On 19 September 2012 11:04, Igor R wrote:

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i have these 2 functions provided to me and I wonder whether they can somehow be chained without using intermediary memory?

http://codepad.org/tTwkUQhp

No. You have to supply a range [begin..end) for fun2(), so this range should be prepared first.

someone mentioned boost.coroutine could help in this case?

Not with the signatures you specified. If *you* define and implement these templates (i.e. they are not from a 3d party), and you want to adjust their signatures and implementations to make them a generator/coroutine, then maybe it's feasible... http://ok73.ok.funpic.de/boost/libs/coroutine/doc/html/

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i have these 2 functions provided to me and I wonder whether they can somehow be chained without using intermediary memory?

http://codepad.org/tTwkUQhp

No. You have to supply a range [begin..end) for fun2(), so this range should be prepared first.

someone mentioned boost.coroutine could help in this case?

I'm the one who mentioned that, and yes, it is possible :)

Basically, one can use coroutines to implement a generic outputs_of() function that takes a unary function whose argument is an output iterator, and returns a range representing all the values passed to this output iterator, without storing them all.

You would call it like this:

fun2(outputs_of(bind(fun1, input, _1)), output)

I actually wrote such a function, but using an earlier version of the coroutine library (back when the coroutine functionality was still in Boost.Context). I am planning to update my implementation after the interface of Boost.Coroutine is stabilized (it is currently under review on the dev list). I am happy to post it once I've done that

Turns out that the final version of Boost.Coroutine that made it into the 1.53 release has out-of-the-box support for treating the values returned by a coroutine as a range, which makes writing such an outputs_of() function trivial: using boost::coroutines::coroutine; ... template coroutine outputs_of(F f) {     return coroutine{[f](typename coroutine::caller_type& caller)     {         f(boost::make_function_output_iterator([&caller](const T& t){ caller(t); }));     }}; } A complete example using the two functions in your original post is attached. The code uses some C++11 features like lambdas, but these can easily be translated to their C++03 equivalents if necessary. I'll leave it to you as an exercise to do that if you need to. Hope that helps! Regards, Nate

thanks Oliver,Nate, I will deploy this once is 1.54 is released, MM On 19 February 2013 08:05, Oliver Kowalke wrote:

2013/2/18 Nathan Ridge

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Turns out that the final version of Boost.Coroutine that made it into the 1.53 release has out-of-the-box support for treating the values returned by a coroutine as a range, which makes writing such an outputs_of() function trivial:

using boost::coroutines::coroutine; ... template coroutine outputs_of(F f) { return coroutine{[f](typename coroutine::caller_type& caller) { f(boost::make_function_output_iterator([&caller](const T& t){ caller(t); })); }}; }

A complete example using the two functions in your original post is attached.

The code uses some C++11 features like lambdas, but these can easily be translated to their C++03 equivalents if necessary. I'll leave it to you as an exercise to do that if you need to.

Hope that helps!

Regards, Nate

boost.coroutine required some fixes releated C++11 and iterators (thank you nate) - the fixes are applied to trunk and should be available in boost-1.54. Oliver

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