JavaScript Compiler
   2  * Copyright (C) 2009  Jay Freeman (saurik)
   3 */
   4
   5 /* Modified BSD License {{{ */
   6 /*
   7  *        Redistribution and use in source and binary
   8  * forms, with or without modification, are permitted
   9  * provided that the following conditions are met:
  10  *
  11  * 1. Redistributions of source code must retain the
  12  *    above copyright notice, this list of conditions
  13  *    and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the
  15  *    above copyright notice, this list of conditions
  16  *    and the following disclaimer in the documentation
  17  *    and/or other materials provided with the
  18  *    distribution.
  19  * 3. The name of the author may not be used to endorse
  20  *    or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS''
  24  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
  25  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  26  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
  28  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  29  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  30  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  31  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  33  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
  34  * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  35  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  36  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37 */
  38 /* }}} */
  39
  40 #include "Parser.hpp"
  41 #include "Replace.hpp"
  42
  43 #include <iomanip>
  44
  45 CYExpression *CYAdd::Replace(CYContext &context) {
  46     CYInfix::Replace(context);
  47
  48     CYExpression *lhp(lhs_->Primitive(context));
  49     CYExpression *rhp(rhs_->Primitive(context));
  50
  51     CYString *lhs(dynamic_cast<CYString *>(lhp));
  52     CYString *rhs(dynamic_cast<CYString *>(rhp));
  53
  54     if (lhs != NULL || rhs != NULL) {
  55         if (lhs == NULL) {
  56             lhs = lhp->String(context);
  57             if (lhs == NULL)
  58                 return this;
  59         } else if (rhs == NULL) {
  60             rhs = rhp->String(context);
  61             if (rhs == NULL)
  62                 return this;
  63         }
  64
  65         return lhs->Concat(context, rhs);
  66     }
  67
  68     if (CYNumber *lhn = lhp->Number(context))
  69         if (CYNumber *rhn = rhp->Number(context))
  70             return $D(lhn->Value() + rhn->Value());
  71
  72     return this;
  73 }
  74
  75 CYExpression *CYAddressOf::Replace(CYContext &context) {
  76     CYPrefix::Replace(context);
  77     return $C0($M(rhs_, $S("$cya")));
  78 }
  79
  80 void CYArgument::Replace(CYContext &context) { $T()
  81     context.Replace(value_);
  82     next_->Replace(context);
  83 }
  84
  85 CYExpression *CYArray::Replace(CYContext &context) {
  86     elements_->Replace(context);
  87     return this;
  88 }
  89
  90 CYExpression *CYArrayComprehension::Replace(CYContext &context) {
  91     CYVariable *cyv($V("$cyv"));
  92
  93     return $C0($F(NULL, $P1("$cyv", comprehensions_->Parameters(context)), $$->*
  94         $E($ CYAssign(cyv, $ CYArray()))->*
  95         comprehensions_->Replace(context, $E($C1($M(cyv, $S("push")), expression_)))->*
  96         $ CYReturn(cyv)
  97     ));
  98 }
  99
 100 CYExpression *CYAssignment::Replace(CYContext &context) {
 101     context.Replace(lhs_);
 102     context.Replace(rhs_);
 103     return this;
 104 }
 105
 106 CYStatement *CYBlock::Replace(CYContext &context) {
 107     statements_ = statements_->ReplaceAll(context);
 108     if (statements_ == NULL)
 109         return $ CYEmpty();
 110     return this;
 111 }
 112
 113 CYStatement *CYBreak::Replace(CYContext &context) {
 114     return this;
 115 }
 116
 117 CYExpression *CYCall::Replace(CYContext &context) {
 118     context.Replace(function_);
 119     arguments_->Replace(context);
 120     return this;
 121 }
 122
 123 namespace cy {
 124 namespace Syntax {
 125
 126 void Catch::Replace(CYContext &context) { $T()
 127     code_.Replace(context);
 128 }
 129
 130 } }
