Class: Antlr4::Runtime::ParserATNSimulator

Inherits:
ATNSimulator show all
Defined in:
lib/antlr4/runtime/parser_atn_simulator.rb

Direct Known Subclasses

ProfilingATNSimulator

Constant Summary collapse

TURN_OFF_LR_LOOP_ENTRY_BRANCH_OPT = 
get_safe_env('TURN_OFF_LR_LOOP_ENTRY_BRANCH_OPT')

Constants inherited from ATNSimulator

ATNSimulator::SERIALIZED_UUID, ATNSimulator::SERIALIZED_VERSION

Instance Attribute Summary collapse

Attributes inherited from ATNSimulator

#atn, #shared_context_cache

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from ATNSimulator

#cached_context, check_condition, deserialize, #edge_factory, #state_factory, to_int, to_int32, to_long, to_uuid

Constructor Details

#initialize(parser, atn, decision_to_dfa, shared_context_cache) ⇒ ParserATNSimulator

Returns a new instance of ParserATNSimulator.



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 17

def initialize(parser, atn, decision_to_dfa, shared_context_cache)
  super(atn, shared_context_cache)
  @parser = parser
  @decision_to_dfa = decision_to_dfa
  @mode = PredictionMode::LL
  @merge_cache = nil
  @_input = nil
  @_start_index = nil
  @_outer_context = nil
  @_dfa = nil

  @debug = false
  @debug_list_atn_decisions = false
  @dfa_debug = false
  @retry_debug = false
end

Instance Attribute Details

#debug ⇒ Object

Returns the value of attribute debug.



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 4

def debug
  @debug
end

#debug_list_atn_decisions ⇒ Object

Returns the value of attribute debug_list_atn_decisions.



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 5

def debug_list_atn_decisions
  @debug_list_atn_decisions
end

#dfa_debug ⇒ Object

Returns the value of attribute dfa_debug.



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 6

def dfa_debug
  @dfa_debug
end

#retry_debug ⇒ Object

Returns the value of attribute retry_debug.



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 7

def retry_debug
  @retry_debug
end

Class Method Details

.get_safe_env(env_name) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 9

def self.get_safe_env(env_name)
  ENV[env_name]
rescue StandardError
  nil
end

Instance Method Details

#action_transition(config, t) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 940

def action_transition(config, t)
  puts('ACTION edge ' << t.rule_index << ':' << t.action_index) if @debug
  c = ATNConfig.new
  c.atn_config3(config, t.target)
  c
end

#adaptive_predict(input, decision, outer_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 41

def adaptive_predict(input, decision, outer_ctx)
  if @debug || @debug_list_atn_decisions
    puts('adaptivePredict decision ' << decision.to_s << ' exec la(1)==' << lookahead_name(input) << ' line ' << input.lt(1).line.to_s << ':' << input.lt(1).char_position_in_line.to_s)
  end

  @_input = input
  @_start_index = input.index
  @_outer_context = outer_ctx
  dfa = @decision_to_dfa[decision]
  @_dfa = dfa

  m = input.mark
  index = @_start_index

  # Now we are certain to have a specific decision's DFA
  # But, do we still need an initial state?
  begin
    dfa.precedence_dfa? ? s0 = dfa.precedence_start_state(parser.precedence) : s0 = dfa.s0

    if s0.nil?
      outer_ctx = ParserRuleContext::EMPTY if outer_ctx.nil?
      if @debug || @debug_list_atn_decisions
        puts('predictATN decision ' << dfa.decision.to_s << ' exec la(1)==' << lookahead_name(input) << ', outer_ctx=' << outer_ctx.to_s_recog(@parser))
      end

      full_ctx = false
      s0_closure = compute_start_state(dfa.atn_start_state, ParserRuleContext::EMPTY, full_ctx)

      if dfa.precedence_dfa?
        dfa.s0.configs = s0_closure # not used for prediction but useful to know start configs anyway
        s0_closure = apply_precedence_filter(s0_closure)
        s0 = add_dfa_state(dfa, DFAState.new(s0_closure))
        dfa.precedence_start_state(@parser.precedence, s0)
      else
        s0 = add_dfa_state(dfa, DFAState.new(s0_closure))
        dfa.s0 = s0
      end
    end

    alt = exec_atn(dfa, s0, input, index, outer_ctx)
    if @debug
      puts('DFA after predictATN: ' << dfa.to_s2(@parser.get_vocabulary))
    end
    return alt
  ensure
    @merge_cache = nil # wack cache after each prediction
    @_dfa = nil
    input.seek(index)
    input.release(m)
  end
end

#add_dfa_edge(dfa, from, t, to) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1099

def add_dfa_edge(dfa, from, t, to)
  if @debug
    puts('EDGE ' << from.to_s << ' -> ' << to.to_s << ' upon ' << token_name(t))
  end

  return nil if to.nil?

  to = add_dfa_state(dfa, to) # used existing if possible not incoming
  return to if from.nil? || t < -1 || t > atn.max_token_type

  from.edges = [] if from.edges.nil?

  from.edges[t + 1] = to # connect

  if @debug
    puts("DFA=\n" << dfa.to_s2(!@parser.nil? ? @parser.get_vocabulary : VocabularyImpl.EMPTY_VOCABULARY))
  end

  to
end

#add_dfa_state(dfa, d) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1120

def add_dfa_state(dfa, d)
  return d if d == @@error

  existing = dfa.states[d]
  return existing unless existing.nil?

