Re: [boost] [variant] Opinion on boost::safe_get<> and default boost::get<> behavior

On Dec 9, 2014 10:33 AM, "Peter Dimov" wrote:

That's not true. Both get variants can fail (at runtime) if the variant doesn't contain the target, so your code that uses either MUST be prepared to deal with this case. The difference is only that one of them allows you to ask "does this variant contain a Z?" (answering "no"), while the other does not.

Right, but again, this is analogous to something like static_cast allowing you to cast between unrelated types and not telling you until runtime. Perhaps I should have related it to dynamic_cast if that makes things more clear. You need some functionality at run-time, of course, but I don't know if you gain anything tangible by allowing the code to compile for unrelated types for which the conversion is known at compile-time to never be possible. It's hard to say without use-cases, though. I use variants a lot and I don't see this as desirable, but I may have just not encountered a use. If I have an integer long in a variant and I accidentally try to grab an int, I'd certainly like to know at compile-time that the mistake was made.