 131
 132 void CYClause::Replace(CYContext &context) { $T()
 133     context.Replace(case_);
 134     statements_ = statements_->ReplaceAll(context);
 135     next_->Replace(context);
 136 }
 137
 138 CYStatement *CYComment::Replace(CYContext &context) {
 139     return this;
 140 }
 141
 142 CYExpression *CYCompound::Replace(CYContext &context) {
 143     expressions_ = expressions_->ReplaceAll(context);
 144     return expressions_ == NULL ? NULL : this;
 145 }
 146
 147 CYFunctionParameter *CYComprehension::Parameters(CYContext &context) const { $T(NULL)
 148     CYFunctionParameter *next(next_->Parameters(context));
 149     if (CYFunctionParameter *parameter = Parameter(context)) {
 150         parameter->SetNext(next);
 151         return parameter;
 152     } else
 153         return next;
 154 }
 155
 156 CYStatement *CYComprehension::Replace(CYContext &context, CYStatement *statement) const {
 157     return next_ == NULL ? statement : next_->Replace(context, statement);
 158 }
 159
 160 CYExpression *CYCondition::Replace(CYContext &context) {
 161     context.Replace(test_);
 162     context.Replace(true_);
 163     context.Replace(false_);
 164     return this;
 165 }
 166
 167 CYStatement *CYContinue::Replace(CYContext &context) {
 168     return this;
 169 }
 170
 171 CYAssignment *CYDeclaration::Assignment(CYContext &context) {
 172     CYExpression *variable(Replace(context));
 173     return initialiser_ == NULL ? NULL : $ CYAssign(variable, initialiser_);
 174 }
 175
 176 CYExpression *CYDeclaration::ForEachIn(CYContext &context) {
 177     return $ CYVariable(identifier_);
 178 }
 179
 180 CYExpression *CYDeclaration::Replace(CYContext &context) {
 181     context.Replace(identifier_);
 182     context.scope_->Declare(context, identifier_, CYIdentifierVariable);
 183     return $ CYVariable(identifier_);
 184 }
 185
 186 CYProperty *CYDeclarations::Property(CYContext &context) { $T(NULL)
 187     return $ CYProperty(declaration_->identifier_, declaration_->initialiser_ ?: $U, next_->Property(context));
 188 }
 189
 190 CYCompound *CYDeclarations::Replace(CYContext &context) {
 191     CYCompound *compound;
 192     if (next_ == NULL) compound:
 193         compound = $ CYCompound();
 194     else {
 195         compound = next_->Replace(context);
 196         if (compound == NULL)
 197             goto compound;
 198     }
 199
 200     if (CYAssignment *assignment = declaration_->Assignment(context))
 201         compound->AddPrev(assignment);
 202     return compound;
 203 }
 204
 205 CYExpression *CYDirectMember::Replace(CYContext &context) {
 206     Replace_(context);
 207     return this;
 208 }
 209
 210 CYStatement *CYDoWhile::Replace(CYContext &context) {
 211     context.Replace(test_);
 212     context.Replace(code_);
 213     return this;
 214 }
 215
 216 void CYElement::Replace(CYContext &context) { $T()
 217     context.Replace(value_);
 218     next_->Replace(context);
 219 }
 220
 221 CYStatement *CYEmpty::Collapse(CYContext &context) {
 222     return next_;
 223 }
 224
 225 CYStatement *CYEmpty::Replace(CYContext &context) {
 226     return this;
 227 }
 228
 229 CYStatement *CYExpress::Collapse(CYContext &context) {
 230     if (CYExpress *express = dynamic_cast<CYExpress *>(next_)) {
 231         CYCompound *next(dynamic_cast<CYCompound *>(express->expression_));
 232         if (next == NULL)
 233             next = $ CYCompound(express->expression_);
 234         next->AddPrev(expression_);
 235         expression_ = next;
 236         SetNext(express->next_);
 237     }
 238
 239     return this;
 240 }
 241
 242 CYStatement *CYExpress::Replace(CYContext &context) {
 243     context.Replace(expression_);
 244     if (expression_ == NULL)
 245         return $ CYEmpty();
 246     return this;
 247 }
 248
 249 CYExpression *CYExpression::ClassName(CYContext &context, bool object) {
 250     return this;
 251 }
 252
 253 CYExpression *CYExpression::ForEachIn(CYContext &context) {
 254     return this;
 255 }
 256
 257 CYExpression *CYExpression::ReplaceAll(CYContext &context) { $T(NULL)
 258     CYExpression *replace(this);