  d.state_number = dfa.states.size
  unless d.configs.readonly
    d.configs.optimize_configs(self)
    d.configs.readonly = true
  end
  dfa.states[d] = d
  puts('adding new DFA state: ' << d.to_s) if @debug
  d
end

#alt_that_finished_decision_entry_rule(configs) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 620

def alt_that_finished_decision_entry_rule(configs)
  alts = IntervalSet.new
  i = 0
  while i < configs.configs.length
    c = configs.configs[i]
    depth = c.outer_context_depth
    if depth > 0 || (c.state.is_a?(Antlr4::Runtime::RuleStopState) && c.context.empty_path?)
      alts.add(c.alt)
    end
    i += 1
  end
  return ATN::INVALID_ALT_NUMBER if alts.intervals.empty?

  alts.min_element
end

#apply_precedence_filter(configs) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 496

def apply_precedence_filter(configs)
  states_from_alt1 = Map.new
  config_set = ATNConfigSet.new(configs.full_ctx)
  i = 0
  while i < configs.length
    config = configs[i]
    if config.alt != 1
      i += 1
      next
    end

    updated_context = config.semantic_context.eval_precedence(@parser, @_outer_context)
    if updated_context.nil?
      # the configuration was eliminated
      i += 1
      next
    end

    states_from_alt1.put(config.state.state_number, config.context)
    if updated_context != config.semantic_context
      atncfg = ATNConfig.new
      atncfg.atn_config3(config, updated_context)
      config_set.add(atncfg, @merge_cache)
    else
      config_set.add(config, @merge_cache)
    end
    i += 1
  end

  i = 0
  while i < configs.length
    config = configs[i]
    if config.alt == 1
      # already handled
      i += 1
      next
    end

    unless config.precedence_filter_suppressed?

      context = states_from_alt1.get(config.state.state_number)
      if !context.nil? && context.eql?(config.context)
        # eliminated
        i += 1
        next
      end
    end

    config_set.add(config, @merge_cache)
    i += 1
  end

  config_set
end

#can_drop_loop_entry_edge_in_left_recursive_rule?(config) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 823

def can_drop_loop_entry_edge_in_left_recursive_rule?(config)
  return false if TURN_OFF_LR_LOOP_ENTRY_BRANCH_OPT

  p = config.state
  # First check to see if we are in StarLoopEntryState generated during
  # left-recursion elimination. For efficiency, also check if
  # the context has an empty stack case. If so, it would mean
  # global FOLLOW so we can't perform optimization
  if p.state_type != ATNState::STAR_LOOP_ENTRY || !p.is_precedence_pecision || # Are we the special loop entry/exit state?
      config.context.empty? || # If SLL wildcard
      config.context.empty_path?

    return false
  end

  # Require all return states to return back to the same rule
  # that p is in.
  num_ctxs = config.context.size
  i = 0
  while i < num_ctxs
    return_state = atn.states.get(config.context.get_return_state(i))
    return false if return_state.rule_index != p.rule_index

    i += 1
  end

  decision_start_state = p.transition(0).target
  block_end_state_num = decision_start_state.end_state.state_number
  block_end_state = atn.states.get(block_end_state_num)

  # Verify that the top of each stack context leads to loop entry/exit
  # state through epsilon edges and w/o leaving rule.
  i = 0
  while i < num_ctxs
    return_state_number = config.context.get_return_state(i)
    return_state = atn.states.get(return_state_number)
    # all states must have single outgoing epsilon edge
    if return_state.number_of_transitions != 1 || !return_state.transition(0).epsilon?

      return false
    end

    # Look for prefix op case like 'not expr', (' type ')' expr
    return_state_target = return_state.transition(0).target
    if return_state.state_type == BLOCK_END && return_state_target == p
      i += 1
      next
    end
    # Look for 'expr op expr' or case where expr's return state is block end
    # of (...)* internal block the block end points to loop back
    # which points to p but we don't need to check that
    if return_state == block_end_state
      i += 1
      next
    end
    # Look for ternary expr ? expr : expr. The return state points at block end,
    # which points at loop entry state
    if return_state_target == block_end_state
      i += 1
      next
    end
    # Look for complex prefix 'between expr and expr' case where 2nd expr's
    # return state points at block end state of (...)* internal block
    if return_state_target.state_type == BLOCK_END && return_state_target.number_of_transitions == 1 && return_state_target.transition(0).epsilon? && return_state_target.transition(0).target == p

      i += 1
      next
    end

    # anything else ain't conforming
    return false
  end

  true
end

#clear_dfa ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 34

def clear_dfa
  d = 0
  while d < @decision_to_dfa.length
    @decision_to_dfa[d] = DFA.new(atn.decision_state(d), d)
  end
end

#closure(config, configs, closure_busy, collect_predicates, full_ctx, treat_eof_as_epsilon) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 697

def closure(config, configs, closure_busy, collect_predicates, full_ctx, treat_eof_as_epsilon)
  initial_depth = 0
  closure_checking_stop_state(config, configs, closure_busy, collect_predicates, full_ctx, initial_depth, treat_eof_as_epsilon)
end

