shunsuke wrote:
Joel de Guzman wrote:
I think you misunderstood some of my previous posts. value_of is only used to compute the desired result. There is actually no corresponding value_of function. It is only a metafunction, unlike /at/ which has both a result_of metafunction and a function. When the input sequence is actually traversed to generate the result, /at/ is the one being called. Hence, the sequence above is what is actually generated by as_vector.
It's unfortunate and a bit unintuitive to be using the result_of scheme to compute the value_at metafunction here. MPL uses the nested "apply" for this purpose. OTOH, it would be annoying to have to use "apply" for value_at and "result" for /at/. It's a compromise.
I might probably understand this problem.
transform_view, in order to implement `deref` etc, uses `result_of` in the standard manner, where `result<F(int)> means that rvalue is passed.
Correction: result<F(int&)> which means lvalue is passed. The lvalue is correctly propagated through the transform.
But, as_vector applied to transform_view uses `result_of` in a strange manner through value_of.
A FunctionObject for transform_view requires two result_of implementations; It seems impossible.
I provided an example, didn't I? Actually, there's another way to do it -- take a look at how fusion zip does it. Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net