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Remove the RuleContext.hashCode, equals, conflictsWith, and suffix methods since they produce unexpected behavior for ParserRuleContext and are no longer used for adaptivePredict

This commit is contained in:
Sam Harwell 2012-11-26 02:24:16 -06:00
parent 27cb0e4012
commit 6421e312a4
1 changed files with 0 additions and 115 deletions
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115
runtime/Java/src/org/antlr/v4/runtime/RuleContext.java
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@ -73,33 +73,12 @@ public class RuleContext implements RuleNode {
*/ */
public int invokingState = -1; public int invokingState = -1;
/** Computing the hashCode is very expensive and closureBusy()
* uses it to track when it's seen a state|ctx before to avoid
* infinite loops. As we add new contexts, record the hash code
* as this.invokingState + parent.cachedHashCode. Avoids walking
* up the tree for every hashCode(). Note that this caching works
* because a context is a monotonically growing tree of context nodes
* and nothing on the stack is ever modified...ctx just grows
* or shrinks.
*/
protected int cachedHashCode;
public RuleContext() {} public RuleContext() {}
public RuleContext(RuleContext parent, int invokingState) { public RuleContext(RuleContext parent, int invokingState) {
this.parent = parent; this.parent = parent;
//if ( parent!=null ) System.out.println("invoke "+stateNumber+" from "+parent); //if ( parent!=null ) System.out.println("invoke "+stateNumber+" from "+parent);
this.invokingState = invokingState; this.invokingState = invokingState;
this.cachedHashCode = invokingState;
if ( parent!=null ) {
this.cachedHashCode += parent.cachedHashCode;
}
}
@Override
public int hashCode() {
return cachedHashCode; // works with tests; don't recompute.
} }
public int depth() { public int depth() {
@ -112,100 +91,6 @@ public class RuleContext implements RuleNode {
return n; return n;
} }
/** Two contexts are equals() if both have
* same call stack; walk upwards to the root.
* Note that you may be comparing contexts in different alt trees.
*
* The hashCode is cheap as it's computed once upon each context
* push on the stack. Using it to make equals() more efficient.
*/
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
} else if (!(o instanceof RuleContext)) {
return false;
}
RuleContext other = (RuleContext)o;
if ( this.hashCode() != other.hashCode() ) {
return false; // can't be same if hash is different
}
// System.out.println("comparing "+this+" with "+other);
RuleContext sp = this;
while ( sp!=null && other!=null ) {
if ( sp == other ) return true;
if ( sp.invokingState != other.invokingState) return false;
sp = sp.parent;
other = other.parent;
}
if ( !(sp==null && other==null) ) {
return false; // both pointers must be at their roots after walk
}
return true;
}
/** Two contexts conflict() if they are equals() or one is a stack suffix
* of the other. For example, contexts [21 12 $] and [21 9 $] do not
* conflict, but [21 $] and [21 12 $] do conflict. Note that I should
* probably not show the $ in this case. There is a dummy node for each
* stack that just means empty; $ is a marker that's all.
*
* This is used in relation to checking conflicts associated with a
* single NFA state's configurations within a single DFA state.
* If there are configurations s and t within a DFA state such that
* s.state=t.state && s.alt != t.alt && s.ctx conflicts t.ctx then
* the DFA state predicts more than a single alt--it's nondeterministic.
* Two contexts conflict if they are the same or if one is a suffix
* of the other.
*
* When comparing contexts, if one context has a stack and the other
* does not then they should be considered the same context. The only
* way for an NFA state p to have an empty context and a nonempty context
* is the case when closure falls off end of rule without a call stack
* and re-enters the rule with a context. This resolves the issue I
* discussed with Sriram Srinivasan Feb 28, 2005 about not terminating
* fast enough upon nondeterminism.
*/
public boolean conflictsWith(RuleContext other) {
return this.suffix(other) || this.equals(other);
}
/** [$] suffix any context
* [21 $] suffix [21 12 $]
* [21 12 $] suffix [21 $]
* [21 18 $] suffix [21 18 12 9 $]
* [21 18 12 9 $] suffix [21 18 $]
* [21 12 $] not suffix [21 9 $]
*
* Example "[21 $] suffix [21 12 $]" means: rule r invoked current rule
* from state 21. Rule s invoked rule r from state 12 which then invoked
* current rule also via state 21. While the context prior to state 21
* is different, the fact that both contexts emanate from state 21 implies
* that they are now going to track perfectly together. Once they
* converged on state 21, there is no way they can separate. In other
* words, the prior stack state is not consulted when computing where to
* go in the closure operation. x$ and xy$ are considered the same stack.
* If x is popped off then $ and y$ remain; they are now an empty and
* nonempty context comparison. So, if one stack is a suffix of
* another, then it will still degenerate to the simple empty stack
* comparison case.
*/
protected boolean suffix(RuleContext other) {
RuleContext sp = this;
// if one of the contexts is empty, it never enters loop and returns true
while ( sp.parent!=null && other.parent!=null ) {
if ( sp.invokingState != other.invokingState ) {
return false;
}
sp = sp.parent;
other = other.parent;
}
//System.out.println("suffix");
return true;
}
/** A context is empty if there is no invoking state; meaning nobody call /** A context is empty if there is no invoking state; meaning nobody call
* current context. * current context.
*/ */