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Edit File : state.rb \| Size : 19.81 KB
#-- # # # # Copyright (c) 1999-2006 Minero Aoki # # This program is free software. # You can distribute/modify this program under the same terms of ruby. # see the file "COPYING". # #++ require 'racc/iset' require 'racc/statetransitiontable' require 'racc/exception' require 'forwardable' module Racc # A table of LALR states. class States include Enumerable def initialize(grammar, debug_flags = DebugFlags.new) @grammar = grammar @symboltable = grammar.symboltable @d_state = debug_flags.state @d_la = debug_flags.la @d_prec = debug_flags.prec @states = [] @statecache = {} @actions = ActionTable.new(@grammar, self) @nfa_computed = false @dfa_computed = false end attr_reader :grammar attr_reader :actions def size @states.size end def inspect '#<state table>' end alias to_s inspect def [](i) @states[i] end def each_state(&block) @states.each(&block) end alias each each_state def each_index(&block) @states.each_index(&block) end extend Forwardable def_delegator "@actions", :shift_n def_delegator "@actions", :reduce_n def_delegator "@actions", :nt_base def should_report_srconflict? srconflict_exist? and (n_srconflicts() != @grammar.n_expected_srconflicts) end def srconflict_exist? n_srconflicts() != 0 end def n_srconflicts @n_srconflicts \|\|= inject(0) {\|sum, st\| sum + st.n_srconflicts } end def rrconflict_exist? n_rrconflicts() != 0 end def n_rrconflicts @n_rrconflicts \|\|= inject(0) {\|sum, st\| sum + st.n_rrconflicts } end def state_transition_table @state_transition_table \|\|= StateTransitionTable.generate(self.dfa) end # # NFA (Non-deterministic Finite Automaton) Computation # public def nfa return self if @nfa_computed compute_nfa @nfa_computed = true self end private def compute_nfa @grammar.init # add state 0 core_to_state [ @grammar[0].ptrs[0] ] # generate LALR states cur = 0 @gotos = [] while cur < @states.size generate_states @states[cur] # state is added here cur += 1 end @actions.init end def generate_states(state) puts "dstate: #{state}" if @d_state table = {} state.closure.each do \|ptr\| if sym = ptr.dereference addsym table, sym, ptr.next end end table.each do \|sym, core\| puts "dstate: sym=#{sym} ncore=#{core}" if @d_state dest = core_to_state(core.to_a) state.goto_table[sym] = dest id = sym.nonterminal?() ? @gotos.size : nil g = Goto.new(id, sym, state, dest) @gotos.push g if sym.nonterminal? state.gotos[sym] = g puts "dstate: #{state.ident} --#{sym}--> #{dest.ident}" if @d_state # check infinite recursion if state.ident == dest.ident and state.closure.size == 1 raise CompileError, sprintf("Infinite recursion: state %d, with rule %d", state.ident, state.ptrs[0].rule.ident) end end end def addsym(table, sym, ptr) unless s = table[sym] table[sym] = s = ISet.new end s.add ptr end def core_to_state(core) # # convert CORE to a State object. # If matching state does not exist, create it and add to the table. # k = fingerprint(core) unless dest = @statecache[k] # not registered yet dest = State.new(@states.size, core) @states.push dest @statecache[k] = dest puts "core_to_state: create state ID #{dest.ident}" if @d_state else if @d_state puts "core_to_state: dest is cached ID #{dest.ident}" puts "core_to_state: dest core #{dest.core.join(' ')}" end end dest end def fingerprint(arr) arr.map {\|i\| i.ident }.pack('L') end # # DFA (Deterministic Finite Automaton) Generation # public def dfa return self if @dfa_computed nfa compute_dfa @dfa_computed = true self end private def compute_dfa la = lookahead() @states.each do \|state\| state.la = la resolve state end set_accept @states.each do \|state\| pack state end check_useless end def lookahead # # lookahead algorithm ver.3 -- from bison 1.26 # gotos = @gotos if @d_la puts "\n--- goto ---" gotos.each_with_index {\|g, i\| print i, ' '; p g } end ### initialize_LA() ### set_goto_map() la_rules = [] @states.each do \|state\| state.check_la la_rules end ### initialize_F() f = create_tmap(gotos.size) reads = [] edge = [] gotos.each do \|goto\| goto.to_state.goto_table.each do \|t, st\| if t.terminal? f[goto.ident] \|= (1 << t.ident) elsif t.nullable? edge.push goto.to_state.gotos[t].ident end end if edge.empty? reads.push nil else reads.push edge edge = [] end end digraph f, reads if @d_la puts "\n--- F1 (reads) ---" print_tab gotos, reads, f end ### build_relations() ### compute_FOLLOWS path = nil edge = [] lookback = Array.new(la_rules.size, nil) includes = [] gotos.each do \|goto\| goto.symbol.heads.each do \|ptr\| path = record_path(goto.from_state, ptr.rule) lastgoto = path.last st = lastgoto ? lastgoto.to_state : goto.from_state if st.conflict? addrel lookback, st.rruleid(ptr.rule), goto end path.reverse_each do \|g\| break if g.symbol.terminal? edge.push g.ident break unless g.symbol.nullable? end end if edge.empty? includes.push nil else includes.push edge edge = [] end end includes = transpose(includes) digraph f, includes if @d_la puts "\n--- F2 (includes) ---" print_tab gotos, includes, f end ### compute_lookaheads