As pointed out by John, another advantage of compile-time access is the ability to have different types for each coordinate. It's something that has been asked for several times during recent discussions on this list. I was even wondering the other day if it wouldn't be better to not require any coordinate_type typedef and have the algorithms deducing by themselves the type of each coordinate by a BOOST_TYPEOF on the accessor.
Can you provide me with a code example of how to do this? I'm getting really tired of writing typename point_traits<T>::coordinate_type over and over and over again. I would greatly appreciate a better way.
You can have the type of a coordinate by applying BOOST_TYPEOF on the expression by which you access this coordinate. For instance, let's say we have a tuple<float,double> t: BOOST_TYPEOF(t.get<0>()) x = t.get<0>(); BOOST_TYPEOF(t.get<1>()) y = t.get<1>(); x will be a float and y will be a double. Here you can see that we ended up writing "t.get<0>()" and "t.get<1>()" twice, once for the declaration and once for the initialization. BOOST_AUTO can help by both declaring and assigning at the same time: BOOST_AUTO(x, t.get<0>()); BOOST_AUTO(y, t.get<1>()); x is a float and receives the value of t.get<0>(), y is a double and receives the value of t.get<1>(). Bruno