SplitWhitespace is a convenience. Its underlying internal type is actually:

    Filter<Split<'a, IsWhitespace>, IsNotEmpty>

The split[1] method is generic, and for example, one can indeed use a regex for it. (I wouldn't use it for CSV though, since it would almost certainly be wrong.)

[1] - https://doc.rust-lang.org/std/primitive.str.html#method.spli...