> Similarly, the functional abstractions almost feel like a step backwards from the venerable C++ <algorithm>, abstraction and composition-wise. Very nitty-gritty, low-level implementation details leak out like a sieve — you can't have your maps or folds without a generous sprinking of `as_slice()`, `unwrap()`, `iter()` / `iter_mut()` / `into_iter()` and `collect()` everywhere

That's not been my experience at all. In fact I've found <algorithm> to not only be extremely limiting but also being painfully verbose due to the need of begin/end pairs everywhere.