Class ATNConfig

  • Direct Known Subclasses:

    public class ATNConfig
    extends Object
    A tuple: (ATN state, predicted alt, syntactic, semantic context). The syntactic context is a graph-structured stack node whose path(s) to the root is the rule invocation(s) chain used to arrive at the state. The semantic context is the tree of semantic predicates encountered before reaching an ATN state.
    • Field Detail

      • state

        public final ATNState state
        The ATN state associated with this configuration
      • alt

        public final int alt
        What alt (or lexer rule) is predicted by this configuration
      • context

        public PredictionContext context
        The stack of invoking states leading to the rule/states associated with this config. We track only those contexts pushed during execution of the ATN simulator.
      • reachesIntoOuterContext

        public int reachesIntoOuterContext
        We cannot execute predicates dependent upon local context unless we know for sure we are in the correct context. Because there is no way to do this efficiently, we simply cannot evaluate dependent predicates unless we are in the rule that initially invokes the ATN simulator.

        closure() tracks the depth of how far we dip into the outer context: depth > 0. Note that it may not be totally accurate depth since I don't ever decrement. TODO: make it a boolean then

        For memory efficiency, the isPrecedenceFilterSuppressed() method is also backed by this field. Since the field is publicly accessible, the highest bit which would not cause the value to become negative is used to store this field. This choice minimizes the risk that code which only compares this value to 0 would be affected by the new purpose of the flag. It also ensures the performance of the existing ATNConfig constructors as well as certain operations like ATNConfigSet.add(ATNConfig, DoubleKeyMap) method are completely unaffected by the change.

    • Method Detail

      • isPrecedenceFilterSuppressed

        public final boolean isPrecedenceFilterSuppressed()
      • setPrecedenceFilterSuppressed

        public final void setPrecedenceFilterSuppressed​(boolean value)
      • equals

        public boolean equals​(Object o)
        An ATN configuration is equal to another if both have the same state, they predict the same alternative, and syntactic/semantic contexts are the same.
        equals in class Object
      • equals

        public boolean equals​(ATNConfig other)
      • hashCode

        public int hashCode()
        hashCode in class Object
      • toString

        public String toString​(Recognizer<?,​?> recog,
                               boolean showAlt)