Does anyone have information on using operator""?

Question

Bjarne Stroustrup gave a keynote presentation today for the Going Native 2012 conference. In his presentation, he discussed the issue of enforcing correct units. His elegant (IMHO) solution to this involved using an operator I have never heard of before: operator"". Using this operator, he was able to write C++ code that looked like this:

ratio = 100m / 1s; 

Where operator""m(...) and operator""s(...) were defined.

Does anyone know of any documentation regarding how to actually use this operator (or even if any modern C++ compilers support it)? I tried searching online, but had no luck. Any help would be greatly appreciated.

Answer 1

The syntax you'd be looking for is "user-defined literals" which is a feature of C++11.

g++ versions 4.7 and better support this feature.

Here is some documentation describing the use of that operator overload: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2765.pdf

Also see the excellent link Xeo provides in the comments to your question.

Answer 2

Currently the best documentation is probably in the standard itself. You can get the latest version from the commitee's site. According to gcc's site it will be in the next revision of gcc (gcc-4.7). You should be able to test it when building gcc from the SVN repository.