la = create_tmap(la_rules.size) lookback.each_with_index do \|arr, i\| if arr arr.each do \|g\| la[i] \|= f[g.ident] end end end if @d_la puts "\n--- LA (lookback) ---" print_tab la_rules, lookback, la end la end def create_tmap(size) Array.new(size, 0) # use Integer as bitmap end def addrel(tbl, i, item) if a = tbl[i] a.push item else tbl[i] = [item] end end def record_path(begst, rule) st = begst path = [] rule.symbols.each do \|t\| goto = st.gotos[t] path.push goto st = goto.to_state end path end def transpose(rel) new = Array.new(rel.size, nil) rel.each_with_index do \|arr, idx\| if arr arr.each do \|i\| addrel new, i, idx end end end new end def digraph(map, relation) n = relation.size index = Array.new(n, nil) vertices = [] @infinity = n + 2 index.each_index do \|i\| if not index[i] and relation[i] traverse i, index, vertices, map, relation end end end def traverse(i, index, vertices, map, relation) vertices.push i index[i] = height = vertices.size if rp = relation[i] rp.each do \|proci\| unless index[proci] traverse proci, index, vertices, map, relation end if index[i] > index[proci] # circulative recursion !!! index[i] = index[proci] end map[i] \|= map[proci] end end if index[i] == height while true proci = vertices.pop index[proci] = @infinity break if i == proci map[proci] \|= map[i] end end end # for debug def print_atab(idx, tab) tab.each_with_index do \|i,ii\| printf '%-20s', idx[ii].inspect p i end end def print_tab(idx, rel, tab) tab.each_with_index do \|bin,i\| print i, ' ', idx[i].inspect, ' << '; p rel[i] print ' ' each_t(@symboltable, bin) {\|t\| print ' ', t } puts end end # for debug def print_tab_i(idx, rel, tab, i) bin = tab[i] print i, ' ', idx[i].inspect, ' << '; p rel[i] print ' ' each_t(@symboltable, bin) {\|t\| print ' ', t } end # for debug def printb(i) each_t(@symboltable, i) do \|t\| print t, ' ' end puts end def each_t(tbl, set) 0.upto( set.size ) do \|i\| (0..7).each do \|ii\| if set[idx = i 8 + ii] == 1 yield tbl[idx] end end end end # # resolve # def resolve(state) if state.conflict? resolve_rr state, state.ritems resolve_sr state, state.stokens else if state.rrules.empty? # shift state.stokens.each do \|t\| state.action[t] = @actions.shift(state.goto_table[t]) end else # reduce state.defact = @actions.reduce(state.rrules[0]) end end end def resolve_rr(state, r) r.each do \|item\| item.each_la(@symboltable) do \|t\| act = state.action[t] if act unless act.kind_of?(Reduce) raise "racc: fatal: #{act.class} in action table" end # Cannot resolve R/R conflict (on t). # Reduce with upper rule as default. state.rr_conflict act.rule, item.rule, t else # No conflict. state.action[t] = @actions.reduce(item.rule) end end end end def resolve_sr(state, s) s.each do \|stok\| goto = state.goto_table[stok] act = state.action[stok] unless act # no conflict state.action[stok] = @actions.shift(goto) else unless act.kind_of?(Reduce) puts 'DEBUG -------------------------------' p stok p act state.action.each do \|k,v\| print k.inspect, ' ', v.inspect, "\n" end raise "racc: fatal: #{act.class} in action table" end # conflict on stok rtok = act.rule.precedence case do_resolve_sr(stok, rtok) when :Reduce # action is already set when :Shift # overwrite act.decref state.action[stok] = @actions.shift(goto) when :Error act.decref state.action[stok] = @actions.error when :CantResolve # shift as default act.decref state.action[stok] = @actions.shift(goto) state.sr_conflict stok, act.rule end end end end ASSOC = { :Left => :Reduce, :Right => :Shift, :Nonassoc => :Error } def do_resolve_sr(stok, rtok) puts "resolve_sr: s/r conflict: rtok=#{rtok}, stok=#{stok}" if @d_prec unless rtok and rtok.precedence puts "resolve_sr: no prec for #{rtok}(R)" if @d_prec return :CantResolve end rprec = rtok.precedence unless stok and stok.precedence puts "resolve_sr: no prec for #{stok}(S)" if @d_prec return :CantResolve end sprec = stok.precedence ret = if rprec == sprec ASSOC[rtok.assoc] or raise "racc: fatal: #{rtok}.assoc is not Left/Right/Nonassoc" else (rprec > sprec) ? (:Reduce) : (:Shift) end puts "resolve_sr: resolved as #{ret.id2name}" if @d_prec ret end # # complete # def set_accept anch = @symboltable.anchor init_state = @states[0].goto_table[@grammar.start] targ_state = init_state.action[anch].goto_state acc_state = targ_state.action[anch].goto_state acc_state.action.clear acc_state.goto_table.clear acc_state.defact = @actions.accept end def pack(state) ### find most frequently used reduce rule act = state.action arr = Array.new(@grammar.size, 0) act.each do \|t, a\| arr[a.ruleid] += 1 if a.kind_of?