Re: [Boost-users] compile-time mapping: a[1] --> a1 ?

7 Sep 2005


      "Steven Allmaras" <steven.r.allmaras@boeing.com> wrote
...
I would like to do a compile-time mapping of an array accessor to a list
of
scalars as in the following class:
class MyArray1 {
  public:
  double& operator[](int n) { ??? }
private:
  double a0, a1, a2, a3 ;
} ;
int main() {
  MyArray1 x ;
x[1] = 2. ;
}
How about something like this:

#include <boost/preprocessor/repeat.hpp>
#include <boost/preprocessor/enum_params.hpp>
#include <boost/mpl/int.hpp>
#include <iostream>

using namespace std;

#define DEFINE_FUNC(z, n, _)\
    double& operator[](boost::mpl::int_<n>)\
    {\
        return a ## n;\
    }

#define DEFINE_ARRAY(Name, n)\
    class Name\
    {\
    public:\
        BOOST_PP_REPEAT(n, DEFINE_FUNC, ~)\
    private:\
        double BOOST_PP_ENUM_PARAMS(4, a);\
    };

DEFINE_ARRAY(MyArray1, 4)

int main()
{
  MyArray1 x;

  x[boost::mpl::int_<0>()] = 2.;
  x[boost::mpl::int_<3>()] = 5.;
  // x[boost::mpl::int_<4>()] = 7.; // compile error

  cout << x[boost::mpl::int_<0>()] << endl;
  cout << x[boost::mpl::int_<3>()] << endl;
}

Regards,
Arkadiy

Re: [Boost-users] compile-time mapping: a[1] --> a1 ?

Arkadiy Vertleyb