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

On 5/30/10 11:26 AM, alfC wrote:

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I am not sure if this is the best way to do it in either Lambda nor Phoenix (I'm pretty sure that even with lambda, you are going beyond the documentation, no?).

I guess that extracting subexpressions (and subexpression types) of an expression goes beyond Lambda and Phoenix documentation. and yes that is what I am trying to do.

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However, I am not knowledgeable enough of the domain you are involved with, nor do I know what qawc means.

qawc is an interface to http://tinyurl.com/gslqwac now you can imagine what I a trying to do, basically extract the function information from a lambda expression.

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In Phoenix (see Actors In Detail at:http://tinyurl.com/24wlduz), a lambda is always an:

actor<Eval> The documented "result" protocol for Eval is:

T::result<Env>::type

where Env is your environment (See the link I provided above). Typically, for client use, the environment is just basic_environment<...>.

well I tried this and didn't work typename actor<LambdaExp>::result

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::type

now my closest guess is typename actor<LambdaExp>::template result::type

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? Anyway, I think I need to look more closely. But right now, I'm quite full. It seems you have it working anyway, no? 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. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net