rust solution range_extraction

use std::ops::Add; struct RangeFinder<'a, T: 'a> {    index: usize,    length: usize,    arr: &'a [T],} impl<'a, T> Iterator for RangeFinder<'a, T> where T: PartialEq + Add<i8, Output=T> + Copy {    type Item = (T,  Option<T>);    fn next(&mut self) -> Option<Self::Item> {        if self.index == self.length {            return None;        }        let lo = self.index;        while self.index < self.length - 1 && self.arr[self.index + 1] == self.arr[self.index] + 1 {            self.index += 1        }        let hi = self.index;        self.index += 1;        if hi - lo > 1 {            Some((self.arr[lo], Some(self.arr[hi])))        } else {            if hi - lo == 1 {                self.index -= 1            }            Some((self.arr[lo], None))        }    }} impl<'a, T> RangeFinder<'a, T> {    fn new(a: &'a [T]) -> Self {        RangeFinder {            index: 0,            arr: a,            length: a.len(),        }    }} fn main() {    let input_numbers : &[i8] = &[0,  1,  2,  4,  6,  7,  8, 11, 12, 14,                                  15, 16, 17, 18, 19, 20, 21, 22, 23, 24,                                  25, 27, 28, 29, 30, 31, 32, 33, 35, 36,                                  37, 38, 39];    for (i, (lo, hi)) in RangeFinder::new(&input_numbers).enumerate() {        if i > 0 {print!(",")}        print!("{}", lo);        if hi.is_some() {print!("-{}", hi.unwrap())}    }    println!("");}