w.r.t. concurrency:
As you know, the difficulty with concurrency is with shared mutable state. Purity simplifies concurrency by restricting mutability; rust simplifies concurrency by restricting sharing.
That makes purity less important for rust.
As you know, the difficulty with concurrency is with shared mutable state. Purity simplifies concurrency by restricting mutability; rust simplifies concurrency by restricting sharing.
That makes purity less important for rust.
Also, note concurrency and parallelism are two of many interesting benefits of purity.
I'll also add unit tests and property testing which are much nicer with purity.