> I was under the impression that it was supposed to be the functional systems programming alternative.
The elevator pitch is "Speed of C++, safety of ML, concurrency of Erlang."
The elevator pitch is "Speed of C++, safety of ML, concurrency of Erlang."
(Is concision really what you lose when you need explicit looping constructs? Maybe "abstraction capability"?)
Did you mean something other than combinators?
For example, above, you mention how TCO lets you use first-class functions to help you eliminate mutability. It's the elimination of mutability that's the safety here. Rust allows you to eliminate mutability through other means.
So support for tail calls is not about safety but expressiveness, and Rust chooses to express iterative algorithms through other means, such as the iteration protocol that's built on top of higher-order functions.
EDIT: Maybe I'm misreading you and you only mean the imperative nature of loops forces you to use mutation. Rust does not eschew mutation altogether. Even as a functional programmer myself, I'd argue pretty emphatically that mutation, particularly of local variables, is not a grave safety concern.