Could I have an example of using Continuations as 'co-routines'?

[Asfand Yar Qazi]

Hi,

I've been hanging around on the irc channel recently, getting advice to
reimplement my incomplete C++ game engine in Ruby (I've redone about 2
weeks work in 2 days!)

Here's my problem: instead of using setjmp/longjmp to script my game's
story-line (scripting in C++, tut-tut, what was I thinking?!), I
obviously want to use a Ruby feature, and I assume Continuations are the
thing to do it.

But I don't understand how! My mind is just going upside-down (perhaps
I need to give coding a break for a day or two...)

Anyway, could I have a simple example to start with?

Thanks,
Asfand Yar

 

[Gennady]

Hi,

I've been hanging around on the irc channel recently, getting advice
to reimplement my incomplete C++ game engine in Ruby (I've redone
about 2 weeks work in 2 days!)

Here's my problem: instead of using setjmp/longjmp to script my game's
story-line (scripting in C++, tut-tut, what was I thinking?!), I
obviously want to use a Ruby feature, and I assume Continuations are
the thing to do it.

But I don't understand how! My mind is just going upside-down
(perhaps I need to give coding a break for a day or two...)

Anyway, could I have a simple example to start with?

I hope this will help:
http://www.eleves.ens.fr/home/madore/computers/callcc.html

Also the Pickaxe has some basic examples (you may have seen them
already, though):
http://www.ruby-doc.org/docs/ProgrammingRuby/html/
ref_c_continuation.html

Sincerely,
Gennady Bystritsky

 

[Florian Gross]

Hi,
Moin!

Here's my problem: instead of using setjmp/longjmp to script my game's
story-line (scripting in C++, tut-tut, what was I thinking?!), I
obviously want to use a Ruby feature, and I assume Continuations are the
thing to do it.

Anyway, could I have a simple example to start with?

I did this short snipped which implements a simpler interface for
Continuations to stop them from causing so much headaches for me:

def Continuation.create(*args, &block)
args = [args] if not args.nil? and not args.is_a? Array

cc = nil
result = callcc {|c| cc = c; block.call(cc) if block and args.empty?}

result ||= args
return *[cc, *result]
end

Here's a simple example of a program counting from 1 to 5 using
Continuations:

continuation, number = Continuation.create(1)
if number <= 5
puts number
continuation.call(number + 1)
end

And here's one showing how Continuations could be used for coroutines.
However, as you may have noticed, this is quite clumsy because lots of
repetitive code passages -- even if they can be factored out into
something reusable I would probably still be uncertain about using
Continuations for Coroutines:

def give_numbers
@continuation.call(true) if @continuation

@continuation, done = Continuation.create(false)
return 1 unless done

@continuation, done = Continuation.create(false)
return 2 unless done

@continuation, done = Continuation.create(false)
return 3 unless done

@continuation = nil
return 4
end

give_numbers # => 1
give_numbers # => 2
give_numbers # => 3
give_numbers # => 4
give_numbers # => 1

Thanks,
Asfand Yar

Regards,
Florian Gross

 

[Asfand Yar Qazi]

Asfand Yar Qazi wrote:


And here's one showing how Continuations could be used for coroutines.
However, as you may have noticed, this is quite clumsy because lots of
repetitive code passages -- even if they can be factored out into
something reusable I would probably still be uncertain about using
Continuations for Coroutines:

What do you suggest I use as a coroutine in Ruby, then?