(Reduce) end i = arr.max s = (i > 0) ? arr.index(i) : nil ### set & delete default action if s r = @actions.reduce(s) if not state.defact or state.defact == r act.delete_if {\|t, a\| a == r } state.defact = r end else state.defact \|\|= @actions.error end end def check_useless used = [] @actions.each_reduce do \|act\| if not act or act.refn == 0 act.rule.useless = true else t = act.rule.target used[t.ident] = t end end @symboltable.nt_base.upto(@symboltable.nt_max - 1) do \|n\| unless used[n] @symboltable[n].useless = true end end end end # class StateTable # A LALR state. class State def initialize(ident, core) @ident = ident @core = core @goto_table = {} @gotos = {} @stokens = nil @ritems = nil @action = {} @defact = nil @rrconf = nil @srconf = nil @closure = make_closure(@core) end attr_reader :ident alias stateid ident alias hash ident attr_reader :core attr_reader :closure attr_reader :goto_table attr_reader :gotos attr_reader :stokens attr_reader :ritems attr_reader :rrules attr_reader :action attr_accessor :defact # default action attr_reader :rrconf attr_reader :srconf def inspect "<state #{@ident}>" end alias to_s inspect def ==(oth) @ident == oth.ident end alias eql? == def make_closure(core) set = ISet.new core.each do \|ptr\| set.add ptr if t = ptr.dereference and t.nonterminal? set.update_a t.expand end end set.to_a end def check_la(la_rules) @conflict = false s = [] r = [] @closure.each do \|ptr\| if t = ptr.dereference if t.terminal? s[t.ident] = t if t.ident == 1 # $error @conflict = true end end else r.push ptr.rule end end unless r.empty? if not s.empty? or r.size > 1 @conflict = true end end s.compact! @stokens = s @rrules = r if @conflict @la_rules_i = la_rules.size @la_rules = r.map {\|i\| i.ident } la_rules.concat r else @la_rules_i = @la_rules = nil end end def conflict? @conflict end def rruleid(rule) if i = @la_rules.index(rule.ident) @la_rules_i + i else puts '/// rruleid' p self p rule p @rrules p @la_rules_i raise 'racc: fatal: cannot get reduce rule id' end end def la=(la) return unless @conflict i = @la_rules_i @ritems = r = [] @rrules.each do \|rule\| r.push Item.new(rule, la[i]) i += 1 end end def rr_conflict(high, low, ctok) c = RRconflict.new(@ident, high, low, ctok) @rrconf \|\|= {} if a = @rrconf[ctok] a.push c else @rrconf[ctok] = [c] end end def sr_conflict(shift, reduce) c = SRconflict.new(@ident, shift, reduce) @srconf \|\|= {} if a = @srconf[shift] a.push c else @srconf[shift] = [c] end end def n_srconflicts @srconf ? @srconf.size : 0 end def n_rrconflicts @rrconf ? @rrconf.size : 0 end end # class State # # Represents a transition on the grammar. # "Real goto" means a transition by nonterminal, # but this class treats also terminal's. # If one is a terminal transition, .ident returns nil. # class Goto def initialize(ident, sym, from, to) @ident = ident @symbol = sym @from_state = from @to_state = to end attr_reader :ident attr_reader :symbol attr_reader :from_state attr_reader :to_state def inspect "(#{@from_state.ident}-#{@symbol}->#{@to_state.ident})" end end # LALR item. A set of rule and its lookahead tokens. class Item def initialize(rule, la) @rule = rule @la = la end attr_reader :rule attr_reader :la def each_la(tbl) la = @la 0.upto(la.size - 1) do \|i\| (0..7).each do \|ii\| if la[idx = i * 8 + ii] == 1 yield tbl[idx] end end end end end # The table of LALR actions. Actions are either of # Shift, Reduce, Accept and Error. class ActionTable def initialize(rt, st) @grammar = rt @statetable = st @reduce = [] @shift = [] @accept = nil @error = nil end def init @grammar.each do \|rule\| @reduce.push Reduce.new(rule) end @statetable.each do \|state\| @shift.push Shift.new(state) end @accept = Accept.new @error = Error.new end def reduce_n @reduce.size end def reduce(i) case i when Rule then i = i.ident when Integer then ; else raise "racc: fatal: wrong class #{i.class} for reduce" end r = @reduce[i] or raise "racc: fatal: reduce action #{i.inspect} not exist" r.incref r end def each_reduce(&block) @reduce.each(&block) end def shift_n @shift.size end def shift(i) case i when State then i = i.ident when Integer then ; else raise "racc: fatal: wrong class #{i.class} for shift" end @shift[i] or raise "racc: fatal: shift action #{i} does not exist" end def each_shift(&block) @shift.each(&block) end attr_reader :accept attr_reader :error end class Shift def initialize(goto) @goto_state = goto end attr_reader :goto_state def goto_id @goto_state.ident end def inspect "<shift #{@goto_state.ident}>" end end class Reduce def initialize(rule) @rule = rule @refn = 0 end attr_reader :rule attr_reader :refn def ruleid @rule.ident end def inspect "<reduce #{@rule.ident}>" end def incref @refn += 1 end def decref @refn -= 1 raise 'racc: fatal: act.refn < 0' if @refn < 0 end end class Accept def inspect "<accept>" end end class Error def inspect "<error>" end end class SRconflict def initialize(sid, shift, reduce) @stateid = sid @shift = shift @reduce = reduce end attr_reader :stateid attr_reader :shift attr_reader :reduce def to_s sprintf('state %d: S/R conflict rule %d reduce and shift %s', @stateid, @reduce.ruleid, @shift.to_s) end end class RRconflict def initialize(sid, high, low, tok) @stateid = sid @high_prec = high @low_prec = low @token = tok end attr_reader :stateid attr_reader :high_prec attr_reader :low_prec attr_reader :token def to_s sprintf('state %d: R/R conflict with rule %d and %d on %s', @stateid, @high_prec.ident, @low_prec.ident, @token.to_s) end end end Back

