From: Simon Strandgaard <neoneye@...>
Date: 2003-11-21T20:27:15+09:00
Subject: Re: continuations and clone problem

On Fri, 21 Nov 2003 19:53:47 +0900, ts wrote:
> 
>  Try this (not tested)
> 
>    def marshal_dump
>    def marshal_load(arr)

Above partially solves it. However adding a position count, then it fully
works.   Thanks.


Cloning continuations seems not to be possible ?

irb(main):001:0> x = false
=> false
irb(main):002:0> callcc{|x| }
=> nil
irb(main):003:0> p x
#<Continuation:0x81cba80>
=> nil
irb(main):004:0> y = x.clone
NoMethodError: allocator undefined for Continuation
        from (irb):4:in `clone'
        from (irb):4



Therefore when doing cloning, I must iterate until @position are reached.
Any idea if this skip-until-position code can be reduced?

--
Simon Strandgaard


server> ruby a.rb
"l"
"o"
server> expand -t2 a.rb 
class Object
  def deep_clone
    Marshal::load(Marshal.dump(self))
  end
end

class IteratorContinuation
  def initialize(instance, symbol, position=nil)
    @instance = instance
    @symbol = symbol
    @position = position || 0
    first
    @position.times { self.next }    # TODO:  can this be avoided ?
  end

  def first
    @value = nil
    @resume_where = false
    @return_where = Proc.new{}
    @instance.method(@symbol).call {|i|
      @value = i
      callcc{|@resume_where|
        @return_where.call
        return
      }
    }
    @resume_where = false
    @return_where.call
  end
  def next
    @position += 1
    callcc{|@return_where| @resume_where.call }
  end
  def is_done?
    @resume_where == false
  end
  def current 
    @value
  end
  def clone
    self.class.new(@instance, @symbol, @position)
  end
  def marshal_dump
    [@instance, @symbol, @position]
  end
  def marshal_load(arr)
    initialize(*arr)
  end
end

i1 = IteratorContinuation.new("hello world", :each_byte)
i1.next
i1.next
i1.next
i2 = i1.clone 
#i2 = i1.deep_clone 
i2.next
p i1.current.chr #=> "l"
p i2.current.chr #=> "o"
server>