Errors compiling a piece of fusion with phoenix. Pheonix bug?

[joe@…]

Hi,

I've implemented a dot product of two fusion vectors as a phoenix 2 functor. However it doesn't compile and dies deep inside of phoenix. Is this a bug, or a misunderstanding on my part?

Thanks, Joe

[joe@…]

Source

[joe@…]

Compilation output.

[Joel de Guzman]

I suggest you use Phoenix-3 instead. See Ticket #5480. I am confident that this is no longer an issue. Please do so and tell us your experience so we can close both tickets. If it is still a problem, then let's move this tickets to Phoenix.

[Thomas Heller]

This testcase is working with V3 (minor modifications for the nested result template needed)

[joe@…]

What are those minor modifications?

Can you tell me what's wrong with this please? (It works for pheonix 2)

	template <typename V1, typename V2>
	struct result
	{
		// Presume that the return type is the type of the first element
		// of the first sequence argument.
		typedef typename boost::fusion::result_of::value_at<V1, boost::mpl::int_<0> >::type type;
	};

[joe@…]

For the record

​https://svn.boost.org/svn/boost/trunk/libs/phoenix/example/function.cpp is wrong then?

linked to from the lazy function docs

​https://svn.boost.org/svn/boost/trunk/libs/phoenix/doc/html/phoenix/starter_kit/lazy_functions.html

It's wrong then? :)

[joe@…]

Still trying to get this result struct working. What's wrong with this then?

struct vector_dot_product_impl {
	template<typename V1, typename V2>
	struct result;

	template <typename This, typename V1, typename V2>
	struct result<This(V1, V2)>
	{
		// Presume that the return type is the type of the first element
		// of the first sequence argument.
		typedef typename boost::fusion::result_of::value_at<V1, boost::mpl::int_<0> >::type type;
	};

	template <typename V1, typename V2>
	typename result<V1, V2>::type operator()(V1 v1, V2 v2) const
	{
		using boost::phoenix::arg_names::_1;
		using boost::phoenix::arg_names::_2;
		using boost::fusion::fold;
		using boost::fusion::transform;
		return fold(transform(v1, v2, _1 * _2), 0.0, _1 + _2);
	}
};

Thanks!

[anonymous]

It's ok. I've sussed it out. It has to be

        template<typename Sig>
        struct result;

not

        template<typename V1, typename V2>
        struct result;
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