Re: [boost] [phoenix] comma woes

Subject: Re: [boost] [phoenix] comma woes
From: Thomas Heller (thom.heller_at_[hidden])
Date: 2011-03-28 11:36:22

On Sunday, March 27, 2011 12:07:04 AM Steven Watanabe wrote:
> AMDG
> 
> I was going to post a response to Lorenzo's question using phoenix,
> but I ran into a few issues.
> 
> The initial version I wrote compiles, but doesn't work.
> 
> #include <boost/phoenix/core.hpp>
> #include <boost/phoenix/operator.hpp>
> #include <iostream>
> #include <vector>
> #include <algorithm>
> 
> int main() {
>      double sum = 0.0;
>      int factor = 10;
> 
>      using namespace boost::phoenix;
>      using namespace boost::phoenix::placeholders;
> 
>      std::vector<double> v(3);
>      v[0] = 1.0; v[1] = 2.0; v[2] = 3.0;
>      std::for_each(v.begin(), v.end(), (
>          ref(sum) += factor * _1,
>          ref(std::cout) << "Summed: " << ref(sum) << std::endl
>      ));
>      return 0;
> }
> 
> This is because the overloaded comma operator
> is provided by statement.hpp, not operator.hpp as
> I had erroneously assumed.  Can we please make
> sure that the built-in comma operator can't
> get silently called?

Thanks for the heads up. I can add the operator, for actor at all times, but 
keep it disabled (with a compile error) untile boost/phoenix/statement.hpp is 
included.
 
> After I added #include <boost/phoenix/statement.hpp>,
> it still doesn't compile and I have no idea how to
> make it compile, because it tries to copy std::cout.
> I'm guessing that the result of the comma operator
> is being deduced as a non-reference, since the
> cout part compiles fine by itself.

Has this issue been resolved now? Looking at the test runner matrix the MSVC10 
runner doesn't have problems like these. Maybe we should add a testcase for that 
...

Regards,
Thomas