/interpreter/tags/at2dist220411/src/edu/vub/at/objects/natives/grammar/AGBegin.java

http://ambienttalk.googlecode.com/ · Java · 142 lines · 72 code · 16 blank · 54 comment · 6 complexity · 3c61c4fdb6dde5cc0f218304cf781db3 MD5 · raw file

  1. /**
  2. * AmbientTalk/2 Project
  3. * AGBegin.java created on 26-jul-2006 at 12:26:48
  4. * (c) Programming Technology Lab, 2006 - 2007
  5. * Authors: Tom Van Cutsem & Stijn Mostinckx
  6. *
  7. * Permission is hereby granted, free of charge, to any person
  8. * obtaining a copy of this software and associated documentation
  9. * files (the "Software"), to deal in the Software without
  10. * restriction, including without limitation the rights to use,
  11. * copy, modify, merge, publish, distribute, sublicense, and/or
  12. * sell copies of the Software, and to permit persons to whom the
  13. * Software is furnished to do so, subject to the following
  14. * conditions:
  15. *
  16. * The above copyright notice and this permission notice shall be
  17. * included in all copies or substantial portions of the Software.
  18. *
  19. * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  20. * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  21. * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  22. * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  23. * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  24. * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  25. * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  26. * OTHER DEALINGS IN THE SOFTWARE.
  27. */
  28. package edu.vub.at.objects.natives.grammar;
  29. import edu.vub.at.eval.Evaluator;
  30. import edu.vub.at.exceptions.InterpreterException;
  31. import edu.vub.at.exceptions.XTypeMismatch;
  32. import edu.vub.at.objects.ATAbstractGrammar;
  33. import edu.vub.at.objects.ATContext;
  34. import edu.vub.at.objects.ATObject;
  35. import edu.vub.at.objects.ATTable;
  36. import edu.vub.at.objects.grammar.ATBegin;
  37. import edu.vub.at.objects.grammar.ATStatement;
  38. import edu.vub.at.objects.mirrors.NativeClosure;
  39. import edu.vub.at.objects.natives.NATNumber;
  40. import edu.vub.at.objects.natives.NATText;
  41. import edu.vub.util.TempFieldGenerator;
  42. import java.util.HashMap;
  43. import java.util.HashSet;
  44. import java.util.Set;
  45. /**
  46. * AGBegin represents the abstract grammar element of a list of statements.
  47. * Examples:
  48. * <tt>a ; b ; c</tt>
  49. *
  50. * @author tvcutsem
  51. */
  52. public final class AGBegin extends NATAbstractGrammar implements ATBegin {
  53. private final ATTable statements_;
  54. // contains a cached version of the expression's free variables
  55. private Set freeVars_;
  56. public AGBegin(ATTable statements) {
  57. statements_ = statements;
  58. }
  59. /**
  60. * AGBEGIN encapsulates a sequence of statements and evaluates each of these statements in turn.
  61. * The return value is the value of the last statement.
  62. *
  63. * AGBEGIN([statement | statements]).eval(ctx) = statement.eval(ctx) ; BEGIN(statements).eval(ctx)
  64. * AGBEGIN([statement]).eval(ctx) = statement.eval(ctx)
  65. * AGBEGIN([]).eval(ctx) = nil
  66. *
  67. * Note that this implementation of begin is *not* tail-recursive.
  68. * Tail-recursion is made impossible because Java will not allow a return
  69. * to the caller until the last expression is also evaluated. Tail-recursion optimalisation
  70. * requires a minimal form of explicit continuations.
  71. */
  72. public ATObject meta_eval(ATContext ctx) throws InterpreterException {
  73. NATNumber siz = statements_.base_length().asNativeNumber();
  74. int lastIdx = siz.javaValue;
  75. if (lastIdx == 0) {
  76. return Evaluator.getNil();
  77. }
  78. for (int i = 1; i < lastIdx; i++) {
  79. statements_.base_at(NATNumber.atValue(i)).meta_eval(ctx);
  80. }
  81. return statements_.base_at(NATNumber.atValue(lastIdx)).meta_eval(ctx);
  82. }
  83. /**
  84. * AGBEGIN(statements*).quote(ctx) = AGBEGIN((statements*).quote(ctx))
  85. */
  86. public ATObject meta_quote(ATContext ctx) throws InterpreterException {
  87. return new AGBegin(statements_.meta_quote(ctx).asTable());
  88. }
  89. public ATTable base_statements() { return statements_; }
  90. public NATText meta_print() throws InterpreterException {
  91. return Evaluator.printAsStatements(statements_);
  92. }
  93. public NATText impl_asUnquotedCode(TempFieldGenerator objectMap) throws InterpreterException {
  94. objectMap.incQuoteLevel();
  95. NATText code = Evaluator.codeAsStatements(objectMap, statements_);
  96. objectMap.decQuoteLevel();
  97. return NATText.atValue("{" + code.javaValue + "}");
  98. }
  99. public ATBegin asBegin() throws XTypeMismatch {
  100. return this;
  101. }
  102. /**
  103. * FV({ stmt1; stmt2; ... }) = FV(stmt1) U FV(stmt2) U ... \ (IV(stmt1) U IV(stmt2) U ...) }
  104. */
  105. public Set impl_freeVariables() throws InterpreterException {
  106. if (freeVars_ == null) {
  107. freeVars_ = new HashSet();
  108. final Set boundVars = new HashSet();
  109. statements_.base_each_(new NativeClosure(this) {
  110. public ATObject base_apply(ATTable args) throws InterpreterException {
  111. ATAbstractGrammar stmt = this.get(args, 1).asAbstractGrammar();
  112. freeVars_.addAll(stmt.impl_freeVariables());
  113. if (stmt.isDefinition()) {
  114. boundVars.addAll(stmt.asDefinition().impl_introducedVariables());
  115. }
  116. return stmt;
  117. }
  118. });
  119. freeVars_.removeAll(boundVars);
  120. }
  121. return freeVars_;
  122. }
  123. public Set impl_quotedFreeVariables() throws InterpreterException {
  124. return statements_.impl_quotedFreeVariables();
  125. }
  126. }