I have a program which looks like this
// tuple example
#include <iostream> // std::cout
#include <tuple> // std::tuple, std::get, std::tie, std::ignore
using namespace std;
template <int i> class xEnum
{
public:
enum val
{
x1,
x2
};
};
template <> class xEnum<0>
{
public:
enum val
{
RED,
GREEN,
WHITE
};
};
template <> class xEnum<1>
{
public:
enum val
{
BANANA,
ORANGE,
APPLE
};
};
class color:public xEnum<0>
{
public:
static tuple<int, int, int> var;
template< xEnum<0>::val i > static auto getVal()
{
return get<i>( var );
}
};
tuple<int, int, int> color::var(10, 11, 12);
class fruit:public xEnum<1>
{
public:
static tuple<int, int, int> var;
template< xEnum<1>::val i > static auto getVal()
{
return get<i>( var );
}
};
tuple<int, int, int> fruit::var(20, 21, 22);
template <int index> class variable:public xEnum<index>
{
public:
static tuple<int, int, int> var;
template< xEnum<index>::val i > static auto getVal()
{
return get<i>( var );
}
};
int main ()
{
cout<<"Value is "<<color::getVal<color::RED>()<<endl;
cout<<"Value is "<<color::getVal<color::GREEN>()<<endl;
cout<<"Value is "<<color::getVal<color::WHITE>()<<endl;
cout<<"Value is "<<fruit::getVal<fruit::BANANA>()<<endl;
cout<<"Value is "<<fruit::getVal<fruit::ORANGE>()<<endl;
cout<<"Value is "<<fruit::getVal<fruit::APPLE>()<<endl;
return 0;
}
This program compiles without any issues. Output of the program is
$ g++ -Os -std=c++1y prog.cpp
$ ./a.exe
Value is 10
Value is 11
Value is 12
Value is 20
Value is 21
Value is 22
Looking at the class color and fruit shows that they have a similar pattern. So I tried putting a generic class in place of the two classes, which looked like below
template <int index> class variable:public xEnum<index>
{
public:
static tuple<int, int, int> var;
template< xEnum<index>::val i > static auto getVal()
{
return get<i>( var );
}
};
But with above template class I get compiler error below:
error: 'xEnum::val' is not a type
template< xEnum<index>::val i > static auto getVal()
Could someone please suggest a way to get rid of this compiler error or a way to define the two classes fruit and color in a generic way?
Thanks in advance.
Only way I could come up with is
#define var_class(x, y) class x:public xEnum<y> \
{ \
public: \
static tuple<int, int, int> var; \
template< xEnum<y>::val i > static auto getVal() \
{ \
return get<i>( var ); \
} \
}\
Above macro works, but I am not too keen on using macros to avoid repetition of code in c++. There should be some elegant c++ template solution to avoid this.