 259     context.Replace(replace);
 260
 261     if (CYExpression *next = next_->ReplaceAll(context))
 262         replace->SetNext(next);
 263     else
 264         replace->SetNext(next_);
 265
 266     return replace;
 267 }
 268
 269 CYNumber *CYFalse::Number(CYContext &context) {
 270     return $D(0);
 271 }
 272
 273 CYString *CYFalse::String(CYContext &context) {
 274     return $S("false");
 275 }
 276
 277 void CYFinally::Replace(CYContext &context) { $T()
 278     code_.Replace(context);
 279 }
 280
 281 CYStatement *CYFor::Replace(CYContext &context) {
 282     context.Replace(initialiser_);
 283     context.Replace(test_);
 284     context.Replace(increment_);
 285     context.Replace(code_);
 286     return this;
 287 }
 288
 289 CYStatement *CYForIn::Replace(CYContext &context) {
 290     // XXX: this actually might need a prefix statement
 291     context.Replace(initialiser_);
 292     context.Replace(set_);
 293     context.Replace(code_);
 294     return this;
 295 }
 296
 297 CYFunctionParameter *CYForInComprehension::Parameter(CYContext &context) const {
 298     return $ CYFunctionParameter(name_);
 299 }
 300
 301 CYStatement *CYForInComprehension::Replace(CYContext &context, CYStatement *statement) const {
 302     return $ CYForIn($ CYVariable(name_), set_, CYComprehension::Replace(context, statement));
 303 }
 304
 305 CYStatement *CYForEachIn::Replace(CYContext &context) {
 306     CYVariable *cys($V("$cys")), *cyt($V("$cyt"));
 307
 308     return $ CYLet($L2($L($I("$cys"), set_), $L($I("$cyt"))), $$->*
 309         $ CYForIn(cyt, cys, $ CYBlock($$->*
 310             $E($ CYAssign(initialiser_->ForEachIn(context), $M(cys, cyt)))->*
 311             code_
 312         ))
 313     );
 314 }
 315
 316 CYFunctionParameter *CYForEachInComprehension::Parameter(CYContext &context) const {
 317     return $ CYFunctionParameter(name_);
 318 }
 319
 320 CYStatement *CYForEachInComprehension::Replace(CYContext &context, CYStatement *statement) const {
 321     CYVariable *cys($V("$cys")), *name($ CYVariable(name_));
 322
 323     return $E($C0($F(NULL, $P1("$cys"), $$->*
 324         $E($ CYAssign(cys, set_))->*
 325         $ CYForIn(name, cys, $ CYBlock($$->*
 326             $E($ CYAssign(name, $M(cys, name)))->*
 327             CYComprehension::Replace(context, statement)
 328         ))
 329     )));
 330 }
 331
 332 void CYFunction::Inject(CYContext &context) {
 333     context.Replace(name_);
 334     context.scope_->Declare(context, name_, CYIdentifierOther);
 335 }
 336
 337 void CYFunction::Replace_(CYContext &context, bool outer) {
 338     if (outer)
 339         Inject(context);
 340
 341     CYScope scope;
 342     scope.parent_ = context.scope_;
 343     context.scope_ = &scope;
 344
 345     if (!outer && name_ != NULL)
 346         Inject(context);
 347
 348     parameters_ = parameters_->Replace(context, code_);
 349     code_.Replace(context);
 350
 351     context.scope_ = scope.parent_;
 352     scope.Scope(context, code_.statements_);
 353 }
 354
 355 CYExpression *CYFunctionExpression::Replace(CYContext &context) {
 356     Replace_(context, false);
 357     return this;
 358 }
 359
 360 CYFunctionParameter *CYFunctionParameter::Replace(CYContext &context, CYBlock &code) {
 361     name_ = name_->Replace(context);
 362     context.scope_->Declare(context, name_, CYIdentifierArgument);
 363     if (next_ != NULL)
 364         next_ = next_->Replace(context, code);
 365     return this;
 366 }
 367
 368 CYStatement *CYFunctionStatement::Replace(CYContext &context) {
 369     Replace_(context, true);
 370     return this;
 371 }
 372
 373 CYIdentifier *CYIdentifier::Replace(CYContext &context) {
 374     if (replace_ != NULL && replace_ != this)
 375         return replace_->Replace(context);
 376     replace_ = context.scope_->Lookup(context, this);
 377     return replace_;
 378 }
 379
 380 CYStatement *CYIf::Replace(CYContext &context) {
 381     context.Replace(test_);
 382     context.Replace(true_);
 383     context.Replace(false_);
 384     return this;
 385 }
 386
 387 CYFunctionParameter *CYIfComprehension::Parameter(CYContext &context) const {