Edit File : state.rb | Size : 19.81 KB

#--
#
#
#
# Copyright (c) 1999-2006 Minero Aoki
#
# This program is free software.
# You can distribute/modify this program under the same terms of ruby.
# see the file "COPYING".
#
#++

require 'racc/iset'
require 'racc/statetransitiontable'
require 'racc/exception'
require 'forwardable'

module Racc

# A table of LALR states.
  class States

include Enumerable

def initialize(grammar, debug_flags = DebugFlags.new)
      @grammar = grammar
      @symboltable = grammar.symboltable
      @d_state = debug_flags.state
      @d_la    = debug_flags.la
      @d_prec  = debug_flags.prec
      @states = []
      @statecache = {}
      @actions = ActionTable.new(@grammar, self)
      @nfa_computed = false
      @dfa_computed = false
    end

attr_reader :grammar
    attr_reader :actions

def size
      @states.size
    end

def inspect
      '#<state table>'
    end

alias to_s inspect

def [](i)
      @states[i]
    end

def each_state(&block)
      @states.each(&block)
    end

alias each each_state

def each_index(&block)
      @states.each_index(&block)
    end

extend Forwardable

def_delegator "@actions", :shift_n
    def_delegator "@actions", :reduce_n
    def_delegator "@actions", :nt_base

def should_report_srconflict?
      srconflict_exist? and
          (n_srconflicts() != @grammar.n_expected_srconflicts)
    end

def srconflict_exist?
      n_srconflicts() != 0
    end

def n_srconflicts
      @n_srconflicts ||= inject(0) {|sum, st| sum + st.n_srconflicts }
    end

def rrconflict_exist?
      n_rrconflicts() != 0
    end

def n_rrconflicts
      @n_rrconflicts ||= inject(0) {|sum, st| sum + st.n_rrconflicts }
    end

def state_transition_table
      @state_transition_table ||= StateTransitionTable.generate(self.dfa)
    end

