Examples of wyautl.core.Automaton

wyautl.core.Automaton
type term Bool // bool type term Int // int type term Not(Type) // negation type term Or{Type...} // union of zero or more types term And{Type...} // intersection of zero or more types define Type as Void | Bool | Int | Not | Or | And
In this simple language, we can express types such as the following:
- Not(Or{Int,Bool}) --- the set of values excluding the integers and booleans
- And{Int,Bool} --- the set of values in both the integers and booleans (i.e. the empty set).
We can also see how the various components correspond to states in an automaton. Consider the following examples:
- Not(Void) --- this corresponds to an automaton with two states: 1) a term with no child representing Void; 2) a term representing Not which has a single child referring to state 1.
- Or{Int,Bool} --- corresponds to an automaton with four states: 1) a term with no child representing Int; 2) a term with no child representing Bool; 3) a set with two children referring to states 1 and 2; 4) a term representing Or with a single child referring to state 3.
Notes
- Roots. States can be explicitly marked as roots to provide a way to track them through the various operations that might be performed on an automaton. In particular, as states are rewritten, the roots will be updated accordingly.
- Minimisation. An automaton which has the strong equivalence property is said to be minimised. Automata are generally kept in the minimised form, and only use of the set() method can break this. The strong equivalence property guarantees that there are no two distinct, but equivalent states. In order to restore this property, the minimise() function must be called explicitly.
  
  Compaction. An automaton which does not contain garbage states is said to be compacted. Automata are generally kept in compacted form, and only use of the set() method can break this. Garbage states are those not reachable from any marked root state. In order to restore this property, the compact() function must be called explicitly.
- Canonical Form. An automaton which is minimised is not guaranteed to be canonical. This means we can have automata which are effectively equivalent, but which not considered identical (i.e., where equals() returns false). In some circumstance, it is desirable to move an automaton into canonical form, and this can be achieved with the canonicalise() function.
- Virtual States. In the internal representation of automata, leaf states may be not be represented as actual states. This will occur if the leaf node does not include any supplementary data, and is primarily for space and performance optimisation. In such case, the node is represented as a child node using a negative index.
@author David J. Pearce


    return type;
  }


  protected Type expandAsType(Type type, HashMap<String, Type> macros) {
    Automaton automaton = type.automaton();
    HashMap<String, Integer> roots = new HashMap<String, Integer>();
    HashMap<Integer,Integer> visited = new HashMap<Integer,Integer>();


    ArrayList<Automaton.State> states = new ArrayList<Automaton.State>();
    for(int i=0;i!=automaton.nStates();++i) {
      states.add(automaton.get(i).clone());
    }
    int root = expand(automaton.getRoot(0), states, visited,
        roots, macros);
    automaton = new Automaton(states.toArray(new Automaton.State[states.size()]));
    automaton.setRoot(0, root);
    return Type.construct(automaton);
  }

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            } else {
              // In this, we have a term which is specified to
              // have an argument, but for which no argument is
              // given. In which case, we simply expand the term
              // to include its default argument type.
              Automaton macro_automaton = macro.automaton();
              int root = Automata.extract(macro_automaton, macro_automaton.getRoot(0), states);
              // We store the location of the expanded macro into the
              // roots cache so that it can be reused if/when we
              // encounter the same macro again.
              roots.put(name, root);
              visited.put(node, root);
              return expand(root, states, visited, roots, macros);
            }
          } else if (macro != null && !(macro instanceof Type.Term)) {
            // In this case, we have identified a nominal type which
            // should be inlined into this automaton and then
            // recursively expanded as necessary.
            Automaton macro_automaton = macro.automaton();
            int element =  Automata.extract(macro_automaton, macro_automaton.getRoot(0), states);
            int base = states.size();
            states.add(new Automaton.Strung(name));
            states.add(new Automaton.List(base, element));
            states.add(new Automaton.Term(K_Nominal,
                base+1));

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  private void readTypePool(int size) throws IOException {
    final SemanticType[] myTypePool = new SemanticType[size];
    BinaryAutomataReader reader = new BinaryAutomataReader(input,
        Types.SCHEMA);
    Automaton global = reader.read();


    for (int i = 0; i != size; ++i) {
      Automaton automaton = new Automaton();
      int root = automaton.addAll(global.getRoot(i), global);
      automaton.setRoot(0, root);
      SemanticType t = SemanticType.construct(automaton);
      myTypePool[i] = t;
    }


    typePool = myTypePool;

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    myOut();
  }


  private void writeSchema(Type.Term tt) {
    Automaton automaton = tt.automaton();
    BitSet visited = new BitSet(automaton.nStates());
    writeSchema(automaton.getRoot(0), automaton, visited);
  }

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  }


  private void writeTypePool(BinaryOutputStream output) throws IOException {
    // First, we accumulate the automata for all types in the pool into one
    // automaton. This helps reduce the amount of redundancy between types.
    Automaton global = new Automaton();
    for (int i = 0; i != typePool.size(); ++i) {
      Automaton automaton = typePool.get(i).automaton();
      int root = global.addAll(automaton.getRoot(0), automaton);
      global.setRoot(i, root);
    }


    global.minimise();
    global.compact();

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        // this is basically a hack to allow reading in wyone files so
        // we can debug them.
        try {
          FileInputStream fin = new FileInputStream(args.get(0));
          PrettyAutomataReader reader = new PrettyAutomataReader(fin,SCHEMA);
          Automaton automaton = reader.read();


          new PrettyAutomataWriter(System.err, SCHEMA, "And",
              "Or").write(automaton);
          IterativeRewriter.Strategy<InferenceRule> inferenceStrategy = new UnfairStateRuleRewriteStrategy<InferenceRule>(
              automaton, Solver.inferences, Solver.SCHEMA);

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    }


  private static void reduce(String text, RewriteMode rwMode) {
    try {
      Parser parser = new Parser(text);
      Automaton automaton = new Automaton();
      int root = parser.parse(automaton);
      automaton.setRoot(0, root);


      PrettyAutomataWriter writer = new PrettyAutomataWriter(System.out,
          Arithmetic.SCHEMA, "Or", "And");
      System.out.println("------------------------------------");
      writer.write(automaton);

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    }


    private static void reduce(String text, RewriteMode rwMode) {
  try {
      Parser parser = new Parser(text);
      Automaton automaton = new Automaton();
      int root = parser.parse(automaton);
      automaton.setRoot(0, root);


      PrettyAutomataWriter writer = new PrettyAutomataWriter(System.out,
                   Quantifiers.SCHEMA, "Or", "And");
      System.out.println("------------------------------------");
      writer.write(automaton);

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   * @param type
   * @return the minimal size, or Integer.MAX_VALUE (to signal infinity ---
   *         which *should* be impossible).
   */
  public static int minimumSize(Type type) {
    Automaton automaton = type.automaton();
    automaton.compact();
    automaton.minimise();
    BitSet onStack = new BitSet();
    int size = minimumSize(automaton.getRoot(0), onStack, automaton);
    if(size < 0) {
      throw new RuntimeException("PROBLEM --- " + type);
    }
    return size;
  }

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    }


    private static void reduce(String text, RewriteMode rwMode) {
  try {
      Parser parser = new Parser(text);
      Automaton automaton = new Automaton();
      int root = parser.parse(automaton);
      automaton.setRoot(0, root);


      PrettyAutomataWriter writer = new PrettyAutomataWriter(System.out,
                   Closure.SCHEMA, "Or", "And");
      System.out.println("------------------------------------");
      writer.write(automaton);

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Examples of wyautl.core.Automaton

Notes

Related Classes of wyautl.core.Automaton