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#[cfg(test)] mod tests { #[test] fn test_numred() { let mut number: u64 = 12345678901299888; let mut result = super::numred(&number); assert_eq!(9, result); number = 25; result = super::numred(&number); assert_eq!(7, result); } } pub fn numred(number: &u64) -> u8 { let v: Vec<u8> = number .to_string() .chars() .map(|d| d.to_digit(10).unwrap() as u8) .collect(); let mut result: u8 = 0; for i in &v { result = &result + i; if result >= 10 { let r = result as u64; result = numred(&r); } } result }