这是什么？

这个库旨在成为改进性能或便捷性的迭代器集合。

StepRangeU* 和 StepRangeI*

这些相当于范围，但具有恒定的步长。存在适用于 u8, u32, i8, isize等的变体。

// The odd positive integers from 1 to 1000 the traditional way.
let _ = (1..1000).step_by(2);

// The odd positive integers from 1 to 1000 with a constant step size.
let _ = StepRangeU64::<2>::new(1, 1000);

// If you really want to you can also do this... but don't.
let _ = StepRangeU64::<1>::new(1, 1000).step_by(2);