David Abrahams wrote:
"Peter Dimov" <pdimov@mmltd.net> writes:
Sean Parent wrote:
This could have been avoided by defining a separate relation for set/map order, either as a function reachable via ADL, or as a function object, then making sure that it is defined for all standard value types.
Why is this necessary? std::less<> serves us well and avoids the whole ADL mess.
std::less is ambiguous. It could be that you wanted merely the function object representation of operator<, or it could be that you wanted the default map/set ordering relation. It is not clear which of the two std::less is supposed to be.
If shared_ptr doesn't support operator< it's not a problem, is it?
The context is: - If we had a separate relation for set/map we would use that for settable/mappable objects. - Why is a separate relation better than just using less<>? - Because it is evident from the design of the standard library that less<> isn't meant for that, not consciously, at least. "What should shared_ptr do" is a separate question. Under the current status quo, it defines operator< to order pair< shared_ptr<>, int > as well. Under a revised standard, it may well need to do something else, depending on how the standard is changed.