#closure_(config, configs, closure_busy, collect_predicates, full_ctx, depth, treat_eof_as_epsilon) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 757

def closure_(config, configs, closure_busy, collect_predicates, full_ctx, depth, treat_eof_as_epsilon)
  p = config.state
  # optimization
  unless p.only_has_epsilon_transitions
    configs.add(config, @merge_cache)
    # make sure to not return here, because EOF transitions can act as
    # both epsilon transitions and non-epsilon transitions.
    #            if ( debug ) puts("added config "+configs)
  end

  i = 0
  while i < p.number_of_transitions
    if i == 0 && can_drop_loop_entry_edge_in_left_recursive_rule?(config)
      i += 1
      next
    end

    t = p.transition(i)
    continue_collecting = !(t.is_a? ActionTransition) && collect_predicates
    c = epsilon_target(config, t, continue_collecting, depth == 0, full_ctx, treat_eof_as_epsilon)
    unless c.nil?
      new_depth = depth
      if config.state.is_a? RuleStopState
        # target fell off end of rule mark resulting c as having dipped into outer context
        # We can't get here if incoming config was rule stop and we had context
        # track how far we dip into outer context.  Might
        # come in handy and we avoid evaluating context dependent
        # preds if this is > 0.

        if !@_dfa.nil? && @_dfa.precedence_dfa?
          outermost_precedence_return = t.outermost_precedence_return
          if outermost_precedence_return == @_dfa.atn_start_state.rule_index
            c.precedence_filter_suppressed(true)
          end
        end

        c.reaches_into_outer_context += 1

        added = !closure_busy.add?(c).nil?
        unless added
          i += 1
          next
        end

        configs.dips_into_outer_context = true # TODO: can remove? only care when we add to set per middle of this method
        new_depth -= 1
        puts('dips into outer ctx: ' << c.to_s) if @debug
      else
        added = !closure_busy.add?(c).nil?
        if !t.epsilon? && !added
          i += 1
          next
        end

        if t.is_a? RuleTransition
          # latch when new_depth goes negative - once we step out of the entry context we can't return
          new_depth += 1 if new_depth >= 0
        end
      end

      closure_checking_stop_state(c, configs, closure_busy, continue_collecting, full_ctx, new_depth, treat_eof_as_epsilon)
    end
    i += 1
  end
end

#closure_checking_stop_state(config, configs, closure_busy, collect_predicates, full_ctx, depth, treat_eof_as_epsilon) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 702

def closure_checking_stop_state(config, configs, closure_busy, collect_predicates, full_ctx, depth, treat_eof_as_epsilon)
  puts('closure(' << config.to_s2(@parser, true) << ')') if @debug

  if config.state.is_a? RuleStopState
    # We hit rule end. If we have context info, use it
    # run thru all possible stack tops in ctx
    if !config.context.empty?
      i = 0
      while i < config.context.size
        if config.context.get_return_state(i) == PredictionContext::EMPTY_RETURN_STATE
          if full_ctx
            atncfg = ATNConfig.new
            atncfg.atn_config6(config, config.state, EmptyPredictionContext::EMPTY)
            configs.add(atncfg, @merge_cache)
            i += 1
            next
          else # we have no context info, just chase follow links (if greedy)
            if @debug
              puts('FALLING off rule ' << rule_name(config.state.rule_index))
            end
            closure_(config, configs, closure_busy, collect_predicates, full_ctx, depth, treat_eof_as_epsilon)
          end
          i += 1
          next
        end
        return_state = atn.states[config.context.get_return_state(i)]
        new_context = config.context.get_parent(i) # "pop" return state
        c = ATNConfig.new
        c.atn_config2(return_state, config.alt, new_context, config.semantic_context)
        # While we have context to pop back from, we may have
        # gotten that context AFTER having falling off a rule.
        # Make sure we track that we are now out of context.
        #
        # This assignment also propagates the
        # isPrecedenceFilterSuppressed() value to the new
        # configuration.
        c.reaches_into_outer_context = config.reaches_into_outer_context
        closure_checking_stop_state(c, configs, closure_busy, collect_predicates, full_ctx, depth - 1, treat_eof_as_epsilon)
        i += 1
      end
      return
    elsif full_ctx
      # reached end of start rule
      configs.add(config, @merge_cache)
      return
    else # else if we have no context info, just chase follow links (if greedy)
      if @debug
        puts('FALLING off rule ' << rule_name(config.state.rule_index))
      end
    end
  end

  closure_(config, configs, closure_busy, collect_predicates, full_ctx, depth, treat_eof_as_epsilon)
end

#compute_reach_set(closure, t, full_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 362

def compute_reach_set(closure, t, full_ctx)
  puts('in computeReachSet, starting closure: ' << closure.to_s) if @debug

  @merge_cache = DoubleKeyMap.new if @merge_cache.nil?

  intermediate = ATNConfigSet.new(full_ctx)

  skipped_stop_states = nil

  # First figure out where we can reach on input t
  i = 0
  while i < closure.configs.length
    c = closure.configs[i]
    puts('testing ' << token_name(t) << ' at ' << c.to_s) if @debug

    if c.state.is_a? RuleStopState
      if full_ctx || t == IntStream::EOF
        skipped_stop_states = [] if skipped_stop_states.nil?

        skipped_stop_states.push(c)
      end
      i += 1
      next
    end

    n = c.state.number_of_transitions
    ti = 0
    while ti < n
      trans = c.state.transition(ti)
      target = reachable_target(trans, t)
      unless target.nil?
        atncfg = ATNConfig.new
        atncfg.atn_config3(c, target)
        intermediate.add(atncfg, @merge_cache)
      end
      ti += 1
    end
    i += 1
  end

