Agreed. I thought about it before, and came to a conclusion that the best way to implement it is to use preprocessor constant to allow user specify default separator, e.g. BOOST_PROPERTY_TREE_SEPARATOR.
I disagree. I think this should be a runtime per-tree setting, not something set at compile time. I also think it would be quite trivial to do.
You mean ptree should have additional data member containing default separator? How do we make sure that all nodes in the tree have the same separators? Also, this would add some runtime overhead to the library, storing so many copies of the same character. As an alternative to macro, it could be a part of the traits. But I think this solution is too cumbersome to be practical, because user will need to roll out his own ptree type just to use different default separator. It will also made trees with different separators incompatible. Marcin