match on a tuple

Leap
Leap in Rust 
pub fn is_leap_year(year: u64) -> bool {
    match (year % 4, year % 100, year % 400) {
        (_, _, 0) => true,
        (_, 0, _) => false,
        (0, _, _) => true,
        _ => false,
    }
}

A tuple is made from the conditions for the year being evenly divisible by 4, 100 and 400.

  • The tuple is tested in a match expression.
  • It tests from top to bottom, so the (_, _, 0) => true, arm is tested first.
  • It checks the values of the expressions in the tuple, and uses the _ wildcard pattern to disregard a value inside the tuple.
  • If the pattern matches, then the arm returns the value to the right of the =>.
  • If the pattern does not match, then the pattern in the next arm is tested.
  • In the final arm of the match, the wildcard pattern is applied to the entire tuple. This is similar to default used in switch statements in other languages. It returns false no matter what the values in the tuple are.
year year % 4 year % 100 year % 400 is leap year
2020 0 20 20 true
2019 3 19 19 false
2000 0 0 0 true
1900 0 0 300 false

Although some may consider it to be a more "functional" approach, the switch on a tuple approach is somewhat more verbose than other approaches, and may also be considered less readable.

8th May 2024 · Found it useful?

Other Approaches to Leap in Rust

Other ways our community solved this exercise
pub fn is_leap_year(year: u64) -> bool {
    (year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0))
}
Boolean one line

Use one line of boolean conditions. 

pub fn is_leap_year(year: u64) -> bool {
    if year % 100 == 0 {
        year % 400 == 0
    } else {
        year % 4 == 0
    }
}
Ternary operator

Use a ternary expression of boolean conditions. 

use time::{Date, Duration, Month};

pub fn is_leap_year(year: u64) -> bool {
    (Date::from_calendar_date(year as i32, Month::February, 28).unwrap() + Duration::DAY).day()
        == 29
}
Date addition with time crate

Use time::Date addition. 

use chrono::{prelude::*, Duration};

pub fn is_leap_year(year: u64) -> bool {
    (Utc.ymd(year as i32, 2, 28) + Duration::days(1)).day() == 29
}
Date addition with chrono crate

Use chrono::Date addition.