Class: Rly::Yacc

Inherits:
Object
  • Object
show all
Defined in:
lib/rly/yacc.rb,
lib/rly/helpers.rb

Direct Known Subclasses

RuleParser

Class Attribute Summary collapse

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(lex = nil) ⇒ Yacc

Returns a new instance of Yacc

Raises:

  • (ArgumentError)

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# File 'lib/rly/yacc.rb', line 13

def initialize(lex=nil)
  raise ArgumentError.new("No lexer available") if lex == nil && self.class.lexer_class == nil
  @lex = lex || self.class.lexer_class.new

  @grammar = grammar
end

Class Attribute Details

.error_handlerObject

Returns the value of attribute error_handler


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# File 'lib/rly/yacc.rb', line 322

def error_handler
  @error_handler
end

.grammarObject

Returns the value of attribute grammar


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# File 'lib/rly/yacc.rb', line 322

def grammar
  @grammar
end

.lexer_classObject

Returns the value of attribute lexer_class


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# File 'lib/rly/yacc.rb', line 322

def lexer_class
  @lexer_class
end

.prec_rulesObject

Returns the value of attribute prec_rules


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# File 'lib/rly/yacc.rb', line 322

def prec_rules
  @prec_rules
end

.rulesObject

Returns the value of attribute rules


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# File 'lib/rly/yacc.rb', line 322

def rules
  @rules
end

.store_grammar_defObject

Returns the value of attribute store_grammar_def


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# File 'lib/rly/yacc.rb', line 322

def store_grammar_def
  @store_grammar_def
end

Instance Attribute Details

#lexObject (readonly)

Returns the value of attribute lex


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# File 'lib/rly/yacc.rb', line 11

def lex
  @lex
end

#lr_tableObject (readonly)

Returns the value of attribute lr_table


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# File 'lib/rly/yacc.rb', line 11

def lr_table
  @lr_table
end

Class Method Details

.assign_rhs(idx = 1) ⇒ Object


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# File 'lib/rly/helpers.rb', line 32

def self.assign_rhs(idx=1)
  ->(*args) {
    ret = args.shift
    idx -= 1
    ret.value = args[idx] ? args[idx].value : nil
  }
end

.collect_to_aObject


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# File 'lib/rly/helpers.rb', line 40

def self.collect_to_a
  ->(ret, val, *args) {
    ret.value = [val.value]
    vals = args[-1]
    ret.value += vals.value if vals
  }
end

.error_countObject


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# File 'lib/rly/yacc.rb', line 353

def error_count
  3
end

.lexer(&block) ⇒ Object


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# File 'lib/rly/yacc.rb', line 333

def lexer(&block)
  @lexer_class = Class.new(Lex, &block)
  nil
end

.on_error(lambda) ⇒ Object


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# File 'lib/rly/yacc.rb', line 357

def on_error(lambda)
  @error_handler = lambda
end

.parsed_rulesObject


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# File 'lib/rly/yacc.rb', line 361

def parsed_rules
  return @parsed_rules if @parsed_rules

  @parsed_rules = []
  rp = RuleParser.new
  self.rules.each do |desc, block|
    rules = rp.parse(desc)
    raise RuntimeError.new("Failed to parse rules: #{desc}") unless rules
    rules.each do |(pname, p, prec)|
      @parsed_rules << [pname, p, prec, block]
    end
  end
  @parsed_rules
end

.precedence(*prec) ⇒ Object


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# File 'lib/rly/yacc.rb', line 342

def precedence(*prec)
  assoc = prec.shift
  count = self.prec_rules.length + 1
  self.prec_rules << [assoc, prec, count]
  nil
end

.rule(desc, &block) ⇒ Object


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# File 'lib/rly/yacc.rb', line 328

def rule(desc, &block)
  self.rules << [desc, block]
  nil
end

.store_grammar(fn) ⇒ Object


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# File 'lib/rly/yacc.rb', line 324

def store_grammar(fn)
  @store_grammar_def = fn
end

.with_valuesObject

Raises:

  • (ArgumentError)

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# File 'lib/rly/helpers.rb', line 24

def self.with_values
  raise ArgumentError.new("Must pass a block") unless block_given?
  ->(*args) {
    ret = args.shift
    ret.value = yield *args.map { |a| a.value }
  }
end

Instance Method Details

#inspectObject


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# File 'lib/rly/yacc.rb', line 20

def inspect
  "#<#{self.class} ...>"
end

#parse(input = nil, trace = false) ⇒ Object


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# File 'lib/rly/yacc.rb', line 24

def parse(input=nil, trace=false)
  @trace = trace

  lookahead = nil
  lookaheadstack = []
  actions = @lr_table.lr_action
  goto = @lr_table.lr_goto
  prod = @lr_table.lr_productions
  pslice = YaccProduction.new(nil)
  errorcount = 0

  # Set up the lexer and parser objects on pslice
  pslice.lexer = @lex
  pslice.parser = self

  # If input was supplied, pass to lexer
  @lex.input(input) if input

  # Set up the state and symbol stacks
  @statestack = []
  @symstack = []

  pslice.stack = @symstack
  errtoken = nil

  # The start state is assumed to be (0,$end)
  @statestack.push(0)
  sym = YaccSymbol.new
  sym.type = :"$end"
  @symstack.push(sym)
  state = 0

  while true
    # Get the next symbol on the input.  If a lookahead symbol
    # is already set, we just use that. Otherwise, we'll pull
    # the next token off of the lookaheadstack or from the lexer

    puts "State  : #{state}" if @trace

    unless lookahead
      if lookaheadstack.empty?
        lookahead = @lex.next
      else
        lookahead = lookaheadstack.pop
      end
      unless lookahead
        lookahead = YaccSymbol.new()
        lookahead.type = :"$end"
      end
    end

    puts "Stack  : #{(@symstack[1..-1].map{|s|s.type}.join(' ') + ' ' + lookahead.inspect).lstrip}" if @trace

