Class: Cyc::Parser

Inherits:
Object
  • Object
show all
Defined in:
lib/cyc/parser.rb

Overview

Author

Aleksander Pohl ([email protected])

License

MIT/X11 License

The class used to parse the answer of the Cyc server.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Parser

Returns a new instance of Parser.



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# File 'lib/cyc/parser.rb', line 7

def initialize
  @lexer = SExpressionLexer.new
end

Instance Method Details

#parse(message, stack = nil) ⇒ Object

Parses message received from server. Accepts message to parse and a stack with a partial parse result.



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# File 'lib/cyc/parser.rb', line 13

def parse(message,stack=nil)
  @lexer.scan_str(message)
  stack ||= [[]]
  while !(token = @lexer.next_token).nil?
    #p token
    case token[0]
    when :open_par
      stack.push []
    when :close_par
      top = stack.pop
      stack[-1].push top
    when :atom
      if token[1] == "T"
        stack[-1] << true
      else
        # FIXME find way to differentiate strings and atoms
        stack[-1] << token[1]
      end
    when :cyc_symbol
      stack[-1] << ::Cyc::Symbol.new(token[1][1..-1])
    when :variable
      stack[-1] << ::Cyc::Variable.new(token[1][1..-1])
    when :term
      stack[-1] << token[1][2..-1].to_sym
    when :string
      stack[-1] << token[1]
    when :open_as
      stack.push [:as]
    when :close_quote
      top = stack.pop
      if top[0] == :as
        as = Assertion.new(top[1],top[2])
        stack[-1].push as
      else
        stack.push top
      end
    when :continuation
      top = stack.pop
      stack[-1].push top
      raise ContinueParsing.new(stack[0][0])
    when :nil
      stack[-1] << nil
    when :assertion_sep
      # ignore
    end
  end
  stack[0][0]
rescue ContinueParsing => ex
  raise
rescue Exception => ex
  raise ParserError.new("Exception #{ex} occurred when parsing message '#{message}'.")
end