Class: Scanner

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

Instance Method Summary collapse

Constructor Details

#initialize(inStream) ⇒ Scanner

Returns a new instance of Scanner.



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# File 'lib/scanner.rb', line 5

def initialize(inStream)
  @istream = inStream
  @keywords = Set.new(["S","R"])
  @lineCount = 1
  @colCount = -1
  @needToken = true
  @lastToken = nil
end

Instance Method Details

#getToken ⇒ Object 



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# File 'lib/scanner.rb', line 18

def getToken()
  if !@needToken then 
    @needToken = true
    return @lastToken
  end
  
  state = 0
  foundOne = false
  c = @istream.getc()
  
  if @istream.eof() then
    @lastToken = Token.new(:eof,@lineCount,@colCount)
    return @lastToken
  end
  
  until foundOne do
    @colCount = @colCount + 1
    case state
    when 0
      lex = ""
      column = @colCount
      line = @lineCount
      if isLetter(c) then state=1
      elsif isDigit(c) then state=2
      elsif c == ?+ then state = 3
      elsif c == ?- then state = 4
      elsif c == ?* then state = 5
      elsif c == ?/ then state = 6
      elsif c == ?( then state = 7
      elsif c == ?) then state = 8
      elsif c == ?\n then 
        @colCount = -1
        @lineCount = @lineCount+1
      elsif isWhiteSpace(c) then state = state #ignore whitespace
      elsif @istream.eof() then
        @foundOne = true
        type = :eof
      else
        puts "Unrecognized Token found at line ",line," and column ",column,"\n"
        raise UnrecognizedTokenException # "Unrecognized Token"
      end
    when 1
      if isLetter(c) or isDigit(c) then state = 1
      else
        if @keywords.include?(lex) then
          foundOne = true
          type = :keyword
        else
          foundOne = true
          type = :identifier
        end
      end
    when 2
      if isDigit(c) then state = 2
      else
        type = :number
        foundOne = true
      end
    when 3
      type = :add
      foundOne = true
    when 4
      type = :sub
      foundOne = true
    when 5
      type = :times
      foundOne = true
    when 6
      type = :divide
      foundOne = true
    when 7
      type = :lparen
      foundOne = true
    when 8
      type = :rparen
      foundOne = true
    end

    if !foundOne then
      lex.concat(c)
      c = @istream.getc()
    end

  end
 
  @istream.ungetc(c)   
  @colCount = @colCount - 1
  if type == :number or type == :identifier or type == :keyword then
    t = LexicalToken.new(type,lex,line,column)
  else
    t = Token.new(type,line,column)
  end

  @lastToken = t
  return t 
end

#putBackToken ⇒ Object 



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# File 'lib/scanner.rb', line 14

def putBackToken()
  @needToken = false
end