Larry Evans wrote:
On 12/23/2004 11:16 AM, David Abrahams wrote: [snip]
Another is that (unless you use nonstandard language extensions) only flat structures allow O(1) random access.
I'm afraid I don't understand. By "access" do you mean access to the elements in the structure?
Yes, at compile-time.
If so, then I don't understand why:
r.factor<TypeMap,Index>::my_field
where r is the tuple and Index is the field number (or the superclass number), is not O(1) access. Could you explain why?
I have never seen a tuple type with a nested factor template, so no, I guess I can't.
BTW, if the method used in sum is slightly changed (replace max with + when calculating max_size), then the storage can all be moved to the most derived class and all superclasses just contain functions; hence, the padding problem (I guess) is not longer there. This, of course, is at the cost of a little more complicated product::project method.
I guess you're assuming I've looked at your code again ;-) -- Dave Abrahams Boost Consulting http://www.boost-consulting.com