Re: [Boost-users] [fusion] deduce type of resulting vector from a transformation

On Oct 10, 3:17 am, Christopher Schmidt wrote:

Am 10.10.2010 12:02, schrieb alfC:

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Hi,

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 (I keep struggling with Boos.Fusion.)

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 How do I deduce the type of the vector resulting from the transformation of another vector?

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I have a source vector of different types, e.g. vectorsi::length, quantitysi::mass,    quantitysi::time

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and I have a transformation that is well defined and returns another type depending on the original type. The question is how do I generate a vector type that is the result of the given transformation. I though that result_of::transform was the function to obtain the result but it turns not because it returns a type transform_view instead of a vector.

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vector< ... > v1; T? v2(transform(v1, transformation()));

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i.e. what is the type of T as a fusion::vector as deduced from the type of v1 and the transformation type? -- Thank you,    Alfredo--

You can generate a vector from an arbitrary fusion sequence using the conversion metafunction:

http://www.boost.org/doc/libs/1_44_0/libs/fusion/doc/html/fusion/cont...

fusion::result_of::as_vector<         fusion::result_of::transform<                 v1,                 transformation         >::type

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::type v2(fusion::transform(v1, transformation()));

Hi, thank you. I tried something like this but I keep getting an error from the compiler. /usr/include/boost/utility/result_of.hpp:68: error: invalid use of incomplete type ‘struct divide::result{ typedef typename divide_typeof_helpersi::time >::type type; }; template<typename Q> typename result::type operator()(Q const& q) const { return q/quantitysi::time(1.*si::second); } }; It works well as a function but not as a metafunction in the following typedef typedef boost::fusion::result_of::as_vector< boost::fusion::result_of::transform< source_type, divide >::type >::type result_type ;