[tialaramex]

Indeed to the extent that Casey has a point here (which sure, I think in its original context it was fine, it's just unfortunate if you mistook a clever quip at a party for a life philosophy) C++ is riddled with types explicitly making this uh, choice.

Its not near the top of the list of reasons std::unordered_map is a crap type, but it's certainly on there. If we choose the capacity explicitly knowing we'll want to put no more than 8340 (key,value) pairs into Rust's HashMap we only allocate once, to make enough space for all 8340 pairs because duh, that's what capacity means. But std::unordered_map doesn't take the hint, it merely makes its internal hash table big enough, and each of the 8340 pairs is allocated separately.