Re: [boost] [range] concept checks break chained range adaptors

Subject: Re: [boost] [range] concept checks break chained range adaptors
From: Sergey Mitsyn (svm_at_[hidden])
Date: 2014-06-15 05:20:58

Hello,

 > std::vector<std::string> separated
> std::set<Foo> foos;
>
> boost::copy(separated |
>                  boost::adaptors::transformed(boost::bind(Foo::fromString, _1))
> |
>                  boost::adaptors::filtered(boost::bind(&Foo::isValid, _1)),
>                  std::inserter(foos, foos.end()));
>

boost::copy forwards everything to std::copy with iterators that hold 
function objects by value. Iterator concept requires iterators to be 
default constructible, but if they hold function objects that have 
binded data they cannot be made such.

FWIW one of solutions to this problem is wrapping function object f with 
boost::regular(f), available here:

https://github.com/faithandbrave/OvenToBoost

AFAIR it's supposed to be integrated into boost some day, and also there 
was some discussion in this list about it.

-- 
------------
Sergey Mitsyn.