    # Check the action table
    ltype = lookahead.type
    t = actions[state][ltype]

    if t
      if t > 0
        # shift a symbol on the stack
        @statestack.push(t)
        state = t

        puts "Action : Shift and goto state #{t}" if @trace
        
        @symstack.push(lookahead)
        lookahead = nil

        # Decrease error count on successful shift
        errorcount -= 1 if errorcount > 0
        next
      end

      if t < 0
        # reduce a symbol on the stack, emit a production
        p = prod[-t]
        pname = p.name
        plen  = p.length

        # Get production function
        sym = YaccSymbol.new()
        sym.type = pname
        sym.value = nil

        if @trace
          if plen
            puts "Action : Reduce rule [#{p}] with [#{@symstack[[email protected]].map{|s|s.inspect}.join(', ')}] and goto state #{-t}"
          else
            puts "Action : Reduce rule [#{p}] with [] and goto state #{-t}"
          end
        end

        if plen
          targ = @symstack.pop(plen)
          targ.insert(0, sym)

          # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
          # The code enclosed in this section is duplicated
          # below as a performance optimization.  Make sure
          # changes get made in both locations.

          pslice.slice = targ
          
          begin
            # Call the grammar rule with our special slice object
            @statestack.pop(plen)
            instance_exec(*targ, &p.block)

            puts "Result : #{targ[0].inspect}" if @trace

            @symstack.push(sym)
            state = goto[@statestack[-1]][pname]
            @statestack.push(state)
          rescue YaccError
            # If an error was set. Enter error recovery state
            lookaheadstack.push(lookahead)
            @symstack.pop # FIXME: this is definitely broken
            @statestack.pop
            state = @statestack[-1]
            sym.type = :error
            lookahead = sym
            errorcount = self.class.error_count
            @errorok = false
          end
          next
          # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        else
          targ = [ sym ]

          # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
          # The code enclosed in this section is duplicated
          # below as a performance optimization.  Make sure
          # changes get made in both locations.

          pslice.slice = targ
          
          begin
            # Call the grammar rule with our special slice object
            @statestack.pop(plen)
            pslice[0] = instance_exec(*pslice, &p.block)

            puts "Result : #{targ[0].value}" if @trace

            @symstack.push(sym)
            state = goto[@statestack[-1]][pname]
            @statestack.push(state)
          rescue
            # If an error was set. Enter error recovery state
            lookaheadstack.push(lookahead)
            @symstack.pop # FIXME: this is definitely broken
            @statestack.pop
            state = @statestack[-1]
            sym.type = :error
            lookahead = sym
            errorcount = error_count
            @errorok = false
          end
          next
          # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        end
      end

      if t == 0
        n = @symstack[-1]
        result = n.value

        puts "Done   : Returning #{result}" if @trace

        return result
      end
    end

    if t == nil
      # We have some kind of parsing error here.  To handle
      # this, we are going to push the current token onto
      # the tokenstack and replace it with an 'error' token.
      # If there are any synchronization rules, they may
      # catch it.
      #
      # In addition to pushing the error token, we call call
      # the user defined p_error() function if this is the
      # first syntax error.  This function is only called if
      # errorcount == 0.
      if errorcount == 0 || @errorok == true
        errorcount = self.class.error_count
        @errorok = false
        errtoken = lookahead
        errtoken = nil if errtoken.type == :"$end"

        if self.class.error_handler
          tok = self.instance_exec(errtoken, &self.class.error_handler)

          if @errorok
            # User must have done some kind of panic
            # mode recovery on their own.  The
            # returned token is the next lookahead
            lookahead = tok
            errtoken = nil
            next
          end
        else
          if errtoken
            location_info = lookahead.location_info
            puts "Fail   : Syntax error at #{location_info}, token='#{errtoken}'" if @trace
          else
            puts "Fail   : Parse error in input. EOF" if @trace
            return nil
          end
        end
      else
        errorcount = self.class.error_count
      end

      # case 1:  the @statestack only has 1 entry on it.  If we're in this state, the
      # entire parse has been rolled back and we're completely hosed.   The token is
      # discarded and we just keep going.

      if @statestack.length <= 1 and lookahead.type != :"$end"
        lookahead = nil
        errtoken = nil
        state = 0
        # Nuke the pushback stack
        lookaheadstack = []
        next
      end

      # case 2: the @statestack has a couple of entries on it, but we're
      # at the end of the file. nuke the top entry and generate an error token

      # Start nuking entries on the stack
      if lookahead.type == :"$end"
        # Whoa. We're really hosed here. Bail out
        return nil
      end

      if lookahead.type != :error
        sym = @symstack[-1]
        if sym.type == :error
          # Hmmm. Error is on top of stack, we'll just nuke input
          # symbol and continue
          lookahead = nil
          next
        end
        t = YaccSymbol.new
        t.type = :error
        # if hasattr(lookahead,"lineno"):
        #    t.lineno = lookahead.lineno
        t.value = lookahead
        lookaheadstack.push(lookahead)
        lookahead = t
      else
        @symstack.pop
        @statestack.pop
        state = @statestack[-1]       # Potential bug fix
      end

      next
    end

    # Call an error function here
    raise RuntimeError.new("yacc: internal parser error!!!")
  end
end