  # Now figure out where the reach operation can take us...

  reach = nil

  if skipped_stop_states.nil? && t != Token::EOF
    if intermediate.configs.size == 1
      # Don' t pursue the closure if there is just one state.
      # It can only have one alternative just add to result
      # Also don't pursue the closure if there is unique alternative
      # among the configurations.
      reach = intermediate
    elsif unique_alt(intermediate) != ATN::INVALID_ALT_NUMBER
      # Also don't pursue the closure if there is unique alternative
      # among the configurations.
      reach = intermediate
    end
  end

  if reach.nil?
    reach = ATNConfigSet.new(full_ctx)
    closure_busy = Set.new
    treat_eof_as_epsilon = t == Token::EOF
    i = 0
    while i < intermediate.configs.length
      c = intermediate.configs[i]
      closure(c, reach, closure_busy, false, full_ctx, treat_eof_as_epsilon)
      i += 1
    end
  end

  if t == IntStream::EOF
    reach = remove_all_configs_not_in_rule_stop_state(reach, reach == intermediate)
  end

  if !skipped_stop_states.nil? && (!full_ctx || !PredictionMode.has_config_in_rule_stop_state?(reach))
    i = 0
    while i < skipped_stop_states.length
      c = skipped_stop_states[i]
      reach.add(c, @merge_cache)
      i += 1
    end
  end

  return nil if reach.empty?
  reach
end

#compute_start_state(p, ctx, full_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 478

def compute_start_state(p, ctx, full_ctx)
  # always at least the implicit call to start rule
  initial_context = PredictionContextUtils.from_rule_context(@atn, ctx)
  configs = ATNConfigSet.new(full_ctx)

  i = 0
  while i < p.number_of_transitions
    target = p.transition(i).target
    c = ATNConfig.new
    c.atn_config1(target, i + 1, initial_context)
    closure_busy = Set.new
    closure(c, configs, closure_busy, true, full_ctx, false)
    i += 1
  end

  configs
end

#compute_target_state(dfa, prev_d, t) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 207

def compute_target_state(dfa, prev_d, t)
  reach = compute_reach_set(prev_d.configs, t, false)
  if reach.nil?
    add_dfa_edge(dfa, prev_d, t, @@error)
    return @@error
  end

  # create new target state we'll add to DFA after it's complete
  d = DFAState.new(reach)

  predicted_alt = unique_alt(reach)

  if @debug
    alt_sub_sets = PredictionMode.conflicting_alt_subsets(reach)
    alt_sub_sets_str = '['
    alt_sub_sets.each do |x|
      alt_sub_sets_str << x.to_s
    end
    alt_sub_sets_str << ']'
    puts('SLL alt_sub_sets=' << alt_sub_sets_str << ', configs=' << reach.to_s << ', predict=' << predicted_alt.to_s << ', allSubsetsConflict=' << PredictionMode.all_subsets_conflict?(alt_sub_sets).to_s << ', conflicting_alts=' << conflicting_alts(reach).to_s)
  end

  if predicted_alt != ATN::INVALID_ALT_NUMBER
    # NO CONFLICT, UNIQUELY PREDICTED ALT
    d.is_accept_state = true
    d.configs.unique_alt = predicted_alt
    d.prediction = predicted_alt
  elsif PredictionMode.has_sll_conflict_terminating_prediction(@mode, reach)
    # MORE THAN ONE VIABLE ALTERNATIVE
    d.configs.conflictingAlts = conflicting_alts(reach)
    d.requires_full_context = true
    # in SLL-only mode, we will stop at this state and return the minimum alt
    d.is_accept_state = true
    d.prediction = d.configs.conflictingAlts.next_set_bit(0)
  end

  if d.is_accept_state && d.configs.has_semantic_context
    predicate_dfa_state(d, atn.decision_state(dfa.decision))
    d.prediction = ATN::INVALID_ALT_NUMBER unless d.predicates.nil?
  end

  # all adds to dfa are done after we've created full D state
  add_dfa_edge(dfa, prev_d, t, d)
end

#conflicting_alts(configs) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1034

def conflicting_alts(configs)
  altsets = PredictionMode.conflicting_alt_subsets(configs)
  PredictionMode.get_alts1(altsets)
end

#conflicting_alts_or_unique_alt(configs) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1039

def conflicting_alts_or_unique_alt(configs)
  if configs.unique_alt != ATN::INVALID_ALT_NUMBER
    conflict_alts = new BitSet
    conflict_alts.set(configs.unique_alt)
  else
    conflict_alts = configs.conflictingAlts
  end
  conflict_alts
end

#dump_dead_end_configs(nvae) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1065

def dump_dead_end_configs(nvae)
  STDERR.puts('dead end configs: ')
  nvae.getDeadEndConfigs.each do |c|
    trans = 'no edges'
    if c.state.number_of_transitions > 0
      t = c.state.transition(0)
      if t.is_a? AtomTransition
        at = t
        trans = 'Atom ' << token_name(at.label)
      elsif t.is_a? SetTransition
        st = t
        nott = st.is_a? NotSetTransition
        trans = (nott ? '~' : '') << 'Set ' << st.set.to_s
      end
    end
    STDERR.puts(c.to_s(@parser, true) << ':' << trans)
  end
end

