Re: [boost] Standard interface for adaptable function objects?

From: David Abrahams (dave_at_[hidden])
Date: 2002-11-22 07:21:26

Anthony Williams <anthony.williamsNOSPAM_at_[hidden]> writes:

> David Abrahams writes:
>  > 
>  > Do we have any precedent for ways to find out what the arity and
>  > argument types of an arbitrary function object is (I'm not talking
>  > about function pointers, here, but "functors")?
>
> Given that a functor might support more than one argument set, the only way I
> can think of is to say "do you support this argument set?" rather than "what
> argument set do you accept?"; in which case you can use the mechanism
> implemented in boost.lambda, and in my function composition library, to deduce
> the return type --- have a member template that takes a typelist representing the
> arguments you wish to pass, and returns the corresponding return type where
> that argument set is valid, or something else (such as invalid_argument_set)
> where it isn't (assuming you want to do something else in the case where it
> isn't, rather than just abort compilation)
>
> Does this give you what you want?

No, the inputs are fully-polymorphic Python objects. If I knew what
"arguments I wish to pass", I'd be all set. I'm only interested in the
cases where that's deducible from the function object. For the other
cases, the user can pass me a type sequence directly.

Thanks anyway.

-- 
                       David Abrahams
   dave_at_[hidden] * http://www.boost-consulting.com
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