I paste a snippet to show how it works.
Everyone who has studied the book Think in C++ 2nd Edition knows the sample, trash collection, which is at the end of chapter 10, Design pattern.
Ok, let´s begin with this.
the sample mentioned in Think in C++ using double dispatch to implement the design. and I use Generic Programming method to do the same thing.
Enjoy.
#include<vector>
#include <iostream>
using namespace std;
class Trash
{
};
class Paperbin;
class Glassbin;
class Paper:public Trash
{
public:
typedef Paperbin aBin;
};
class Glass:public Trash
{
public:
typedef Glassbin aBin;
};
class Paperbin:public vector<Paper>
{
};
class Glassbin:public vector<Glass>
{
};
template<int v>
struct Int2Type
{
enum{value=v};
};
template<class T, class U>
class Conversion
{
typedef char Small;
struct Big {char dummy[2];
};
static Small Test(U);
static Big Test(...);
static T MakeT();
public:
enum{ exists=(sizeof(Test(MakeT()))==sizeof(Small))};
};
template<class Trashs, class Bin>
Add(Trashs trash, Bin bin)
{
cout<<Conversion<Trashs::aBin ,Bin>::exists<<endl;
_Add(trash,bin,Int2Type<Conversion<Trashs::aBin ,Bin>::exists >());
}
template<class Trash, class Bin>
_Add(Trash trash, Bin bin,Int2Type<true>)
{
bin.push_back(trash);
cout<<"success adding"<<endl;
};
template<class Trash, class Bin>
_Add(Trash trash, Bin bin,Int2Type<false>)
{
cout<<"failed adding"<<endl;
};
int main()
{
Paper apaper;
Glass aglass;
Paperbin apaperbin;
Glassbin aglassbin;
Add(apaper,apaperbin);
Add(aglass,aglassbin);
Add(apaper,aglassbin);
Add(aglass,apaperbin);
return 0;
}
you can reach me by send me a email at bu3bu4@263.net.
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