Re: [Boost-users] [Preprocessor] Auitomatic switch generation for template class instanciation

Subject: Re: [Boost-users] [Preprocessor] Auitomatic switch generation for template class instanciation
From: Manfred Doudar (manfred.doudar_at_[hidden])
Date: 2008-11-23 11:35:14

Hello Oliver,

See inline below..

On Sun, 23 Nov 2008 15:31:12 +0100
"Olivier Tournaire" <olitour_at_[hidden]> wrote:

> 
>     switch(priorType)
>     {
>         case 0:
>         switch(dataType)
>         {
>             case 0:
>             {
>             MyModel<MyPriorEnergy,MyDataEnergy> aModel;
>             aModel.SetInput(...);
>             aModel.Optimize(...);
>             }
>             break;
>             case 1:
>             {
>             MyModel<MyPriorEnergy,AnotherDataEnergy> aModel;
>             aModel.SetInput(...);
>             aModel.Optimize(...);
>             }
>             break;
>             default:
>             break;
>         }
>         case 1:
>         switch(dataType)
>         {
>             case 0:
>             {
>             MyModel<MyPriorEnergy,MyDataEnergy> aModel;
>             aModel.SetInput(...);
>             aModel.Optimize(...);
>             }
>             break;
>             case 1:
>             {
>             MyModel<MyPriorEnergy,AnotherDataEnergy> aModel;
>             aModel.SetInput(...);
>             aModel.Optimize(...);
>             }
>             break;
>             default:
>             break;
>         }
>         default:
>         break;
>     }
> 
> I would like to know if there is a way to automate the above switch
> generation. As I have 5 templates, and not only 2, this will really
> helps ... I tried using BOOST_PP_SEQ_FOR_EACH but did not came to a
> result. Then, there is a lot of duplication in the above code. Am I
> doing the right way ?
> 

Looks like an awful lot of repetition, and would have to take a closer
look at your problem for advice on design.  However, to get you going,
below is the Boost.PP work to do what you want - but think even that
could be done better..

#include <boost/preprocessor/repetition/repeat.hpp>
#include <boost/preprocessor/seq/for_each_i.hpp>

#define ECKY(r, data, i, elem)                                 \
              case i:                                          \
              {                                                \
                  MyModel<MyPriorEnergy, elem> aModel;         \
                  aModel.SetInput(...);                        \
                  aModel.Optimize(...);                        \
              }                                                \
              break;
/**/

#define BAR(z, n, text)                                        \
              case n:                                          \
              swtich(dataType)                                 \
              {                                                \
                  BOOST_PP_SEQ_FOR_EACH_I(ECKY, n, text)       \
                  default:                                     \
                  break;                                       \
              }
/**/

#define FOO(n, seq)                                            \
             switch(priorType)                                 \
             {                                                 \
                 BOOST_PP_REPEAT(n, BAR, seq)                  \
                 default:                                      \
                 break;                                        \
             }

FOO(2, (MyDataEnergy)(AnotherDataEnergy))

Cheers,
-- 
Manfred
24 November, 2008