#
    # NFA (Non-deterministic Finite Automaton) Computation
    #

public

def nfa
      return self if @nfa_computed
      compute_nfa
      @nfa_computed = true
      self
    end

private

def compute_nfa
      @grammar.init
      # add state 0
      core_to_state  [ @grammar[0].ptrs[0] ]
      # generate LALR states
      cur = 0
      @gotos = []
      while cur < @states.size
        generate_states @states[cur]   # state is added here
        cur += 1
      end
      @actions.init
    end

def generate_states(state)
      puts "dstate: #{state}" if @d_state

table = {}
      state.closure.each do |ptr|
        if sym = ptr.dereference
          addsym table, sym, ptr.next
        end
      end
      table.each do |sym, core|
        puts "dstate: sym=#{sym} ncore=#{core}" if @d_state

dest = core_to_state(core.to_a)
        state.goto_table[sym] = dest
        id = sym.nonterminal?() ? @gotos.size : nil
        g = Goto.new(id, sym, state, dest)
        @gotos.push g if sym.nonterminal?
        state.gotos[sym] = g
        puts "dstate: #{state.ident} --#{sym}--> #{dest.ident}" if @d_state

# check infinite recursion
        if state.ident == dest.ident and state.closure.size == 1
          raise CompileError,
              sprintf("Infinite recursion: state %d, with rule %d",
                      state.ident, state.ptrs[0].rule.ident)
        end
      end
    end

def addsym(table, sym, ptr)
      unless s = table[sym]
        table[sym] = s = ISet.new
      end
      s.add ptr
    end

def core_to_state(core)
      #
      # convert CORE to a State object.
      # If matching state does not exist, create it and add to the table.
      #

k = fingerprint(core)
      unless dest = @statecache[k]
        # not registered yet
        dest = State.new(@states.size, core)
        @states.push dest

@statecache[k] = dest

puts "core_to_state: create state   ID #{dest.ident}" if @d_state
      else
        if @d_state
          puts "core_to_state: dest is cached ID #{dest.ident}"
          puts "core_to_state: dest core #{dest.core.join(' ')}"
        end
      end

dest
    end

def fingerprint(arr)
      arr.map {|i| i.ident }.pack('L*')
    end

#
    # DFA (Deterministic Finite Automaton) Generation
    #

public

def dfa
      return self if @dfa_computed
      nfa
      compute_dfa
      @dfa_computed = true
      self
    end

private

def compute_dfa
      la = lookahead()
      @states.each do |state|
        state.la = la
        resolve state
      end
      set_accept
      @states.each do |state|
        pack state
      end
      check_useless
    end

def lookahead
      #
      # lookahead algorithm ver.3 -- from bison 1.26
      #

gotos = @gotos
      if @d_la
        puts "\n--- goto ---"
        gotos.each_with_index {|g, i| print i, ' '; p g }
      end

### initialize_LA()
      ### set_goto_map()
      la_rules = []
      @states.each do |state|
        state.check_la la_rules
      end

### initialize_F()
      f     = create_tmap(gotos.size)
      reads = []
      edge  = []
      gotos.each do |goto|
        goto.to_state.goto_table.each do |t, st|
          if t.terminal?
            f[goto.ident] |= (1 << t.ident)
          elsif t.nullable?
            edge.push goto.to_state.gotos[t].ident
          end
        end
        if edge.empty?
          reads.push nil
        else
          reads.push edge
          edge = []
        end
      end
      digraph f, reads
      if @d_la
        puts "\n--- F1 (reads) ---"
        print_tab gotos, reads, f
      end

### build_relations()
      ### compute_FOLLOWS
      path = nil
      edge = []
      lookback = Array.new(la_rules.size, nil)
      includes = []
      gotos.each do |goto|
        goto.symbol.heads.each do |ptr|
          path = record_path(goto.from_state, ptr.rule)
          lastgoto = path.last
          st = lastgoto ? lastgoto.to_state : goto.from_state
          if st.conflict?
            addrel lookback, st.rruleid(ptr.rule), goto
          end
          path.reverse_each do |g|
            break if     g.symbol.terminal?
            edge.push    g.ident
            break unless g.symbol.nullable?
          end
        end
        if edge.empty?
          includes.push nil
        else
          includes.push edge
          edge = []
        end
      end
      includes = transpose(includes)
      digraph f, includes
      if @d_la
        puts "\n--- F2 (includes) ---"
        print_tab gotos, includes, f
      end

