On Sat, Apr 12, 2008 at 8:38 PM, Eric Niebler <eric@boost-consulting.com> wrote:
Eric Niebler wrote:
I recently had a C++ problem and found an answer that tickled my brain. In the spirit of Car Talk on NPR, I thought I'd share it in the form of a puzzler. <snip>
Answer next week, unless someone beats me to it.
Wow, everybody loves a puzzle! This is good fun.
Yup! Great fun.
Giovalli:
Giova*ll*i ?!?!?!
conditional operator. Wish I thought of that. But it requires types to be associated with integers via a global registry, so I can't use it. Is there a way to avoid select() and result<>? It's easy with typeof, but can you do it without?
Here is a try. it probably will look more at home at an obfuscated C++ context. It works up to 5 types. Extending it beyond is a matter of a little of pp metaprogramming. The only O(N) template (that I can see) instantiation is template<class T> default_type::operator T(); And you do not pay for it if you do not use default_type (partially specializing common_type may work as an optimization). I'll try to get rid even of this. Even if there are very few template instantiations, compile time isn't that good. I thought that compile time integral expression computations were basically free. Maybe I'm missing something. -- gpd