Re: optimization question: mpl

[Larry Evans]

On 07/28/10 10:53, Hite, Christopher wrote:
[snip]

struct DecodeContext;

struct M1{
        static const int id=1;
        static void decode(DecodeContext& ){}
};

struct M2{
        static const int id=2;
        static void decode(DecodeContext& ){}
};

struct M3{
        static const int id=3;
        static void decode(DecodeContext& ){}
};


template <int> struct ListMember;

template <> struct ListMember<1>{ typedef M1 type; };
template <> struct ListMember<2>{ typedef M2 type; };
template <> struct ListMember<3>{ typedef M3 type; };

template<int i>
void foo(int id, DecodeContext& dc) {
        typedef typename ListMember<i>::type M;
        if(M::id==id)
                M::decode(dc);
        else
                foo<i-1>(id,dc);
}

template<>
void foo<0>(int id, DecodeContext& dc) {}



int main(){
        DecodeContext& dc= *(DecodeContext*)0;// junk for now
        int id=2; //sometime runtime dependent
        foo<3>(id,dc);
        return 0;
}

[snip]
Wouldn't the following simplification work just as well?

template <int Id> struct ListMember{
        static void decode(DecodeContext& ){}
};

template<int i>
void foo(int id, DecodeContext& dc) {
        if(i=id)
                ListMember<i>::decode(dc);
        else
                foo<i-1>(id,dc);
}