It's pretty much incomprehensible to me too (is it complaining about a missing definition of owner_less? Perhaps it requires some newer version of C++?). But,

It's pretty much incomprehensible to me too (is it complaining about a missing definition of owner_less? Perhaps it requires some newer version of C++?). But, arguing it's a bad choice because the errors are incomprehensible is only a valid argument if you know C++. Otherwise the argument could be had against most programming languages. There are valid arguments why C++ shouldn't be used (I'm of the opinion it should never be used) but this particular problem isn't unique to C++.