 388     return NULL;
 389 }
 390
 391 CYStatement *CYIfComprehension::Replace(CYContext &context, CYStatement *statement) const {
 392     return $ CYIf(test_, CYComprehension::Replace(context, statement));
 393 }
 394
 395 CYExpression *CYIndirect::Replace(CYContext &context) {
 396     CYPrefix::Replace(context);
 397     return $M(rhs_, $S("$cyi"));
 398 }
 399
 400 CYExpression *CYIndirectMember::Replace(CYContext &context) {
 401     Replace_(context);
 402     return $M($ CYIndirect(object_), property_);
 403 }
 404
 405 CYExpression *CYInfix::Replace(CYContext &context) {
 406     context.Replace(lhs_);
 407     context.Replace(rhs_);
 408     return this;
 409 }
 410
 411 CYStatement *CYLabel::Replace(CYContext &context) {
 412     context.Replace(statement_);
 413     return this;
 414 }
 415
 416 CYStatement *CYLet::Replace(CYContext &context) {
 417     return $ CYWith($ CYObject(declarations_->Property(context)), &code_);
 418 }
 419
 420 void CYMember::Replace_(CYContext &context) {
 421     context.Replace(object_);
 422     context.Replace(property_);
 423 }
 424
 425 CYExpression *CYNew::Replace(CYContext &context) {
 426     context.Replace(constructor_);
 427     arguments_->Replace(context);
 428     return this;
 429 }
 430
 431 CYNumber *CYNull::Number(CYContext &context) {
 432     return $D(0);
 433 }
 434
 435 CYString *CYNull::String(CYContext &context) {
 436     return $S("null");
 437 }
 438
 439 CYNumber *CYNumber::Number(CYContext &context) {
 440     return this;
 441 }
 442
 443 CYString *CYNumber::String(CYContext &context) {
 444     // XXX: there is a precise algorithm for this
 445     return $S(apr_psprintf(context.pool_, "%.17g", Value()));
 446 }
 447
 448 CYExpression *CYObject::Replace(CYContext &context) {
 449     properties_->Replace(context);
 450     return this;
 451 }
 452
 453 CYFunctionParameter *CYOptionalFunctionParameter::Replace(CYContext &context, CYBlock &code) {
 454     CYFunctionParameter *parameter($ CYFunctionParameter(name_, next_));
 455     parameter = parameter->Replace(context, code);
 456
 457     CYVariable *name($ CYVariable(name_));
 458     code.AddPrev($ CYIf($ CYIdentical($ CYTypeOf(name), $S("undefined")), $$->*
 459         $E($ CYAssign(name, initializer_))
 460     ));
 461
 462     return parameter;
 463 }
 464
 465 CYExpression *CYPostfix::Replace(CYContext &context) {
 466     context.Replace(lhs_);
 467     return this;
 468 }
 469
 470 CYExpression *CYPrefix::Replace(CYContext &context) {
 471     context.Replace(rhs_);
 472     return this;
 473 }
 474
 475 // XXX: this is evil evil black magic. don't ask, don't tell... don't believe!
 476 #define MappingSet "0etnirsoalfucdphmgyvbxTwSNECAFjDLkMOIBPqzRH$_WXUVGYKQJZ"
 477 //#define MappingSet "0abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$_"
 478
 479 namespace {
 480     struct IdentifierUsageLess :
 481         std::binary_function<CYIdentifier *, CYIdentifier *, bool>
 482     {
 483         _finline bool operator ()(CYIdentifier *lhs, CYIdentifier *rhs) const {
 484             if (lhs->usage_ != rhs->usage_)
 485                 return lhs->usage_ > rhs->usage_;
 486             return lhs < rhs;
 487         }
 488     };
 489
 490     typedef std::set<CYIdentifier *, IdentifierUsageLess> IdentifierUsages;
 491 }
 492
 493 void CYProgram::Replace(CYContext &context) {
 494     CYScope scope;
 495     scope.parent_ = context.scope_;
 496     context.scope_ = &scope;
 497     statements_ = statements_->ReplaceAll(context);
 498     context.scope_ = scope.parent_;
 499     scope.Scope(context, statements_);
 500
 501     size_t offset(0);
 502
 503     CYCStringSet external;
 504     for (CYIdentifierValueSet::const_iterator i(scope.identifiers_.begin()); i != scope.identifiers_.end(); ++i)
 505         external.insert((*i)->Word());
 506
 507     IdentifierUsages usages;
 508
 509     if (offset < context.rename_.size())
 510         for (CYIdentifier *i(context.rename_[offset].identifier_); i != NULL; i = i->next_)
 511              usages.insert(i);
 512
 513     // XXX: totalling the probable occurrences and sorting by them would improve the result
