# # Copyright (c) 2012-2017 The ANTLR Project. All rights reserved. # Use of this file is governed by the BSD 3-clause license that # can be found in the LICENSE.txt file in the project root. # # The following images show the relation of states and # {@link ATNState#transitions} for various grammar constructs. # # # #

Basic Blocks

# #

Rule

# # # #

Block of 1 or more alternatives

# # # #

Greedy Loops

# #

Greedy Closure: {@code (...)*}

# # # #

Greedy Positive Closure: {@code (...)+}

# # # #

Greedy Optional: {@code (...)?}

# # # #

Non-Greedy Loops

# #

Non-Greedy Closure: {@code (...)*?}

# # # #

Non-Greedy Positive Closure: {@code (...)+?}

# # # #

Non-Greedy Optional: {@code (...)??}

# # # from antlr4.atn.Transition import Transition INITIAL_NUM_TRANSITIONS = 4 class ATNState(object): # constants for serialization INVALID_TYPE = 0 BASIC = 1 RULE_START = 2 BLOCK_START = 3 PLUS_BLOCK_START = 4 STAR_BLOCK_START = 5 TOKEN_START = 6 RULE_STOP = 7 BLOCK_END = 8 STAR_LOOP_BACK = 9 STAR_LOOP_ENTRY = 10 PLUS_LOOP_BACK = 11 LOOP_END = 12 serializationNames = [ "INVALID", "BASIC", "RULE_START", "BLOCK_START", "PLUS_BLOCK_START", "STAR_BLOCK_START", "TOKEN_START", "RULE_STOP", "BLOCK_END", "STAR_LOOP_BACK", "STAR_LOOP_ENTRY", "PLUS_LOOP_BACK", "LOOP_END" ] INVALID_STATE_NUMBER = -1 def __init__(self): # Which ATN are we in? self.atn = None self.stateNumber = ATNState.INVALID_STATE_NUMBER self.stateType = None self.ruleIndex = 0 # at runtime, we don't have Rule objects self.epsilonOnlyTransitions = False # Track the transitions emanating from this ATN state. self.transitions = [] # Used to cache lookahead during parsing, not used during construction self.nextTokenWithinRule = None def __hash__(self): return self.stateNumber def __eq__(self, other): return isinstance(other, ATNState) and self.stateNumber==other.stateNumber def onlyHasEpsilonTransitions(self): return self.epsilonOnlyTransitions def isNonGreedyExitState(self): return False def __str__(self): return str(self.stateNumber) def addTransition(self, trans:Transition, index:int=-1): if len(self.transitions)==0: self.epsilonOnlyTransitions = trans.isEpsilon elif self.epsilonOnlyTransitions != trans.isEpsilon: self.epsilonOnlyTransitions = False # TODO System.err.format(Locale.getDefault(), "ATN state %d has both epsilon and non-epsilon transitions.\n", stateNumber); if index==-1: self.transitions.append(trans) else: self.transitions.insert(index, trans) class BasicState(ATNState): def __init__(self): super().__init__() self.stateType = self.BASIC class DecisionState(ATNState): def __init__(self): super().__init__() self.decision = -1 self.nonGreedy = False # The start of a regular {@code (...)} block. class BlockStartState(DecisionState): def __init__(self): super().__init__() self.endState = None class BasicBlockStartState(BlockStartState): def __init__(self): super().__init__() self.stateType = self.BLOCK_START # Terminal node of a simple {@code (a|b|c)} block. class BlockEndState(ATNState): def __init__(self): super().__init__() self.stateType = self.BLOCK_END self.startState = None # The last node in the ATN for a rule, unless that rule is the start symbol. # In that case, there is one transition to EOF. Later, we might encode # references to all calls to this rule to compute FOLLOW sets for # error handling. # class RuleStopState(ATNState): def __init__(self): super().__init__() self.stateType = self.RULE_STOP class RuleStartState(ATNState): def __init__(self): super().__init__() self.stateType = self.RULE_START self.stopState = None self.isPrecedenceRule = False # Decision state for {@code A+} and {@code (A|B)+}. It has two transitions: # one to the loop back to start of the block and one to exit. # class PlusLoopbackState(DecisionState): def __init__(self): super().__init__() self.stateType = self.PLUS_LOOP_BACK # Start of {@code (A|B|...)+} loop. Technically a decision state, but # we don't use for code generation; somebody might need it, so I'm defining # it for completeness. In reality, the {@link PlusLoopbackState} node is the # real decision-making note for {@code A+}. # class PlusBlockStartState(BlockStartState): def __init__(self): super().__init__() self.stateType = self.PLUS_BLOCK_START self.loopBackState = None # The block that begins a closure loop. class StarBlockStartState(BlockStartState): def __init__(self): super().__init__() self.stateType = self.STAR_BLOCK_START class StarLoopbackState(ATNState): def __init__(self): super().__init__() self.stateType = self.STAR_LOOP_BACK class StarLoopEntryState(DecisionState): def __init__(self): super().__init__() self.stateType = self.STAR_LOOP_ENTRY self.loopBackState = None # Indicates whether this state can benefit from a precedence DFA during SLL decision making. self.isPrecedenceDecision = None # Mark the end of a * or + loop. class LoopEndState(ATNState): def __init__(self): super().__init__() self.stateType = self.LOOP_END self.loopBackState = None # The Tokens rule start state linking to each lexer rule start state */ class TokensStartState(DecisionState): def __init__(self): super().__init__() self.stateType = self.TOKEN_START