### compute_lookaheads
      la = create_tmap(la_rules.size)
      lookback.each_with_index do |arr, i|
        if arr
          arr.each do |g|
            la[i] |= f[g.ident]
          end
        end
      end
      if @d_la
        puts "\n--- LA (lookback) ---"
        print_tab la_rules, lookback, la
      end

la
    end

def create_tmap(size)
      Array.new(size, 0)   # use Integer as bitmap
    end

def addrel(tbl, i, item)
      if a = tbl[i]
        a.push item
      else
        tbl[i] = [item]
      end
    end

def record_path(begst, rule)
      st = begst
      path = []
      rule.symbols.each do |t|
        goto = st.gotos[t]
        path.push goto
        st = goto.to_state
      end
      path
    end

def transpose(rel)
      new = Array.new(rel.size, nil)
      rel.each_with_index do |arr, idx|
        if arr
          arr.each do |i|
            addrel new, i, idx
          end
        end
      end
      new
    end

def digraph(map, relation)
      n = relation.size
      index    = Array.new(n, nil)
      vertices = []
      @infinity = n + 2

index.each_index do |i|
        if not index[i] and relation[i]
          traverse i, index, vertices, map, relation
        end
      end
    end

def traverse(i, index, vertices, map, relation)
      vertices.push i
      index[i] = height = vertices.size

if rp = relation[i]
        rp.each do |proci|
          unless index[proci]
            traverse proci, index, vertices, map, relation
          end
          if index[i] > index[proci]
            # circulative recursion !!!
            index[i] = index[proci]
          end
          map[i] |= map[proci]
        end
      end

if index[i] == height
        while true
          proci = vertices.pop
          index[proci] = @infinity
          break if i == proci

map[proci] |= map[i]
        end
      end
    end

# for debug
    def print_atab(idx, tab)
      tab.each_with_index do |i,ii|
        printf '%-20s', idx[ii].inspect
        p i
      end
    end

def print_tab(idx, rel, tab)
      tab.each_with_index do |bin,i|
        print i, ' ', idx[i].inspect, ' << '; p rel[i]
        print '  '
        each_t(@symboltable, bin) {|t| print ' ', t }
        puts
      end
    end

# for debug
    def print_tab_i(idx, rel, tab, i)
      bin = tab[i]
      print i, ' ', idx[i].inspect, ' << '; p rel[i]
      print '  '
      each_t(@symboltable, bin) {|t| print ' ', t }
    end

# for debug
    def printb(i)
      each_t(@symboltable, i) do |t|
        print t, ' '
      end
      puts
    end

def each_t(tbl, set)
      0.upto( set.size ) do |i|
        (0..7).each do |ii|
          if set[idx = i * 8 + ii] == 1
            yield tbl[idx]
          end
        end
      end
    end

#
    # resolve
    #

def resolve(state)
      if state.conflict?
        resolve_rr state, state.ritems
        resolve_sr state, state.stokens
      else
        if state.rrules.empty?
          # shift
          state.stokens.each do |t|
            state.action[t] = @actions.shift(state.goto_table[t])
          end
        else
          # reduce
          state.defact = @actions.reduce(state.rrules[0])
        end
      end
    end

def resolve_rr(state, r)
      r.each do |item|
        item.each_la(@symboltable) do |t|
          act = state.action[t]
          if act
            unless act.kind_of?(Reduce)
              raise "racc: fatal: #{act.class} in action table"
            end
            # Cannot resolve R/R conflict (on t).
            # Reduce with upper rule as default.
            state.rr_conflict act.rule, item.rule, t
          else
            # No conflict.
            state.action[t] = @actions.reduce(item.rule)
          end
        end
      end
    end

def resolve_sr(state, s)
      s.each do |stok|
        goto = state.goto_table[stok]
        act = state.action[stok]

unless act
          # no conflict
          state.action[stok] = @actions.shift(goto)
        else
          unless act.kind_of?(Reduce)
            puts 'DEBUG -------------------------------'
            p stok
            p act
            state.action.each do |k,v|
              print k.inspect, ' ', v.inspect, "\n"
            end
            raise "racc: fatal: #{act.class} in action table"
          end

# conflict on stok

rtok = act.rule.precedence
          case do_resolve_sr(stok, rtok)
          when :Reduce
            # action is already set

when :Shift
            # overwrite
            act.decref
            state.action[stok] = @actions.shift(goto)

when :Error
            act.decref
            state.action[stok] = @actions.error

when :CantResolve
            # shift as default
            act.decref
            state.action[stok] = @actions.shift(goto)
            state.sr_conflict stok, act.rule
          end
        end
      end
    end

