Re: [boost] more problem with functional + projection_iterator

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-10-10 14:04:24

Hi Peter,

Could you please elaborate on this post? I'm very interested in what you're
saying here, but I don't understand any of it!

-Dave

----- Original Message -----
From: "Peter Dimov" <pdimov_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, October 10, 2001 2:05 PM
Subject: Re: [boost] more problem with functional + projection_iterator

> From: "Jeremy Siek" <jsiek_at_[hidden]>
> > P.S. Perhaps we can start thinking about a better model for
> > adaptable function objects.
>
> Yes, perhaps we should.
>
> The whole thing boils down to:
>
> 1. There is no 'adaptable function object' model that can work given the
> current C++:
>
> struct X
> {
>     template<class T> T * operator()(T &);
> };
>
> or, actually, there is, but it's not worth pursuing. :-)
>
> 2. There are two problems that need to be solved, and we'll be able to
> handle arbitrary function objects without needing a model.
>
> 2a. Arbitrary function argument forwarding.
>
> template<class T> void f(T & t);
>
> is close, but not enough.
>
> 2b. Return type inference.
>
> typeof. Enough said.
>
> The various lambda libraries (notably the Lambda library) approximate this
> functionality very well in (current) C++, but they can't solve the problem
> in general. Even _1 << _2 is so disproportionately non-trivial.
>
> --
> Peter Dimov
> Multi Media Ltd.
>
>
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