#epsilon_target(config, t, collect_predicates, in_context, full_ctx, treat_eof_as_epsilon) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 905

def epsilon_target(config, t, collect_predicates, in_context, full_ctx, treat_eof_as_epsilon)
  case t.serialization_type
  when Transition::RULE
    rule_transition(config, t)

  when Transition::PRECEDENCE
    precedence_transition(config, t, collect_predicates, in_context, full_ctx)

  when Transition::PREDICATE
    pred_transition(config, t, collect_predicates, in_context, full_ctx)

  when Transition::ACTION
    action_transition(config, t)

  when Transition::EPSILON
    c = ATNConfig.new
    c.atn_config3(config, t.target)
    c

  when Transition::ATOM, Transition::RANGE, Transition::SET
    # EOF transitions act like epsilon transitions after the first EOF
    # transition is traversed
    if treat_eof_as_epsilon
      if t.matches(Token::EOF, 0, 1)
        c = ATNConfig.new
        c.atn_config3(config, t.target)
        return c
      end
    end

    return nil

  end
end

#eval_semantic_context1(pred_predictions, outer_ctx, complete) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 661

def eval_semantic_context1(pred_predictions, outer_ctx, complete)
  predictions = BitSet.new
  i = 0
  while i < pred_predictions.length
    pair = pred_predictions[i]
    if pair.pred == SemanticContext::NONE
      predictions.set(pair.alt)
      break unless complete
      i += 1
      next
    end

    full_ctx = false # in dfa
    predicate_evaluation_result = eval_semantic_context(pair.pred, outer_ctx, pair.alt, full_ctx)
    if @debug || @dfa_debug
      puts('eval pred ' << pair << '=' << predicate_evaluation_result)
    end

    unless predicate_evaluation_result
      i += 1
      next
    end

    puts('PREDICT ' << pair.alt) if @debug || @dfa_debug
    predictions.set(pair.alt)
    break unless complete
    i += 1
  end

  predictions
end

#eval_semantic_context2(pred, parser_call_stack, _alt, _full_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 693

def eval_semantic_context2(pred, parser_call_stack, _alt, _full_ctx)
  pred.eval(parser, parser_call_stack)
end

#exec_atn(dfa, s0, input, start_index, outer_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 93

def exec_atn(dfa, s0, input, start_index, outer_ctx)
  if @debug || @debug_list_atn_decisions
    puts('execATN decision ' << dfa.decision.to_s << ' exec la(1)==' << lookahead_name(input) << ' line ' << input.lt(1).line.to_s << ':' << input.lt(1).char_position_in_line.to_s)
  end

  previous_d = s0

  puts('s0 = ' << s0.to_s) if @debug

  t = input.la(1)

  loop do # while more work
    d = existing_target_state(previous_d, t)
    d = compute_target_state(dfa, previous_d, t) if d.nil?

    if d == @@error
      # if any configs in previous dipped into outer context, that
      # means that input up to t actually finished entry rule
      # at least for SLL decision. Full LL doesn' t dip into outer
      # so don't need special case.
      # We will get an error no matter what so delay until after
      # decision better error message. Also, no reachable target
      # ATN states in SLL implies LL will also get nowhere.
      # If conflict in states that dip out, choose min since we
      # will get error no matter what.
      exc = NoViableAltException.new
      exc.recognizer = @parser
      exc.input = input
      exc.context = outer_ctx
      exc.start_token = input.get(start_index)
      exc.offending_token = input.lt(1)
      exc.dead_end_configs = previous_d.configs

      input.seek(start_index)
      alt = syn_valid_or_sem_invalid_alt_that_finished_decision_entry_rule(previous_d.configs, outer_ctx)
      return alt if alt != ATN::INVALID_ALT_NUMBER

      raise exc
    end

    if d.requires_full_context && @mode != PredictionMode::SLL
      # IF PREDS, MIGHT RESOLVE TO SINGLE ALT => SLL (or syntax error)
      conflicting_alts = d.configs.conflictingAlts
      unless d.predicates.nil?
        puts('DFA state has preds in DFA sim LL failover') if @debug
        conflict_index = input.index
        input.seek(start_index) if conflict_index != start_index

        conflicting_alts = eval_semantic_context(d.predicates, outer_ctx, true)
        if conflicting_alts.cardinality == 1
          puts('Full LL avoided') if debug
          return conflicting_alts.next_set_bit(0)
        end

        if conflict_index != start_index
          # restore the index so reporting the fallback to full
          # context occurs with the index at the correct spot
          input.seek(conflict_index)
        end
      end

      if @dfa_debug
        puts('ctx sensitive state ' << outer_ctx.to_s << ' in ' << d.to_s)
      end
      full_ctx = true
      s0_closure = compute_start_state(dfa.atn_start_state, outer_ctx, full_ctx)
      report_attempting_full_context(dfa, conflicting_alts, d.configs, start_index, input.index)
      alt = exec_atn_with_full_context(dfa, d, s0_closure, input, start_index, outer_ctx)
      return alt
    end

    if d.is_accept_state
      return d.prediction if d.predicates.nil?

