Package org.antlr.analysis
Class NFAState
java.lang.Object
org.antlr.analysis.State
org.antlr.analysis.NFAState
A state within an NFA. At most 2 transitions emanate from any NFA state.
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Field Summary
FieldsModifier and TypeFieldDescriptionAssociate this NFAState with the corresponding GrammarAST node from which this node was created.static final int
static final int
protected int
What's its decision number from 1..n?int
Subrules (...)* and (...)+ have more than one decision point in the NFA created for them.protected String
During debugging and for nondeterminism warnings, it's useful to know what relationship this node has to the original grammar.What rule do we live in?int
Jean Bovet needs in the GUI to know which state pairs correspond to the start/stop of a block.protected boolean
Is this state the sole target of an EOT transition?For o-A->o type NFA tranitions, record the label that leads to this state.static final int
static final int
Which NFA are we in?(package private) int
How many transitions; 0, 1, or 2 transitionsstatic final int
static final int
Fields inherited from class org.antlr.analysis.State
acceptState, INVALID_STATE_NUMBER, stateNumber
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
int
int
boolean
boolean
void
setDecisionASTNode
(GrammarAST decisionASTNode) What AST node is associated with this NFAState? When you set the AST node, I set the node to point back to this NFA state.void
setDecisionNumber
(int decisionNumber) void
setDescription
(String description) void
setEOTTargetState
(boolean eot) void
Used during optimization to reset a state to have the (single) transition another state has.toString()
transition
(int i) int
translateDisplayAltToWalkAlt
(int displayAlt) The DFA decision for this NFA decision state always has an exit path for loops as n+1 for n alts in the loop.Methods inherited from class org.antlr.analysis.State
isAcceptState, setAcceptState
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Field Details
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LOOPBACK
public static final int LOOPBACK- See Also:
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BLOCK_START
public static final int BLOCK_START- See Also:
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OPTIONAL_BLOCK_START
public static final int OPTIONAL_BLOCK_START- See Also:
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BYPASS
public static final int BYPASS- See Also:
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RIGHT_EDGE_OF_BLOCK
public static final int RIGHT_EDGE_OF_BLOCK- See Also:
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MAX_TRANSITIONS
public static final int MAX_TRANSITIONS- See Also:
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numTransitions
int numTransitionsHow many transitions; 0, 1, or 2 transitions -
transition
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incidentEdgeLabel
For o-A->o type NFA tranitions, record the label that leads to this state. Useful for creating rich error messages when we find insufficiently (with preds) covered states. -
nfa
Which NFA are we in? -
decisionNumber
protected int decisionNumberWhat's its decision number from 1..n? -
decisionStateType
public int decisionStateTypeSubrules (...)* and (...)+ have more than one decision point in the NFA created for them. They both have a loop-exit-or-stay-in decision node (the loop back node). They both have a normal alternative block decision node at the left edge. The (...)* is worse as it even has a bypass decision (2 alts: stay in or bypass) node at the extreme left edge. This is not how they get generated in code as a while-loop or whatever deals nicely with either. For error messages (where I need to print the nondeterministic alts) and for interpretation, I need to use the single DFA that is created (for efficiency) but interpret the results differently depending on which of the 2 or 3 decision states uses the DFA. For example, the DFA will always report alt n+1 as the exit branch for n real alts, so I need to translate that depending on the decision state. If decisionNumber>0 then this var tells you what kind of decision state it is. -
enclosingRule
What rule do we live in? -
description
During debugging and for nondeterminism warnings, it's useful to know what relationship this node has to the original grammar. For example, "start of alt 1 of rule a". -
associatedASTNode
Associate this NFAState with the corresponding GrammarAST node from which this node was created. This is useful not only for associating the eventual lookahead DFA with the associated Grammar position, but also for providing users with nondeterminism warnings. Mainly used by decision states to report line:col info. Could also be used to track line:col for elements such as token refs. -
EOTTargetState
protected boolean EOTTargetStateIs this state the sole target of an EOT transition? -
endOfBlockStateNumber
public int endOfBlockStateNumberJean Bovet needs in the GUI to know which state pairs correspond to the start/stop of a block.
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Constructor Details
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NFAState
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Method Details
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getNumberOfTransitions
public int getNumberOfTransitions()- Specified by:
getNumberOfTransitions
in classState
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addTransition
- Specified by:
addTransition
in classState
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setTransition0
Used during optimization to reset a state to have the (single) transition another state has. -
transition
- Specified by:
transition
in classState
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translateDisplayAltToWalkAlt
public int translateDisplayAltToWalkAlt(int displayAlt) The DFA decision for this NFA decision state always has an exit path for loops as n+1 for n alts in the loop. That is really useful for displaying nondeterministic alts and so on, but for walking the NFA to get a sequence of edge labels or for actually parsing, we need to get the real alt number. The real alt number for exiting a loop is always 1 as transition 0 points at the exit branch (we compute DFAs always for loops at the loopback state). For walking/parsing the loopback state: 1 2 3 display alt (for human consumption) 2 3 1 walk alt For walking the block start: 1 2 3 display alt 1 2 3 For walking the bypass state of a (...)* loop: 1 2 3 display alt 1 1 2 all block alts map to entering loop exit means take bypass Non loop EBNF do not need to be translated; they are ignored by this method as decisionStateType==0. Return same alt if we can't translate. -
setDecisionASTNode
What AST node is associated with this NFAState? When you set the AST node, I set the node to point back to this NFA state. -
getDescription
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setDescription
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getDecisionNumber
public int getDecisionNumber() -
setDecisionNumber
public void setDecisionNumber(int decisionNumber) -
isEOTTargetState
public boolean isEOTTargetState() -
setEOTTargetState
public void setEOTTargetState(boolean eot) -
isDecisionState
public boolean isDecisionState() -
toString
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