Re: [boost] [local] Help for the Alternatives section

29 Mar 2011


      On 3/29/2011 12:37 AM, lcaminiti wrote:
...
This worked :)) Finally Boost.Local's Phoenix example reads:
#include<boost/spirit/include/phoenix.hpp>
#include
#include
#include
int main() {
     double sum = 0.0;
     int factor = 10;
std::vector v(3);
     v[0] = 1.0; v[1] = 2.0; v[2] = 3.0;
// Passed as template parameter and also defined at expression level.
     std::for_each(v.begin(), v.end(), boost::phoenix::let(
             // Bind `factor` by constant (reference).
             boost::phoenix::local_names::_f = boost::phoenix::cref(factor))[
         // Unfortunately, body cannot use C++ statement syntax.
         // Access `sum` by (non-constant) reference.
         boost::phoenix::ref(sum) += boost::phoenix::local_names::_f *
                 boost::phoenix::arg_names::_1,
         std::cout<<  boost::phoenix::val("Summed: ")<<
                 boost::phoenix::ref(sum)<<  "\n"
     ]);
std::cout<<  sum<<  std::endl;
     return 0;
}
BTW, this is pretty powerful stuff ;)
I'd use using declarations to avoid code clutter and make the
code more readable.

int main() {
     double sum = 0.0;
     int factor = 10;

     std::vector v(3);
     v[0] = 1.0; v[1] = 2.0; v[2] = 3.0;

     using boost::phoenix::let;
     using boost::phoenix::local_names::_f;
     using boost::phoenix::cref;
     using boost::phoenix::ref;
     using boost::phoenix::arg_names::_1;
     using boost::phoenix::val;

     // Passed as template parameter and also defined at expression level.
     std::for_each(v.begin(), v.end(), let(
             // Bind `factor` by constant (reference).
             _f = cref(factor))[
         // Unfortunately, body cannot use C++ statement syntax.
         // Access `sum` by (non-constant) reference.
         ref(sum) += _f * _1,
         std::cout << val("Summed: ") << ref(sum) << "\n"
     ]);

     std::cout << sum << std::endl;
     return 0;
}


Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://boost-spirit.com