>> It runs about five times slower than the equivalent program > I'd be interested in hearing more about how these were benchmarked. On my machine, they both ru

>> It runs about five times slower than the equivalent program > I'd be interested in hearing more about how these were benchmarked. On my machine, they both run in roughly the same time, with a degree of variance that makes them roughly equivalent. Some runs, the iterator version is faster. It's common to forget to turn on optimizations, which _seriously_ impact Rust's runtimes, LLVM can do wonders here. Generally speaking, if iterators are slower than a loop, that's a bug. In my novice benchmark I found similar results as OP. running 6 tests test for_range_100 ... bench: 89 ns/iter (+/- 2) test for_range_1000 ... bench: 929 ns/iter (+/- 98) test for_range_10000 ... bench: 8815 ns/iter (+/- 414) test for_while_100 ... bench: 36 ns/iter (+/- 3) test for_while_1000 ... bench: 294 ns/iter (+/- 27) test for_while_10000 ... bench: 2768 ns/iter (+/- 268) test result: ok. 0 passed; 0 failed; 0 ignored; 6 measured https://gist.github.com/simonz05/afd76c549d6c8afb8081 https://gist.github.com/simonz05/afd76c549d6c8afb8081