Class: Fabulator::Grammar::Expr::Rule

Inherits:
Object
  • Object
show all
Defined in:
lib/fabulator/grammar/expr/rule.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Rule

Returns a new instance of Rule.



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# File 'lib/fabulator/grammar/expr/rule.rb', line 7

def initialize
  @alternatives = [ ]
end

Instance Attribute Details

#name ⇒ Object

Returns the value of attribute name.



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# File 'lib/fabulator/grammar/expr/rule.rb', line 5

def name
  @name
end

Instance Method Details

#add_alternative(a) ⇒ Object 



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# File 'lib/fabulator/grammar/expr/rule.rb', line 11

def add_alternative(a)
  @alternatives << a
end

#parse(s) ⇒ Object

Raises:



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# File 'lib/fabulator/grammar/expr/rule.rb', line 15

def parse(s)
  if s.anchored
    @alternatives.each do |alternative|
      ret = s.attempt { |cursor| 
        cursor.anchored = true 
        alternative.parse(cursor) 
      }
      if !ret.nil?
        s.set_result(ret)
        return
      end
    end
  else
    while !s.eof?
      start = s.pos
      @alternatives.each do |alternative|
        ret = s.attempt { |cursor| 
          cursor.anchored = true 
          alternative.parse(cursor) 
        }
        if !ret.nil?
          s.start = start
          s.set_result(ret)
          return
        end
      end
      s.advance_position(1)
    end
  end
  raise Fabulator::Grammar::RejectParse
end