On 3/21/07, shunsuke <pstade.mb@gmail.com> wrote:
Daniel Walker wrote:
If/when lambda standardizes on result<>, the lambda related special cases in result_of can be removed.
It will break a code using not result_of but sig compatible functors?
Yes. That's the reason lambda would support both for a time with sig<> being deprecated. After a release or two (giving users plenty of time to update their code) sig<> would be removed. This gives them a fair warning and time to adapt.
template<class F, class Arg> void g(F const& f, Arg& x) { typename result_of< F(F, Arg) >::type y = f(x); }
This usage of 'result_of' seems wrong. You meant? typename result_of< F(Arg&) >::type y = f(x);
Thanks for pointing this out. You're right, this is incorrect. I thought this usage was awkward when I first saw it. I just thought it was cool that my lambda changes worked at all and that's largely due to the sound library design of Jaakko Järvi. I'll submit an explanation and a revised lambda patch on the thread where I posted the original.
Can the patch support a sig compatible functor which is "nullary-callable" (e.g. lambda::constructor<>) ?
Yes. I just tested it with lambda::constructor<>, and it does work.
result_of requires a function/functor type.
I really want the type, which can be used with result_of. Some considerations will be required.
Oh, I misunderstood. I thought you wanted the type that result_of generates. Everything regarding types that can be used with result_of is the same as the current result_of documentation with two exceptions. First, where the documentation says "F::result<F(T1, T2, ..., TN)>::type" add 'or F::sig<tuple<F, T1, T2, ..., TN> >::type'. Second, result_of accepts any functor generated by a lambda expression; specifically any type instantiated from lambda::lambda_functor<>. If/when lambda standardizes on result<> instead of sig<> you could remove both exceptions and revert the documentation back to it's current state.
struct functor { BOOST_FIXED_ARITY_FUNCTOR_RESULT(2, A1)
template<class Arg> typename result<functor(functor, Arg)>::type operator()(Arg const& a) const { return a; } };
I introduce <boost/detail/functionN.hpp> at Boost.Accumulators, which seems very cool.
I looked for your file in the boost-sandbox cvs repository and couldn't find it. Could you send a link? Thanks! Daniel