Re: [boost] more problem with functional + projection_iterator

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-10-04 13:29:08

Are you sure you don't want a transform_iterator_adaptor instead?

-Dave

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  David Abrahams, C++ library designer for hire
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          email: david.abrahams_at_[hidden]
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----- Original Message -----
From: "Levente Farkas" <lfarkas_at_[hidden]>
To: "boost" <boost_at_[hidden]>
Sent: Thursday, October 04, 2001 12:25 PM
Subject: [boost] more problem with functional + projection_iterator

> hi,
> I try to compile the attached example and faild both with MSVC 6sp5 and
> gcc-2.96 on linux. the problem is in unary_compose (from compose1). even
if I
> switch from std::compose1 to boost::compose1 the problem exists. the
reason
> is a bit complicated. every function object (subclass of
std::unary_function)
> return with result_type which is usualy not a reference! what's more it
> can't be a reference since everybody suppose these functions are return
> with T& and result_type defined as T. that's the reason why
projection_iterator
> suppose it and put & the place where it's required. IMHO this whole
> thing is a huge design mistake. result_type should have to be defined
> as the real result type of operator(). anyway this would be a better
> choise for argument_type too. solutions (if we don't would like to
> change the whole stl paradigm to right way result_type have to be the
> real result type,...) to change all functionals definition to
> typename call_traits<typename
unary_traits<Operation1>::result_type>::param_type
> in this case all functor can be used as an argumnet for another functor.
> without this this's unsolvable.
> or anybody has any better idea?
>
>  -- Levente                               "Si vis pacem para bellum!"
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