      stop_index = input.index
      input.seek(start_index)
      alts = eval_semantic_context(d.predicates, outer_ctx, true)
      case alts.cardinality
      when 0
        exc = NoViableAltException.new
        exc.recognizer = @parser
        exc.input = input
        exc.context = outer_ctx
        exc.start_token = input.get(start_index)
        exc.offending_token = input.lt(1)
        exc.dead_end_configs = d.configs
        raise exc

      when 1
        return alts.next_set_bit(0)

      else # report ambiguity after predicate evaluation to make sure the correct
        # set of ambig alts is reported.
        report_ambiguity(dfa, d, start_index, stop_index, false, alts, d.configs)
        return alts.next_set_bit(0)
      end
    end

    previous_d = d

    if t != IntStream::EOF
      input.consume
      t = input.la(1)
    end
  end
end

#exec_atn_with_full_context(dfa, d, s0, input, start_index, outer_ctx) ⇒ Object

comes back with reach.uniqueAlt set to a valid alt



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 270

def exec_atn_with_full_context(dfa, d, s0, input, start_index, outer_ctx)
  if @debug || @debug_list_atn_decisions
    puts('execATNWithFullContext ' << s0.to_s)
  end
  full_ctx = true
  found_exact_ambig = false
  reach = nil
  previous = s0
  input.seek(start_index)
  t = input.la(1)
  predicted_alt = 0
  loop do # while more work
    reach = compute_reach_set(previous, t, full_ctx)
    if reach.nil?
      # if any configs in previous dipped into outer context, that
      # means that input up to t actually finished entry rule
      # at least for LL decision. Full LL doesn't dip into outer
      # so don't need special case.
      # We will get an error no matter what so delay until after
      # decision better error message. Also, no reachable target
      # ATN states in SLL implies LL will also get nowhere.
      # If conflict in states that dip out, choose min since we
      # will get error no matter what.

      input.seek(start_index)
      alt = syn_valid_or_sem_invalid_alt_that_finished_decision_entry_rule(previous, outer_ctx)
      return alt if alt != ATN::INVALID_ALT_NUMBER

      exc = NoViableAltException.new
      exc.recognizer = @parser
      exc.input = input
      exc.context = outer_ctx
      exc.start_token = input.get(start_index)
      exc.offending_token = input.lt(1)
      exc.dead_end_configs = previous.configs
      raise exc
    end

    alt_sub_sets = PredictionMode.conflicting_alt_subsets(reach)
    if @debug
      tmp = ''
      alt_sub_sets.each do |as|
        tmp << as.to_s
        tmp << ' '
      end
      puts('LL alt_sub_sets=' << tmp << ', predict=' << PredictionMode.unique_alt(alt_sub_sets).to_s << ', resolvesToJustOneViableAlt=' << PredictionMode.resolves_to_just_one_viable_alt?(alt_sub_sets).to_s)
    end

    #      puts("alt_sub_sets: "+alt_sub_sets)
    #      System.err.println("reach="+reach+", "+reach.conflicting_alts)
    reach.unique_alt = unique_alt(reach)
    # unique prediction?
    if reach.unique_alt != ATN::INVALID_ALT_NUMBER
      predicted_alt = reach.unique_alt
      break
    end
    if @mode != PredictionMode::LL_EXACT_AMBIG_DETECTION
      predicted_alt = PredictionMode.resolves_to_just_one_viable_alt?(alt_sub_sets)
      break if predicted_alt != ATN::INVALID_ALT_NUMBER
    else # In exact ambiguity mode, we never try to terminate early.
      # Just keeps scarfing until we know what the conflict is
      if PredictionMode.all_subsets_conflict?(alt_sub_sets) && PredictionMode.all_subsets_equal?(alt_sub_sets)

        found_exact_ambig = true
        predicted_alt = PredictionMode.single_viable_alt(alt_sub_sets)
        break
      end
      # else there are multiple non-conflicting subsets or
      # we're not sure what the ambiguity is yet.
      # So, keep going.
    end

    previous = reach
    if t != IntStream::EOF
      input.consume
      t = input.la(1)
    end
  end

  # If the configuration set uniquely predicts an alternative,
  # without conflict, then we know that it's a full LL decision
  # not SLL.
  if reach.unique_alt != ATN::INVALID_ALT_NUMBER
    report_context_sensitivity(dfa, predicted_alt, reach, start_index, input.index)
    return predicted_alt
  end

  report_ambiguity(dfa, d, start_index, input.index, found_exact_ambig, reach.alts, reach)

  predicted_alt
end

#existing_target_state(prev_d, t) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 200

def existing_target_state(prev_d, t)
  edges = prev_d.edges
  return nil if edges.nil? || (t + 1) < 0 || (t + 1) >= edges.length

  edges[t + 1]
end

#lookahead_name(input) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1061

def lookahead_name(input)
  token_name(input.la(1))
end

#precedence_transition(config, pt, collect_predicates, in_context, full_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 947

def precedence_transition(config, pt, collect_predicates, in_context, full_ctx)
  if @debug
    puts('PRED (collect_predicates=' << collect_predicates << ') ' << pt.precedence << '>=_p' << ', ctx dependent=true')
    unless @parser.nil?
      puts('context surrounding pred is ' << @parser.getRuleInvocationStack)
    end
  end

  c = nil
  if collect_predicates && in_context
    if full_ctx
      # In full context mode, we can evaluate predicates on-the-fly
      # during closure, which dramatically reduces the size of
      # the config sets. It also obviates the need to test predicates
      # later during conflict resolution.
      current_position = @_input.index
      @_input.seek(@_start_index)
      pred_succeeds = eval_semantic_context(pt.predicate, @_outer_context, config.alt, full_ctx)
      @_input.seek(current_position)
      if pred_succeeds
        c = ATNConfig.new
        c.atn_config3(config, pt.target) # no pred context
      end
    else
      new_sem_ctx = SemanticContext.and(config.semantic_context, pt.predicate)
      c = ATNConfig.new
      c.atn_config4(config, pt.target, new_sem_ctx)
    end
  else
    c = ATNConfig.new
    c.atn_config3(config, pt.target)
  end

