Arkadiy Vertleyb wrote:
What is current state of the art on l-value/r-value detection? (I know Eric made some progress in the past by using the "?" operator).
What we have in typeof is quite primitive :-(
I think it might be a good idea to eventially factor it out into a separate header file, and reuse, to avoid contradictions between different libs, and provide the single point of maintenance...
FOREACH does rvalue detection that is able to detect even const-qualified rvalues on highly conforming compilers, but there is a serious limitation to the technique: it doesn't yield a compile-time constant. This means it is not applicable to typeof, sadly. The closest I've been able to come to reliable, compile-time detection of rvalues in standard C++ is to see if the expression can be bound to a reference. Naturally, this is foiled by const-qualified rvalues. I think that's what you're already doing in typeof, right? It's an open question whether it's possible to do this in standard C++. If it's possible, I'd be very interested. -- Eric Niebler Boost Consulting www.boost-consulting.com