ASSOC = {
      :Left     => :Reduce,
      :Right    => :Shift,
      :Nonassoc => :Error
    }

def do_resolve_sr(stok, rtok)
      puts "resolve_sr: s/r conflict: rtok=#{rtok}, stok=#{stok}" if @d_prec

unless rtok and rtok.precedence
        puts "resolve_sr: no prec for #{rtok}(R)" if @d_prec
        return :CantResolve
      end
      rprec = rtok.precedence

unless stok and stok.precedence
        puts "resolve_sr: no prec for #{stok}(S)" if @d_prec
        return :CantResolve
      end
      sprec = stok.precedence

ret = if rprec == sprec
              ASSOC[rtok.assoc] or
                  raise "racc: fatal: #{rtok}.assoc is not Left/Right/Nonassoc"
            else
              (rprec > sprec) ? (:Reduce) : (:Shift)
            end

puts "resolve_sr: resolved as #{ret.id2name}" if @d_prec
      ret
    end

#
    # complete
    #

def set_accept
      anch = @symboltable.anchor
      init_state = @states[0].goto_table[@grammar.start]
      targ_state = init_state.action[anch].goto_state
      acc_state  = targ_state.action[anch].goto_state

acc_state.action.clear
      acc_state.goto_table.clear
      acc_state.defact = @actions.accept
    end

def pack(state)
      ### find most frequently used reduce rule
      act = state.action
      arr = Array.new(@grammar.size, 0)
      act.each do |t, a|
        arr[a.ruleid] += 1  if a.kind_of?(Reduce)
      end
      i = arr.max
      s = (i > 0) ? arr.index(i) : nil

### set & delete default action
      if s
        r = @actions.reduce(s)
        if not state.defact or state.defact == r
          act.delete_if {|t, a| a == r }
          state.defact = r
        end
      else
        state.defact ||= @actions.error
      end
    end

def check_useless
      used = []
      @actions.each_reduce do |act|
        if not act or act.refn == 0
          act.rule.useless = true
        else
          t = act.rule.target
          used[t.ident] = t
        end
      end
      @symboltable.nt_base.upto(@symboltable.nt_max - 1) do |n|
        unless used[n]
          @symboltable[n].useless = true
        end
      end
    end

end   # class StateTable

# A LALR state.
  class State

def initialize(ident, core)
      @ident = ident
      @core = core
      @goto_table = {}
      @gotos = {}
      @stokens = nil
      @ritems = nil
      @action = {}
      @defact = nil
      @rrconf = nil
      @srconf = nil

@closure = make_closure(@core)
    end

attr_reader :ident
    alias stateid ident
    alias hash ident

attr_reader :core
    attr_reader :closure

attr_reader :goto_table
    attr_reader :gotos

attr_reader :stokens
    attr_reader :ritems
    attr_reader :rrules

attr_reader :action
    attr_accessor :defact   # default action

attr_reader :rrconf
    attr_reader :srconf

def inspect
      "<state #{@ident}>"
    end

alias to_s inspect

def ==(oth)
      @ident == oth.ident
    end

alias eql? ==

def make_closure(core)
      set = ISet.new
      core.each do |ptr|
        set.add ptr
        if t = ptr.dereference and t.nonterminal?
          set.update_a t.expand
        end
      end
      set.to_a
    end

def check_la(la_rules)
      @conflict = false
      s = []
      r = []
      @closure.each do |ptr|
        if t = ptr.dereference
          if t.terminal?
            s[t.ident] = t
            if t.ident == 1    # $error
              @conflict = true
            end
          end
        else
          r.push ptr.rule
        end
      end
      unless r.empty?
        if not s.empty? or r.size > 1
          @conflict = true
        end
      end
      s.compact!
      @stokens  = s
      @rrules = r

if @conflict
        @la_rules_i = la_rules.size
        @la_rules = r.map {|i| i.ident }
        la_rules.concat r
      else
        @la_rules_i = @la_rules = nil
      end
    end

def conflict?
      @conflict
    end

def rruleid(rule)
      if i = @la_rules.index(rule.ident)
        @la_rules_i + i
      else
        puts '/// rruleid'
        p self
        p rule
        p @rrules
        p @la_rules_i
        raise 'racc: fatal: cannot get reduce rule id'
      end
    end

def la=(la)
      return unless @conflict
      i = @la_rules_i
      @ritems = r = []
      @rrules.each do |rule|
        r.push Item.new(rule, la[i])
        i += 1
      end
    end

def rr_conflict(high, low, ctok)
      c = RRconflict.new(@ident, high, low, ctok)