  puts('config from pred transition=' << c) if @debug
  c
end

#pred_transition(config, pt, collect_predicates, in_context, full_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 984

def pred_transition(config, pt, collect_predicates, in_context, full_ctx)
  if @debug
    puts('PRED (collect_predicates=' << collect_predicates << ') ' << pt.rule_index << ':' << pt.pred_index << ', ctx dependent=' << pt.is_ctx_dependent)
    unless @parser.nil?
      puts('context surrounding pred is ' << @parser.getRuleInvocationStack)
    end
  end

  c = nil
  if collect_predicates && (!pt.is_ctx_dependent || (pt.is_ctx_dependent && in_context))

    if full_ctx
      # In full context mode, we can evaluate predicates on-the-fly
      # during closure, which dramatically reduces the size of
      # the config sets. It also obviates the need to test predicates
      # later during conflict resolution.
      current_position = @_input.index
      @_input.seek(@_start_index)
      pred_succeeds = eval_semantic_context(pt.predicate, @_outer_context, config.alt, full_ctx)
      @_input.seek(current_position)
      if pred_succeeds
        c = ATNConfig.new
        c.atn_config3(config, pt.target) # no pred context
      end
    else
      new_sem_ctx = SemanticContext.and(config.semantic_context, pt.predicate)
      c = ATNConfig.new
      c.atn_config4(config, pt.target, new_sem_ctx)
    end
  else
    c = ATNConfig.new
    c.atn_config3(config, pt.target)
  end

  puts('config from pred transition=' << c) if debug
  c
end

#predicate_dfa_state(dfa_state, decision_state) ⇒ Object

We need to test all predicates, even in DFA states that



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 252

def predicate_dfa_state(dfa_state, decision_state) # We need to test all predicates, even in DFA states that
  # uniquely predict alternative.
  nalts = decision_state.number_of_transitions
  # Update DFA so reach becomes accept state with (predicate,alt)
  # pairs if preds found for conflicting alts
  alts_to_collect_preds_from = conflicting_alts_or_unique_alt(dfa_state.configs)
  alt_to_pred = preds_for_ambig_alts(alts_to_collect_preds_from, dfa_state.configs, nalts)
  if !alt_to_pred.nil?
    dfa_state.predicates = predicate_predictions(alts_to_collect_preds_from, alt_to_pred)
    dfa_state.prediction = ATN::INVALID_ALT_NUMBER # make sure we use preds
  else # There are preds in configs but they might go away
    # when OR'd together like pend? || NONE == NONE. If neither
    # alt has preds, resolve to min alt
    dfa_state.prediction = alts_to_collect_preds_from.next_set_bit(0)
  end
end

#predicate_predictions(ambig_alts, alt_to_pred) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 585

def predicate_predictions(ambig_alts, alt_to_pred)
  pairs = []
  contains_predicate = false
  i = 1
  while i < alt_to_pred.length
    pred = alt_to_pred[i]

    if !ambig_alts.nil? && ambig_alts.get(i)
      pairs.add(DFAState.PredPrediction.new(pred, i))
    end
    contains_predicate = true if pred != SemanticContext::NONE
    i += 1
  end

  return nil unless contains_predicate

  #    puts(Arrays.to_s(alt_to_pred)+"->"+pairs)
  pairs.to_a
end

#preds_for_ambig_alts(ambig_alts, configs, n_alts) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 557

def preds_for_ambig_alts(ambig_alts, configs, n_alts)
  alt_to_pred = []
  i = 0
  while i < configs.length
    c = configs[i]
    if ambig_alts.get(c.alt)
      alt_to_pred[c.alt] = SemanticContext.or(alt_to_pred[c.alt], c.semantic_context)
    end
    i += 1
  end

  n_pred_alts = 0
  i = 1
  while i <= n_alts
    if alt_to_pred[i].nil?
      alt_to_pred[i] = SemanticContext::NONE
    elsif alt_to_pred[i] != SemanticContext::NONE
      n_pred_alts += 1
    end
    i += 1
  end

  # nonambig alts are nil in alt_to_pred
  alt_to_pred = nil if n_pred_alts == 0
  puts('getPredsForAmbigAlts result ' << alt_to_pred.to_s) if @debug
  alt_to_pred
end

