Re: [Boost-users] [phoenix][lambda] lambda to phoenix translation: get sig (signature) from actor

...

which is almost the type I am trying to generate but it is of 'const&' (const reference) type which is a problem for a return type because of 'returning reference to temporary'.

Perhaps just remove ref if you want the value?

yes, I did that typename remove_reference::type>::type but the syntax is becoming difficult.

Anyway, I think I need to look more closely. But right now, I'm quite full. sorry if I made you waste your time, and thank you for your help so far.

It seems you have it working anyway, no?

yes and no, the argument and the return type are fully translated from lambda to phoenix the final result is: typename remove_reference< typename actor<LambdaExp>::template result::type>::type qawc(actor, boost::phoenix::value< quantity<UnitIntegrandDomain> > > > > > > f_expr, boost::numeric::interval

const& iv ){

Now the problem is to translate the body of the function, the original Boost.Lambda version was bind( &LambdaExp::template sig

::type::value, get<0>(f_expr.args) (bind(&quantity<UnitIntegrandDomain>::from_value, _1)) ), which I can not translate into boost.phoenix, my best try is boost::phoenix::bind( &remove_reference::type>::type::value, actor<LambdaExp>(at_c<0>(f_expr))( boost::phoenix::bind( &quantity<UnitIntegrandDomain>::from_value, boost::phoenix::arg_names::arg1 ) ) ); which does not compile ("no match for call to ‘(actor >) (actor

On one hand Phoenix seems more powerful than BLL but BLL is more intuitive to go into the internal works.

If so, can we get back to this later so I can offer a better library solution? I'm very interested with this and how we can do better with the current Phoenix-3 rewrite.

Sure, glad you are interested. Let me know if you need more details, what I am doing now is an experimental code to interface GSL routines from C++ that uses lambda expression. Experimental in the sense that I want to see how far I can get with Phoenix in terms of building a natural (mathematical) language interface to numerical routines. In this experimental code I am trying to make the functions smart enough to recognize *simple* patterns in the expression. In this example, it recognizes the singularity (at 3.) in the integral integral( f( _1 )/(_1 - 3.) , interval(2., 4.)); other simple expressions are solve( f(_1) == 2.); just to give you an idea. I am not sure if am repeating someone else's work but when I see expression templates in C++ I see numerical and symbolic mathematics converge into the perfect language to do scientific computing. Of course the patterns do not need to be necessarily *simple* in the future, once we master Phoenix we can go beyond to write transformation rules for expression, in order to do that I must gain complete access to the internal subexpressions and subexpression types. Thank you, Alfredo