 514     for (CYIdentifierUsageVector::const_iterator i(context.rename_.begin()); i != context.rename_.end(); ++i, ++offset) {
 515         //std::cout << *i << ":" << (*i)->offset_ << std::endl;
 516
 517         const char *name;
 518
 519         if (context.options_.verbose_)
 520             name = apr_psprintf(context.pool_, "$%"APR_SIZE_T_FMT"", offset);
 521         else {
 522             char id[8];
 523             id[7] = '\0';
 524
 525           id:
 526             unsigned position(7), local(offset + 1);
 527
 528             do {
 529                 unsigned index(local % (sizeof(MappingSet) - 1));
 530                 local /= sizeof(MappingSet) - 1;
 531                 id[--position] = MappingSet[index];
 532             } while (local != 0);
 533
 534             if (external.find(id + position) != external.end()) {
 535                 ++offset;
 536                 goto id;
 537             }
 538
 539             name = apr_pstrmemdup(context.pool_, id + position, 7 - position);
 540             // XXX: at some point, this could become a keyword
 541         }
 542
 543         for (CYIdentifier *identifier(i->identifier_); identifier != NULL; identifier = identifier->next_)
 544             identifier->Set(name);
 545     }
 546 }
 547
 548 void CYProperty::Replace(CYContext &context) { $T()
 549     context.Replace(value_);
 550     next_->Replace(context);
 551 }
 552
 553 CYStatement *CYReturn::Replace(CYContext &context) {
 554     context.Replace(value_);
 555     return this;
 556 }
 557
 558 void CYScope::Declare(CYContext &context, CYIdentifier *identifier, CYIdentifierFlags flags) {
 559     internal_.insert(CYIdentifierAddressFlagsMap::value_type(identifier, flags));
 560 }
 561
 562 CYIdentifier *CYScope::Lookup(CYContext &context, CYIdentifier *identifier) {
 563     std::pair<CYIdentifierValueSet::iterator, bool> insert(identifiers_.insert(identifier));
 564     return *insert.first;
 565 }
 566
 567 void CYScope::Merge(CYContext &context, CYIdentifier *identifier) {
 568     std::pair<CYIdentifierValueSet::iterator, bool> insert(identifiers_.insert(identifier));
 569     if (!insert.second) {
 570         if ((*insert.first)->offset_ < identifier->offset_)
 571             (*insert.first)->offset_ = identifier->offset_;
 572         identifier->replace_ = *insert.first;
 573         (*insert.first)->usage_ += identifier->usage_ + 1;
 574     }
 575 }
 576
 577 namespace {
 578     struct IdentifierOffset {
 579         size_t offset_;
 580         CYIdentifierFlags flags_;
 581         size_t usage_;
 582         CYIdentifier *identifier_;
 583
 584         IdentifierOffset(CYIdentifier *identifier, CYIdentifierFlags flags) :
 585             offset_(identifier->offset_),
 586             flags_(flags),
 587             usage_(identifier->usage_),
 588             identifier_(identifier)
 589         {
 590         }
 591     };
 592
 593     struct IdentifierOffsetLess :
 594         std::binary_function<const IdentifierOffset &, const IdentifierOffset &, bool>
 595     {
 596         _finline bool operator ()(const IdentifierOffset &lhs, const IdentifierOffset &rhs) const {
 597             if (lhs.offset_ != rhs.offset_)
 598                 return lhs.offset_ < rhs.offset_;
 599             if (lhs.flags_ != rhs.flags_)
 600                 return lhs.flags_ < rhs.flags_;
 601             /*if (lhs.usage_ != rhs.usage_)
 602                 return lhs.usage_ < rhs.usage_;*/
 603             return lhs.identifier_ < rhs.identifier_;
 604         }
 605     };
 606
 607     typedef std::set<IdentifierOffset, IdentifierOffsetLess> IdentifierOffsets;
 608 }
 609
 610 void CYScope::Scope(CYContext &context, CYStatement *&statements) {
 611     if (parent_ == NULL)
 612         return;
 613
 614     CYDeclarations *last(NULL), *curr(NULL);
 615
 616     IdentifierOffsets offsets;
 617
 618     for (CYIdentifierAddressFlagsMap::const_iterator i(internal_.begin()); i != internal_.end(); ++i)
 619         if (i->second != CYIdentifierMagic)
 620             offsets.insert(IdentifierOffset(i->first, i->second));
