How does std::views::filter and std::views::transform work under the hood without creating temporary vector allocations like LINQ or JavaScript array methods do?

std::views are non-owning, lazy evaluated iterators! When you write auto result = vec | std::views::filter(isEven) | std::views::transform(square);, no calculations happen until you actually iterate the range. The iterator computes the filter/transform on-the-fly during dereferencing (*it).

They are pure zero-allocation views with zero memory overhead, and the compiler can inline the entire pipeline into a single tight machine loop!