continuations and clone problem

[Simon Strandgaard]

This class should convert internal-iterators to external-iterators.
But how do I clone them?

Any advice are deeply appreciated.

--
Simon Strandgaard




server> ruby a.rb
a.rb:28:in `next': undefined method `call' for false:FalseClass (NoMethodError)
from a.rb:28:in `callcc'
from a.rb:28:in `next'
from a.rb:43
server> expand -t2 a.rb
class Object
def deep_clone
Marshal::load(Marshal.dump(self))
end
end

class IteratorContinuation
def initialize(instance, symbol)
@instance = instance
@symbol = symbol
first
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
callcc{|@return_where| @resume_where.call }
end
def is_done?
@resume_where == false
end
def current
@value
end
end

i1 = IteratorContinuation.new("hello world", :each_byte)
i1.next
i1.next
i1.next
i2 = i1.clone # deep_clone not possible
i2.next
p i1.current
p i2.current
server>

 

[ts]

Try this (not tested)

S> class IteratorContinuation

def marshal_dump
[@instance, @symbol]
end

def marshal_load(arr)
initialize(*arr)
end

S> end

S> i1 = IteratorContinuation.new("hello world", :each_byte)
S> i1.next
S> i1.next
S> i1.next
S> i2 = i1.clone # deep_clone not possible

i2 = i1.deep_clone

S> i2.next
S> p i1.current
S> p i2.current



Guy Decoux

 

[Simon Strandgaard]

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>