Re: [Boost-users] [fusion] const and transform algorithm

----- Original Message ----- From: "Joel de Guzman" To: Sent: Wednesday, January 07, 2009 1:58 AM Subject: Re: [Boost-users] [fusion] const and transform algorithm

vicente.botet wrote:

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----- Original Message ----- From: "Joel de Guzman" To: Sent: Tuesday, January 06, 2009 11:26 PM Subject: Re: [Boost-users] [fusion] const and transform algorithm

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vicente.botet wrote:

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Hi,

What is the reason fusion::transform taskes a const Sequence? template< typename Sequence, typename F

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typename result_of::transform::type transform( Sequence const& seq, F f);

Does this means that the transform do not change the sequence itself o also its elements? Yes. Fusion transform returns a lazy (transform) view. This view is non-mutating. It is not like STL's transform which mutates the target container in place. Fusion's is purely functional and lazily evaluated.

Can for_each mutate the sequence elements?

Yes.

if yes, would the following get a

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transformation I'm locking for?

I don't know. I'm not sure what you are looking for.

I just wat to apply the unction get to a tuple of futures and reviver the stored values. T& future<T>::get() is non const

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vector v; v = transform(v, f);

I was lock for in the documentation and I have not found this assignation. Where in the documentation can I found that I can do that?

See the sequence/views concepts and the docs for the containers. For example (http://tinyurl.com/84vdvp):

Notation: v Instance of vector s A Forward Sequence

Expression Semantics: v = s Assigns to a vector, v, from a Forward Sequence, s.

Thanks for the reference. I was looking for a function prototype. BTW, the example is not in line with the functions. vector v(12, 5.5f); std::cout << at_c<0>(v) << std::endl; std::cout << at_c<1>(v) << std::endl;

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If for_each can change/mutate the sequence itself, why don't have a mutating_transform that takes a Sequence& and not a Sequence const&

Because it is not needed.

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Just a last question. How move semantics maps with purely functional Sequences? Do you plan to add move semantics for the elements of the tuple? The concept of MovableSequence has a sens for you?

Makes sense. Last BoostCon, we had a workshop about implementing Fusion for 0x incuding move. We'll have it when it is available.

Great! Would you try with a Boost.Move library? Thanks, Vicente