Re: How to avoid complex switches?

I have a class that takes a few template parameters:

template<typename A, typename B, typename C,typename D>
class MyClass {
// ...
};

The types A,B,C and D are selected from a user specified input file
(properties file):

A = 1
B = 2
C = 1
D = 3

I then parse this file an need to create MyClass with the correct types:

void createMyClass (int a, int b, int c, int d) {

    switch ( a ) {
      case 1 :
        typedef test::Green ColorType;
        switch ( b ) {
          case 1 :
            typedef test::Water MediumType;
            switch ( c ) {
              case 1 :
                typedef test::Linear InterpolationType;
                MyClass<ColorTyper, MediumType, InterpolationType >
myClass;
                break;
              case 2 :
                typedef test::Cubic InterpolationType;
                MyClass<ColorTyper, MediumType, InterpolationType >
myClass;
                break;
              default :
            }
            break;
          case 2 :
            // ....

            break;
          default :
        }
        break;
      case 2 :
        typedef test::Blue ColorType;
        switch ( b ) {
          case 1 :
            typedef test::Water MediumType;
            switch ( c ) {
              case 1 :
                typedef test::Linear InterpolationType;
                MyClass<ColorTyper, MediumType, InterpolationType >
myClass;
                break;
              case 2 :
                typedef test::Cubic InterpolationType;
                MyClass<ColorTyper, MediumType, InterpolationType >
myClass;
                break;
              default :
            }
            break;
          case 2 :

            break;
          default :
        }

        break;
      default :

    }

}

But this switch grows extremely large when the number of choices for
each type grows and is also very ugly/error prone. It could be nice if
it was possible to do something like this instead:

T getAType(int a) {
  switch ( a ) {
    case 1 :
      typedef test::Green ColorType;
      break;
    case 2 :
      typedef test::Blue ColorType;
      break;
    default :
  }
  return ColorType;
}

T getBType(int b) {
  switch ( b ) {
    case 1 :
      typedef test::Water MediumType;
      break;
    case 2 :
      typedef test::Rock MediumType;
      break;
    default :
  }
  return MediumType;
}

int main(){

 typedef getAType(1) ColorType;
 typedef getBType(2) MediumType;
 ...

 MyClass<ColorType, MediumType, ...>
}

But this is not supported in C++. Any ideas on how to solve this
combinatorics problem?