 621
 622     size_t offset(0);
 623
 624     for (IdentifierOffsets::const_iterator i(offsets.begin()); i != offsets.end(); ++i) {
 625         if (i->flags_ == CYIdentifierVariable) {
 626             CYDeclarations *next($ CYDeclarations($ CYDeclaration(i->identifier_)));
 627             if (last == NULL)
 628                 last = next;
 629             if (curr != NULL)
 630                 curr->SetNext(next);
 631             curr = next;
 632         }
 633
 634         if (offset < i->offset_)
 635             offset = i->offset_;
 636         if (context.rename_.size() <= offset)
 637             context.rename_.resize(offset + 1);
 638
 639         CYIdentifierUsage &rename(context.rename_[offset++]);
 640         i->identifier_->SetNext(rename.identifier_);
 641         rename.identifier_ = i->identifier_;
 642         rename.usage_ += i->identifier_->usage_ + 1;
 643     }
 644
 645     if (last != NULL) {
 646         CYVar *var($ CYVar(last));
 647         var->SetNext(statements);
 648         statements = var;
 649     }
 650
 651     for (CYIdentifierValueSet::const_iterator i(identifiers_.begin()); i != identifiers_.end(); ++i)
 652         if (internal_.find(*i) == internal_.end()) {
 653             //std::cout << *i << '=' << offset << std::endl;
 654             if ((*i)->offset_ < offset)
 655                 (*i)->offset_ = offset;
 656             parent_->Merge(context, *i);
 657         }
 658 }
 659
 660 CYStatement *CYStatement::Collapse(CYContext &context) {
 661     return this;
 662 }
 663
 664 CYStatement *CYStatement::ReplaceAll(CYContext &context) { $T(NULL)
 665     CYStatement *replace(this);
 666     context.Replace(replace);
 667     replace->SetNext(next_->ReplaceAll(context));
 668     return replace->Collapse(context);
 669 }
 670
 671 CYString *CYString::Concat(CYContext &context, CYString *rhs) const {
 672     size_t size(size_ + rhs->size_);
 673     char *value(new(context.pool_) char[size + 1]);
 674     memcpy(value, value_, size_);
 675     memcpy(value + size_, rhs->value_, rhs->size_);
 676     value[size] = '\0';
 677     return $S(value, size);
 678 }
 679
 680 CYNumber *CYString::Number(CYContext &context) {
 681     // XXX: there is a precise algorithm for this
 682     return NULL;
 683 }
 684
 685 CYString *CYString::String(CYContext &context) {
 686     return this;
 687 }
 688
 689 CYStatement *CYSwitch::Replace(CYContext &context) {
 690     context.Replace(value_);
 691     clauses_->Replace(context);
 692     return this;
 693 }
 694
 695 CYExpression *CYThis::Replace(CYContext &context) {
 696     return this;
 697 }
 698
 699 namespace cy {
 700 namespace Syntax {
 701
 702 CYStatement *Throw::Replace(CYContext &context) {
 703     context.Replace(value_);
 704     return this;
 705 }
 706
 707 } }
 708
 709 CYExpression *CYTrivial::Replace(CYContext &context) {
 710     return this;
 711 }
 712
 713 CYNumber *CYTrue::Number(CYContext &context) {
 714     return $D(1);
 715 }
 716
 717 CYString *CYTrue::String(CYContext &context) {
 718     return $S("true");
 719 }
 720
 721 namespace cy {
 722 namespace Syntax {
 723
 724 CYStatement *Try::Replace(CYContext &context) {
 725     code_.Replace(context);
 726     catch_->Replace(context);
 727     finally_->Replace(context);
 728     return this;
 729 }
 730
 731 } }
 732
 733 CYStatement *CYVar::Replace(CYContext &context) {
 734     return $E(declarations_->Replace(context));
 735 }
 736
 737 CYExpression *CYVariable::Replace(CYContext &context) {
 738     name_ = name_->Replace(context);
 739     return this;
 740 }
 741
 742 CYStatement *CYWhile::Replace(CYContext &context) {
 743     context.Replace(test_);
 744     context.Replace(code_);
 745     return this;
 746 }
 747
 748 CYStatement *CYWith::Replace(CYContext &context) {
 749     context.Replace(scope_);
 750     context.Replace(code_);
 751     return this;
 752 }
 753
 754 CYExpression *CYWord::ClassName(CYContext &context, bool object) {
 755     CYString *name($S(this));
 756     if (object)
 757         return $C1($V("objc_getClass"), name);
 758     else
 759         return name;
 760 }