Re: [Boost-users] operator<< for std::vector< boost::variant< type_a, type_b >>

Subject: Re: [Boost-users] operator<< for std::vector< boost::variant< type_a, type_b >>
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2018-06-18 19:51:35

On Mon, Jun 18, 2018 at 2:55 PM, Maarten Verhage via Boost-users
<boost-users_at_[hidden]> wrote:
> Dear boost-savvy people,
>
> I fail to understand how I need to write a working ostream overload for a
> type I have.  I've read the boost::variant documentation. As well as
> stackoverflow question:

Not really a Boost question, per se:

See "Stream extraction and insertion" in:

http://en.cppreference.com/w/cpp/language/operators

Basically, you need the stream reference as the first parameter,
followed by whatever it is you are inserting, etc. Remember to return
the stream reference.

After that, decompose as needed for the complexity of your subject.

> https://stackoverflow.com/questions/46343138/using-stdvectorboostvariant-with-google-mock-causes-a-compilation-err
>
> Still I fail to understand how to make it work for the type I have. In the
> code you can see parameter_t is an element in the employee_t. I need to keep
> this data structure this way.
>
> Attached is my single 30 line problem code. I do compile with gcc 5.1.0 with
> C++14 support.
>
> It doesn't compile. The important part of the compiler output might be:
> C:\dev\boost_1_67_0/boost/variant/detail/variant_io.hpp:64:14: error: no
> match for 'operator<<' (operand types are 'std::basic_ostream<char>' and
> 'const std::vector<boost::variant<int, double> >')
>          out_ << operand;
>
> My overload is obviously wrong. I would be very happy if someone can show me
> how to make it work.
>
> Best regards,
> Maarten Verhage
>
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