#reachable_target(trans, ttype) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 551

def reachable_target(trans, ttype)
  return trans.target if trans.matches(ttype, 0, atn.max_token_type)

  nil
end

#remove_all_configs_not_in_rule_stop_state(configs, look_to_end_of_rule) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 449

def remove_all_configs_not_in_rule_stop_state(configs, look_to_end_of_rule)
  return configs if PredictionMode.all_configs_in_rule_stop_states?(configs)

  result = ATNConfigSet.new(configs.full_ctx)
  i = 0
  while i < configs.length
    config = configs[i]
    if config.state.is_a? RuleStopState
      result.add(config, @merge_cache)
      i += 1
      next
    end

    if look_to_end_of_rule && config.state.only_has_epsilon_transitions
      next_tokens = atn.next_tokens(config.state)
      if next_tokens.include?(Token::EPSILON)
        end_of_rule_state = atn.rule_to_stop_state[config.state.rule_index]
        atncfg = ATNConfig.new
        atncfg.atn_config3(config, end_of_rule_state)
        result.add(atncfg, @merge_cache)
      end
    end

    i += 1
  end

  result
end

#report_ambiguity(dfa, _d, start_index, stop_index, exact, ambig_alts, configs) ⇒ Object

configs that LL not SLL considered conflicting



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1156

def report_ambiguity(dfa, _d, start_index, stop_index, exact, ambig_alts, configs) # configs that LL not SLL considered conflicting
  if @debug || @retry_debug
    interval = Interval.of(start_index, stop_index)
    puts('reportAmbiguity ' << ambig_alts.to_s << ':' << configs.to_s << ', input=' << @parser._input.text2(interval).to_s)
  end
  unless @parser.nil?
    @parser.error_listener_dispatch.report_ambiguity(@parser, dfa, start_index, stop_index, exact, ambig_alts, configs)
  end
end

#report_attempting_full_context(dfa, conflict_alts, configs, start_index, stop_index) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1136

def report_attempting_full_context(dfa, conflict_alts, configs, start_index, stop_index)
  if @debug || @retry_debug
    interval = Interval.of(start_index, stop_index)
    puts('reportAttemptingFullContext decision=' << dfa.decision.to_s << ':' << configs.to_s << ', input=' << @parser._input.text2(interval).to_s)
  end
  unless @parser.nil?
    @parser.error_listener_dispatch.report_attempting_full_context(@parser, dfa, start_index, stop_index, conflict_alts, configs)
  end
end

#report_context_sensitivity(dfa, prediction, configs, start_index, stop_index) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1146

def report_context_sensitivity(dfa, prediction, configs, start_index, stop_index)
  if @debug || @retry_debug
    interval = Interval.of(start_index, stop_index)
    puts('reportContextSensitivity decision=' << dfa.decision.to_s << ':' << configs.to_s << ', input=' << @parser._input.text2(interval).to_s)
  end
  unless @parser.nil?
    @parser.error_listener_dispatch.report_context_sensitivity(@parser, dfa, start_index, stop_index, prediction, configs)
  end
end

#rule_name(index) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 899

def rule_name(index)
  return @parser.rule_names[index] if !@parser.nil? && index >= 0

  '<rule ' << index << '>'
end

#rule_transition(config, t) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1022

def rule_transition(config, t)
  if @debug
    puts('CALL rule ' << rule_name(t.target.rule_index) << ', ctx=' << config.context.to_s)
  end

  return_state = t.follow_state
  new_context = SingletonPredictionContext.new(config.context, return_state.state_number)
  c = ATNConfig.new
  c.atn_config6(config, t.target, new_context)
  c
end

#split_according_to_semantic_validity(configs, outer_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 636

def split_according_to_semantic_validity(configs, outer_ctx)
  succeeded = ATNConfigSet.new(configs.full_ctx)
  failed = ATNConfigSet.new(configs.full_ctx)
  i = 0
  while i < configs.configs.length
    c = configs.configs[i]
    if c.semantic_context != SemanticContext::NONE
      predicate_evaluation_result = eval_semantic_context(c.semantic_context, outer_ctx, c.alt, configs.full_ctx)
      if predicate_evaluation_result
        succeeded.add(c)
      else
        failed.add(c)
      end
    else
      succeeded.add(c)
    end
    i += 1
  end

  pair = OpenStruct.new
  pair.a = succeeded
  pair.b = failed
  pair
end

#syn_valid_or_sem_invalid_alt_that_finished_decision_entry_rule(configs, outer_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 605

def syn_valid_or_sem_invalid_alt_that_finished_decision_entry_rule(configs, outer_ctx)
  sets = split_according_to_semantic_validity(configs, outer_ctx)
  sem_valid_configs = sets.a
  sem_invalid_configs = sets.b
  alt = alt_that_finished_decision_entry_rule(sem_valid_configs)
  return alt if alt != ATN::INVALID_ALT_NUMBER # semantically/syntactically viable path exists

  # Is there a syntactically valid path with a failed pred?
  unless sem_invalid_configs.empty?
    alt = alt_that_finished_decision_entry_rule(sem_invalid_configs)
    return alt if alt != ATN::INVALID_ALT_NUMBER # syntactically viable path exists
  end
  ATN::INVALID_ALT_NUMBER
end

#token_name(t) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1049

def token_name(t)
  return 'EOF' if t == Token::EOF

  vocabulary = !@parser.nil? ? @parser.get_vocabulary : VocabularyImpl.EMPTY_VOCABULARY
  display_name = vocabulary.display_name(t)
  return display_name if display_name == t.to_s

  result = ''
  result << display_name
  result << '<' << t.to_s << '>'
end

#unique_alt(configs) ⇒ Object 



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# File 'lib/antlr4/runtime/parser_atn_simulator.rb', line 1084

def unique_alt(configs)
  alt = ATN::INVALID_ALT_NUMBER
  i = 0
  while i < configs.configs.length
    c = configs.configs[i]
    if alt == ATN::INVALID_ALT_NUMBER
      alt = c.alt # found first alt
    elsif c.alt != alt
      return ATN::INVALID_ALT_NUMBER
    end
    i += 1
  end
  alt
end