RE: optimization question: mpl

["Hite, Christopher" <Christopher.Hite@partner.commerzbank.com>]

> Generally without knowing the compiler version you are using
> it is hard to tell.  
I'll use whatever's best.  Right now I'm still on 4.4.3.  I'll probably
upgrade soon to 4.5.

> The same is true without a complete compilable testcase.
I didn't want to make a test case that depends on boost::mpl. How's
this:

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;
}


> You can use the flatten attribute to tell the compiler to inline all
> calls in a given function, like
> 
> void __attribute__((flatten)) foo(void)
> {
> ...
> decode1();
> ...
> }

That would cause decode1() to be inlined, which might not be what you
want.

Hmm maybe I could rewrite things so the switch case returns a function
pointer.  I'm guessing that would make things slower though.