@rrconf ||= {}
      if a = @rrconf[ctok]
        a.push c
      else
        @rrconf[ctok] = [c]
      end
    end

def sr_conflict(shift, reduce)
      c = SRconflict.new(@ident, shift, reduce)

@srconf ||= {}
      if a = @srconf[shift]
        a.push c
      else
        @srconf[shift] = [c]
      end
    end

def n_srconflicts
      @srconf ? @srconf.size : 0
    end

def n_rrconflicts
      @rrconf ? @rrconf.size : 0
    end

end   # class State

#
  # Represents a transition on the grammar.
  # "Real goto" means a transition by nonterminal,
  # but this class treats also terminal's.
  # If one is a terminal transition, .ident returns nil.
  #
  class Goto
    def initialize(ident, sym, from, to)
      @ident      = ident
      @symbol     = sym
      @from_state = from
      @to_state   = to
    end

attr_reader :ident
    attr_reader :symbol
    attr_reader :from_state
    attr_reader :to_state

def inspect
      "(#{@from_state.ident}-#{@symbol}->#{@to_state.ident})"
    end
  end

# LALR item.  A set of rule and its lookahead tokens.
  class Item
    def initialize(rule, la)
      @rule = rule
      @la  = la
    end

attr_reader :rule
    attr_reader :la

def each_la(tbl)
      la = @la
      0.upto(la.size - 1) do |i|
        (0..7).each do |ii|
          if la[idx = i * 8 + ii] == 1
            yield tbl[idx]
          end
        end
      end
    end
  end

# The table of LALR actions. Actions are either of
  # Shift, Reduce, Accept and Error.
  class ActionTable

def initialize(rt, st)
      @grammar = rt
      @statetable = st

@reduce = []
      @shift = []
      @accept = nil
      @error = nil
    end

def init
      @grammar.each do |rule|
        @reduce.push Reduce.new(rule)
      end
      @statetable.each do |state|
        @shift.push Shift.new(state)
      end
      @accept = Accept.new
      @error = Error.new
    end

def reduce_n
      @reduce.size
    end

def reduce(i)
      case i
      when Rule    then i = i.ident
      when Integer then ;
      else
        raise "racc: fatal: wrong class #{i.class} for reduce"
      end

r = @reduce[i] or raise "racc: fatal: reduce action #{i.inspect} not exist"
      r.incref
      r
    end

def each_reduce(&block)
      @reduce.each(&block)
    end

def shift_n
      @shift.size
    end

def shift(i)
      case i
      when State   then i = i.ident
      when Integer then ;
      else
        raise "racc: fatal: wrong class #{i.class} for shift"
      end

@shift[i] or raise "racc: fatal: shift action #{i} does not exist"
    end

def each_shift(&block)
      @shift.each(&block)
    end

attr_reader :accept
    attr_reader :error

end

class Shift
    def initialize(goto)
      @goto_state = goto
    end

attr_reader :goto_state

def goto_id
      @goto_state.ident
    end

def inspect
      "<shift #{@goto_state.ident}>"
    end
  end

class Reduce
    def initialize(rule)
      @rule = rule
      @refn = 0
    end

attr_reader :rule
    attr_reader :refn

def ruleid
      @rule.ident
    end

def inspect
      "<reduce #{@rule.ident}>"
    end

def incref
      @refn += 1
    end

def decref
      @refn -= 1
      raise 'racc: fatal: act.refn < 0' if @refn < 0
    end
  end

class Accept
    def inspect
      "<accept>"
    end
  end

class Error
    def inspect
      "<error>"
    end
  end

class SRconflict
    def initialize(sid, shift, reduce)
      @stateid = sid
      @shift   = shift
      @reduce  = reduce
    end

attr_reader :stateid
    attr_reader :shift
    attr_reader :reduce

def to_s
      sprintf('state %d: S/R conflict rule %d reduce and shift %s',
              @stateid, @reduce.ruleid, @shift.to_s)
    end
  end

class RRconflict
    def initialize(sid, high, low, tok)
      @stateid   = sid
      @high_prec = high
      @low_prec  = low
      @token     = tok
    end

attr_reader :stateid
    attr_reader :high_prec
    attr_reader :low_prec
    attr_reader :token

def to_s
      sprintf('state %d: R/R conflict with rule %d and %d on %s',
              @stateid, @high_prec.ident, @low_prec.ident, @token.to_s)
    end
  end

end

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