org.antlr.analysis
Class NFAConfiguration

java.lang.Object
  extended by org.antlr.analysis.NFAConfiguration

public class NFAConfiguration
extends java.lang.Object

An NFA state, predicted alt, and syntactic/semantic context. The syntactic context is a pointer into the rule invocation chain used to arrive at the state. The semantic context is the unordered set semantic predicates encountered before reaching an NFA state.


Field Summary
 int alt
          What alt is predicted by this configuration
 NFAContext context
          What is the stack of rule invocations that got us to state?
protected  int numberEpsilonTransitionsEmanatingFromState
          Lots of NFA states have only epsilon edges (1 or 2).
protected  boolean resolved
          Indicate that this configuration has been resolved and no further DFA processing should occur with it.
protected  boolean resolveWithPredicate
          This bit is used to indicate a semantic predicate will be used to resolve the conflict.
 SemanticContext semanticContext
          The set of semantic predicates associated with this NFA configuration.
protected  boolean singleAtomTransitionEmanating
          Indicates that the NFA state associated with this configuration has exactly one transition and it's an atom (not epsilon etc...).
 int state
          The NFA state associated with this configuration
 
Constructor Summary
NFAConfiguration(int state, int alt, NFAContext context, SemanticContext semanticContext)
           
 
Method Summary
 boolean equals(java.lang.Object o)
          An NFA configuration is equal to another if both have the same state, the predict the same alternative, and syntactic/semantic contexts are the same.
 int hashCode()
           
 java.lang.String toString()
           
 java.lang.String toString(boolean showAlt)
           
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

state

public int state
The NFA state associated with this configuration


alt

public int alt
What alt is predicted by this configuration


context

public NFAContext context
What is the stack of rule invocations that got us to state?


semanticContext

public SemanticContext semanticContext
The set of semantic predicates associated with this NFA configuration. The predicates were found on the way to the associated NFA state in this syntactic context. Set: track nodes in grammar containing the predicate for error messages and such (nice to know where the predicate came from in case of duplicates etc...). By using a set, the equals() method will correctly show {pred1,pred2} as equals() to {pred2,pred1}.


resolved

protected boolean resolved
Indicate that this configuration has been resolved and no further DFA processing should occur with it. Essentially, this is used as an "ignore" bit so that upon a set of nondeterministic configurations such as (s|2) and (s|3), I can set (s|3) to resolved=true (and any other configuration associated with alt 3).


resolveWithPredicate

protected boolean resolveWithPredicate
This bit is used to indicate a semantic predicate will be used to resolve the conflict. Method DFA.findNewDFAStatesAndAddDFATransitions will add edges for the predicates after it performs the reach operation. The nondeterminism resolver sets this when it finds a set of nondeterministic configurations (as it does for "resolved" field) that have enough predicates to resolve the conflit.


numberEpsilonTransitionsEmanatingFromState

protected int numberEpsilonTransitionsEmanatingFromState
Lots of NFA states have only epsilon edges (1 or 2). We can safely consider only n>0 during closure.


singleAtomTransitionEmanating

protected boolean singleAtomTransitionEmanating
Indicates that the NFA state associated with this configuration has exactly one transition and it's an atom (not epsilon etc...).

Constructor Detail

NFAConfiguration

public NFAConfiguration(int state,
                        int alt,
                        NFAContext context,
                        SemanticContext semanticContext)
Method Detail

equals

public boolean equals(java.lang.Object o)
An NFA configuration is equal to another if both have the same state, the predict the same alternative, and syntactic/semantic contexts are the same. I don't think the state|alt|ctx could be the same and have two different semantic contexts, but might as well define equals to be everything.

Overrides:
equals in class java.lang.Object

hashCode

public int hashCode()
Overrides:
hashCode in class java.lang.Object

toString

public java.lang.String toString()
Overrides:
toString in class java.lang.Object

toString

public java.lang.String toString(boolean showAlt)


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